Università di Pisa
Dipartimento di Scienze Agrarie, Alimentari e
Agro-ambientali
CORSO DI LAUREA MAGISTRALE IN PROGETTAZIONE E
GESTIONE DEL VERDE URBANO E DEL PAESAGGIO
TESI DI LAUREA MAGISTRALE
Effects of UV-B radiation on 5 cool-season
turfgrasses
RELATORE:
CANDIDATO:
Prof.Marco Volterrani
Dilinu Wali
CORRELATORE:
Effects of UV-B radiation on 5 cool-season
turfgrasses
Abstract
Light intensity affects the growth rate of plants. Adverse environmental factors, including UV-B radiation, may affect plants growth. Over the last decades numerous studies have been published on the effect of UV-B radiation on plants. In a vast major majority, these studies concern cultivated plants, while only a few experiments have involved turfgrasses. Therefor we have chosen some most used cool-season turfgrass to infer this area. As a result of changes in contents of chloroplast pigments are evidences of high UV-B radiation tolerance of analyzed plants. Photosynthetic pigments mainly constitute of chlorophyll a, b and carotenoids are of vital importance in photosynthesis changes. The contents of chloroplast pigments are evidences of UV-B radiation tolerance of five analyzed plant species which are Agrostis stolonifera, Festuca arundinaceae, Poa pratensis, Poa supina, Lolium perenne. The results of the test showed some differences between the species regarding the response to UV-B exposure, especially for the number of tillers the Agrostis stolonifera species increases the number with the increase in exposure, for other parameters the responses of species are less obvious. Chlorophyll content and carotenoids, although generally tend to decrease, seem to be dependent on species.
Keywords
Agrostis stolonifera, Festuca arundinaceae, Poa pratensis, Poa supina, Lolium perenne, UV-B, plant growth, chlorophyll a, chlorophyll b, carotenoids.
Index
1. Introduction 3
1.1. The solar radiation 3
1.1.1. Sun light division and effects 3
1.1.2. Life on earth and sun light 14
1.1.3. Sun light and Photosynthesis 15
1.1.4. UV impacts on plants 21
1.1.5. Plants and UVB radiation 22
1.2. Turfgrass 23
1.2.1. General explanation about turfgrass 23
1.2.2. Some of the benefits of turfgrass 24
1.3 Aim of the research 28
2. Material and methods 28
2.1 Plant material 28
2.2. Methods 30
3.1 UV-B treatment results 34
3.2 Bio-metric experiment results 36
4. Discussion and conclusion 40
1. Introduction
1.1 The solar radiation
1.1.1. Sunlight division and effects
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon. When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. When it is blocked by clouds or reflects off other objects, it is experienced as diffused light. The World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter. (World Meteorological Organization，2008) Other sources indicate an "Average over the entire earth" of "164 Watts per square meter over a 24 hour day". http://zebu.uoregon.edu/disted/ph162/l4.html)
Figure 1. Three types of UV rays (UVA, UVB, UVC) emitted from the sun to the earth. http://www.open.edu/openlearn/nature-environment/natural-history/rough-science-carriacou-make-sunblock-challenge#
Figure 2. Division of the light spectrum. (http://www.aquaticplantcentral.com/forumapc/lighting/38014-lighting-spectrum-photosythesis. html)
"Ultraviolet" means "beyond violet" (from Latin ultra, "beyond"), violet being the color of the highest frequencies of visible light. Ultraviolet has a higher frequency than violet light.
UV radiation was discovered in 1801 when the German physicist Johann Wilhelm Ritter observed that invisible rays just beyond the violet end of the visible spectrum
darkened silver chloride-soaked paper more quickly than violet light itself. He called them "oxidizing rays" to emphasize chemical reactivity and to distinguish them from "heat rays", discovered the previous year at the other end of the visible spectrum. The simpler term "chemical rays" was adopted shortly thereafter, and it remained popular throughout the 19th century, although there were those who held that these were an entirely different sort of radiation from light (notably John William Draper, who named them "tithonic rays". (Draper, 1842; 1844). The terms chemical and heat rays were eventually dropped in favor of ultraviolet and infrared radiation
respectively. (Beeson and Mayer, 2007) (Hockberger, 2002) In 1878 the effect of
short-wavelength light on sterilizing bacteria was discovered. By 1903 it was known the most effective wavelengths were around 250 nm. In 1960, the effect of
ultraviolet radiation on DNA was established. (Bolton and Colton, 2008)
The discovery of the ultraviolet radiation below 200 nm, named vacuum ultraviolet because it is strongly absorbed by air, was made in 1893 by the German physicist
Victor Schumann.(Lyman, 1914)
Table 1. The electromagnetic spectrum of ultraviolet radiation (UVR), defined most broadly as 10 – 400 nanometers, can be subdivided into a number of ranges. (https://en.wikipedia.org/wiki/Ultraviolet)
The shorter bands of UVC, as well as even more-energetic UV radiation produced by the Sun, are absorbed by oxygen and generate the ozone in the ozone layer when single oxygen atoms produced by UV photolysis of dioxygen react with more dioxygen. The ozone layer is especially important in blocking most UVB and the remaining part of UVC not already blocked by ordinary oxygen in air.
Figure 3. Levels of ozone at various altitudes and blocking o different bands of ultraviolet radiation. In essence, all UV-C is blocked by diatomic oxygen (100-200 nm) or by ozone (triatomic
oxygen) (200-280 nm) in the atmosphere. The ozone layer then blocks most UV-B. Meanwhile, UV-A is hardly affected by ozone, and most of it reaches the ground. UV-A makes up almost all of the 25% of the Sun’s total UV that penetrates the earth’s atmosphere. https://en.wikipedia.org/wiki/Ultraviolet
The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a principal source of vitamin D3 and a mutagen. Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun. A photon starting at the center of the Sun and changing direction every time it encounters a charged particle would take between 10.000 and 170.000 years to get to the surface.
(NASA,2012https://sunearthday.nasa.gov/2007/locations/ttt_sunlight.php)
Sunlight is a key factor in photosynthesis, the process used by plants and other autotrophic organisms to convert light energy, normally from the Sun, into chemical energy that can be used to fuel the organisms' activities.
The spectrum of the Sun solar radiation is close to that of a black body (Appleton and
Barnett, 1945) (Iqbal, 1983) with a surface temperature of about 5.800 Kelvins. (NASA, 2011) The Sun emits EM radiation across most of the electromagnetic spectrum. Although the Sun produces gamma rays as a result of the nuclear-fusion process, internal absorption and thermalization convert these super-high-energy photons to lower-energy photons before they reach the Sun's surface and are emitted out into space. As a result, the Sun does not emit gamma rays from this
process, but it does emit gamma rays from solar flares. (http://www.nasa.gov/mission_pages/GLAST/news/highest-energy.html) The Sun also emits X-rays, ultraviolet, visible light, infrared, and even radio waves. (http://www.nasa.gov/mission_pages/GLAST/news/highest-energy.html)
The only direct signature of the nuclear process is the emission of neutrinos. Although the solar corona is a source of extreme ultraviolet and X-ray radiation, these rays make up only a very small amount of the power output of the Sun (see spectrum at right). The spectrum of nearly all solar electromagnetic radiation striking the Earth's atmosphere spans a range of 100 nm to about 1 mm (1.000.000 nm). (http://www.energiasustentables.com.ar/energia%20solar-en/fundamentos%20adici onales-en.html) This band of significant radiation power can be divided into five
regions in increasing order of wavelengths: (Mark and Kevin, 1995)
Ultraviolet C or (UVC) range, which spans a range of 100 to 280 nm. The term
ultraviolet refers to the fact that the radiation is at higher frequency than violet light (and, hence, also invisible to the human eye). Due to absorption by the atmosphere very little reaches Earth's surface. This spectrum of radiation has germicidal properties, as used in germicidal lamps.
Ultraviolet B or (UVB) range spans 280 to 315 nm. It is also greatly absorbed by the
Earth's atmosphere, and along with UVC causes the photochemical reaction leading to the production of the ozone layer. It directly damages DNA and causes sunburn,
and Holick, 2013)
Ultraviolet A or (UVA) spans 315 to 400 nm. This band was once held to be less
damaging to DNA, and hence is used in cosmetic artificial sun tanning (tanning booths and tanning beds) and PUVA (psoralen and ultraviolet A therapy) therapy for psoriasis. However, UVA is now known to cause significant damage to DNA via indirect routes (formation of free radicals and reactive oxygen species), and can cause cancer
(https://web.archive.org/web/20130131164352/http://www.cancer.gov/newscenter /entertainment/tipsheet/tanning-booths)
Visible range or light spans 380 to 780 nm. As the name suggests, this range is visible
to the naked eye. It is also the strongest output range of the Sun's total irradiance spectrum.
Infrared range that spans 700 nm to 1.000.000 nm (1 mm). It comprises an
important part of the electromagnetic radiation that reaches Earth. Scientists divide the infrared range into three types on the basis of wavelength:
Infrared-A: 700 nm to 1.400 nm Infrared-B: 1.400 nm to 3.000 nm Infrared-C: 3.000 nm to 1 mm.
The solar constant, a measure of flux density, is the amount of incoming solar electromagnetic radiation per unit area that would be incident on a plane
perpendicular to the rays, at a distance of one astronomical unit (AU) (roughly the mean distance from the Sun to Earth). The "solar constant" includes all types of solar radiation, not just the visible light. Its average value was thought to be approximately 1366 kW/m2, (Satellite observations of total solar irradiance http://acrim.com/TSI%20Monitoring.htm) varying slightly with solar activity, but recent recalibrations of the relevant satellite observations indicate a value closer to
1361 kW/m² is more realistic. (Kopp and Lean, 2011)
Total solar irradiance (TSI) – the amount of solar radiation received at the top of Earth's atmosphere – has been measured since 1978 by a series of overlapping NASA and ESA satellite experiments to be 1.361 watts per square meter (W/m ² ). (Satellite observations of total solar irradiance http://acrim.com/TSI%20Monitoring.htm)(Willson and Mordvinov, 2003) (FRÖHLICH, 2005) TSI observations are continuing today with the ACRIMSAT/ACRIM3, SOHO/VIRGO and SORCE/TIM satellite experiments. Variation of TSI has been discovered on many timescales including the solar magnetic cycle and many shorter periodic cycles. (http://www.acrim.com/TSI%20Monitoring.htm) TSI provides the energy that drives Earth's climate, so continuation of the TSI time series database is critical to understanding the role of solar variability in climate change.
Spectral solar irradiance (SSI) – the spectral distribution of the TSI – has been monitored since 2003 by the SORCE Spectral Irradiance Monitor (SIM). It has been found that SSI at UV (ultraviolet) wavelength corresponds in a less clear, and probably more complicated fashion, with Earth's climate responses than earlier
assumed, fueling broad avenues of new research in “the connection of the Sun and stratosphere, troposphere, biosphere, ocean, and Earth ’ s climate. (Stuiver and Braziunas, 1993)
Different bodies of the Solar System receive light of an intensity inversely proportional to the square of their distance from Sun. A rough table comparing the
amount of solar radiation received by each planet in the Solar System follows (World
Meteorological Organization，2008)
Table 2. Different planets receive different amounts of solar radiation. https://en.wikipedia.org/wiki/Sunlight#Solar_constant
The Sun's electromagnetic radiation which is received at the Earth's surface is predominantly light that falls within the range of wavelengths to which the visual
systems of the animals that inhabit Earth's surface are sensitive. The Sun may therefore be said to illuminate, which is a measure of the light within a specific sensitivity range. Many animals (including humans) have a sensitivity range of
approximately 400–700 nm, (Buser and Michel, 1992) and given optimal conditions
the absorption and scattering by Earth's atmosphere produces illumination that
approximates an equal-energy illuminant for most of this range. (MacEvoy and Bruce,
2008). The useful range for color vision in humans, for example, is approximately 450
– 650 nm. Aside from effects that arise at sunset and sunrise, the spectral
composition changes primarily in respect to how directly sunlight is able to illuminate.
When illumination is indirect, Rayleigh scattering
(https://it.wikipedia.org/wiki/Scattering_di_Rayleigh) in the upper atmosphere will lead blue wavelengths to dominate. Water vapor in the lower atmosphere produces further scattering and ozone, dust and water particles will also absorb selective
wavelengths. (Wyszecki and Stiles, 1967; MacAdam, 1985).
On Earth, the solar radiation varies with the angle of the sun above the horizon, with longer sunlight duration at high latitudes during summer, varying to no sunlight at all in winter near the pertinent pole. When the direct radiation is not blocked by clouds, it is experienced as sunshine. The warming of the ground (and other objects) depends on the absorption of the electromagnetic radiation in the form of heat. The amount of radiation intercepted by a planetary body varies inversely with the square of the distance between the star and the planet. The seasonal and latitudinal distribution and intensity of solar radiation received at Earth's surface does vary.
(Museum.state.il.US, 2007). The effect of sun angle on climate results in the change in solar energy in summer and winter. For example, at latitudes of 65 degrees, this can vary by more than 25% as a result of Earth's orbital variation. Because changes in winter and summer tend to offset, the change in the annual average insolation at any given location is near zero, but the redistribution of energy between summer and winter does strongly affect the intensity of seasonal cycles. Such changes associated with the redistribution of solar energy are considered a likely cause for the coming and going of recent ice ages.
Space-based observations of solar irradiance started in 1978. These measurements show that the solar constant is not constant. It varies on many time scales, including the 11-year sunspot solar cycle. When going further back in time, one has to rely on irradiance reconstructions, using sunspots for the past 400 years or cosmogenic radionuclides for going back 10.000 years. Such reconstructions have been done. (Wang and Lean, 2005) (Steinhilber, 2009) (Vieira and Eduardo, 2011) (Steinhilber and Abreu, 2012)These studies show that in addition to the solar irradiance variation
with the solar cycle the “Schwabe”cycle or solar cycle.
(https://en.wikipedia.org/wiki/Solar_cycle), the solar activity varies with longer cycles, such as the proposed 88 year (Gleisberg cycle), 208 year (DeVries cycle) and 1.000 year (Eddy cycle).
1.1.2. Life on earth and sun light
The existence of nearly all life on Earth is fueled by light from the Sun. Most autotrophs, such as plants, use the energy of sunlight, combined with carbon dioxide and water, to produce simple sugars, a process known as photosynthesis. These sugars are then used as building-blocks and in other synthetic pathways that allow the organism to grow.
Heterotrophs, such as animals, use light from the Sun indirectly by consuming the products of autotrophs, either by consuming autotrophs, by consuming their products, or by consuming other heterotrophs. The sugars and other molecular components produced by the autotrophs are then broken down, releasing stored solar energy, and giving the heterotroph the energy required for survival. This
process is known as cellular respiration.
(https://en.wikipedia.org/wiki/Sunlight#Life_on_Earth)
In prehistory, humans began to further extend this process by exploiting plant and animal materials for other uses. They used animal skins for warmth, for example, or wooden weapons to hunt. These skills allowed humans to harvest more of the sunlight than was possible through glycolysis alone, and human population began to grow.
During the Neolithic Revolution, the domestication of plants and animals further increased human access to solar energy. Fields devoted to crops were enriched by inedible plant matter, providing sugars and nutrients for future harvests. Animals
that had previously provided humans with only meat and tools once they were killed were now used for labor throughout their lives, fueled by grasses inedible to humans. (https://en.wikipedia.org/wiki/Sunlight#Life_on_Earth)
The more recent discoveries of coal, petroleum and natural gas are modern extensions of this trend. These fossil fuels are the remnants of ancient plants and animal matter, formed using energy from sunlight and then trapped within Earth for millions of years. Because the stored energy in these fossil fuels has accumulated over many millions of years, they have allowed modern humans to massively increase the production and consumption of primary energy. As the amount of fossil fuel is large but finite, this cannot continue indefinitely, and various theories exist as to what will follow this stage of human civilization (e.g., alternative fuels, Malthusian
catastrophe, new urbanism, peak oil).
(https://en.wikipedia.org/wiki/Sunlight#Life_on_Earth)
1.1.3. Sun light and Photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities (energy transformation).
Most plants, most algae and cyanobacteria perform photosynthesis, such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies all of the
organic compounds and most of the energy necessary for life on Earth. (Bryant and Frigaard, 2006)
Photosynthesis occurs in two stages. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the energy-storage molecules ATP and NADPH. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide.
Most organisms that utilize oxygenic photosynthesis use visible light for the light-dependent reactions, although at least three use shortwave infrared or, more
specifically, far-red radiation.
(http://www.bio-medicine.org/biology-news/Scientists-discover-unique-microbe-in-C alifornias-largest-lake-203-1/)
Some organisms employ even more radical variants of photosynthesis. Some archea use a simpler method that employs a pigment similar to those used for vision in animals. The bacteriorhodopsin changes its configuration in response to sunlight, acting as a proton pump. This produces a proton gradient more directly, which is then converted to chemical energy. The process does not involve carbon dioxide fixation and does not release oxygen, and seems to have evolved separately from the
more common types of photosynthesis. (Ingrouille and Eddie, 2006)(Anthony and
Larkum, 2007)
In the light-dependent reactions, one molecule of the pigment chlorophyll absorbs one photon and loses one electron. This electron is passed to a modified form of
chlorophyll called pheophytin, which passes the electron to a quinone molecule, starting the flow of electrons down an electron transport chain that leads to the ultimate reduction of NADP to NADPH. In addition, this creates a proton gradient (energy gradient) across the chloroplast membrane, which is used by ATP synthase in the synthesis of ATP. The chlorophyll molecule ultimately regains the electron it lost when a water molecule is split in a process called photolysis, which releases a
dioxygen (O2) molecule as a waste product.
The overall equation for the light-dependent reactions under the conditions of
non-cyclic electron flow in green plants is: (Raven and Eichhorn, 2005)
2 H2O + 2 NADP+ 3 ADP + 3 Pi + light → 2 NADPH + 3 ATP + O2
Not all wavelengths of light can support photosynthesis. The photosynthetic action spectrum depends on the type of accessory pigments present. For example, in green plants, the action spectrum resembles the absorption spectrum for chlorophylls and carotenoids with absorption peaks in violet-blue and red light. In red algae, the action spectrum is blue-green light, which allows these algae to use the blue end of the spectrum to grow in the deeper waters that filter out the longer wavelengths (red light) used by above ground green plants. The non-absorbed part of the light spectrum is what gives photosynthetic organisms their color (e.g., green plants, red algae, purple bacteria) and is the least effective for photosynthesis in the respective organisms.
–6%. (Miyamoto, 2009)Absorbed light that is unconverted is dissipated primarily as
heat, with a small fraction (1 – 2%) (Maxwell and Johnson, 2000) re-emitted as
chlorophyll fluorescence at longer (redder) wavelengths. A fact that allows measurement of the light reaction of photosynthesis by using chlorophyll
fluorometers. (Maxwell and Johnson, 2000)
Actual plants' photosynthetic efficiency varies with the frequency of the light being converted, light intensity, temperature and proportion of carbon dioxide in the
atmosphere, and can vary from 0.1% to 8%. (Robert, 2002). By comparison, solar
panels convert light into electric energy at an efficiency of approximately 6–20% for mass-produced panels, and above 40% in laboratory devices.
Figure 4. Absorbance spectra of free chlorophyll a (green) and b (red) in a solvent. The action spectra of chlorophyll molecules are slightly modified in vivo depending on specific
pigment-protein interactions
The process of photosynthesis provides the main input of free energy into the biosphere, and is one of four main ways in which radiation is important for plant life. (Jones, 2014)
The radiation climate within plant communities is extremely variable, with both time and space. In the early 20th century, Frederick Blackman(25 July 1866 – 30 January 1947 ) and Gabrielle Matthaei ( 3 October 1876 – 18 August 1930) investigated the effects of light intensity (irradiance) and temperature on the rate of carbon assimilation. (https://en.wikipedia.org/wiki/Photosynthesis)
At constant temperature, the rate of carbon assimilation varies with irradiance, increasing as the irradiance increases, but reaching a plateau at higher irradiance. At low irradiance, increasing the temperature has little influence on the rate of carbon assimilation. At constant high irradiance, the rate of carbon assimilation increases as the temperature is increased.
These two experiments illustrate several important points: First, it is known that, in general, photochemical reactions are not affected by temperature. However, these experiments clearly show that temperature affects the rate of carbon assimilation, so there must be two sets of reactions in the full process of carbon assimilation. These are, of course, the light-dependent 'photochemical' temperature-independent stage, and the light-independent, temperature-dependent stage. Second, Blackman's experiments illustrate the concept of limiting factors. Another limiting factor is the wavelength of light. Cyanobacteria, which reside several meters underwater, cannot
receive the correct wavelengths required to cause photoinduced charge separation in conventional photosynthetic pigments. To combat this problem, a series of proteins with different pigments surround the reaction center. This unit is called a phycobilisome.
There are many factors effect on plant growth and propagation for example nutrients, water stress, type of soil, environment pollution etc, among those factors sun light also silently effecting plants.
The solar radiation spectrum or light intensity has a very important influence on plant growth and development, which directly affects the photosynthesis of plants. In a certain light intensity range, if other conditions are met, when the light intensity increases, the intensity of photosynthesis also increases. But if the light intensity exceeds the saturation point of light and the light intensity increases, the photosynthesis intensity does not increase. If Light intensity is too strong, it will destroy the protoplasm, causing chlorophyll decomposition, or excessive dehydration of cells leaving stomatal closure, resulting in reduced photosynthesis, or even in the process to stop. When the light intensity is weak, plant photosynthesis produces organic matter less than the consumption of respiration and the plant will stop growing. Only when the light intensity meets the requirements of photosynthesis,
the plant can have a normal growth and development.
(http://www.fondriest.com/environmental-measurements/parameters/weather/phot osynthetically-active-radiation/)
Visible light is an important raw material for photosynthesis of green plants. Green plant chlorophyll uptake is mostly red and orange light, followed by blue-violet light and the absorption of yellow-green light at least.
1.1.4. UV impacts on plants
UV has a different impact on plants, Long ultraviolet rays have a stimulating effect on plant growth, can increase crop yield, promote protein, sugar, acid synthesis. When irradiating seeds with long ultraviolet light, it can improve the seed germination. On the other hand short ultraviolet light has an inhibitory effect on plant growth, can prevent plants excessive growth, have effect of disinfection and sterilization, also reduce plant diseases.
Sudden changes of light intensity, will make the leaves become yellow, can cause plant growth weakened, or even death, so if saplings suffer so much of strong light, the trees may occur this phenomenon. UV could also increase the formation of special forms of plants, with short stems, shrink foliage, fluffy development, increased chlorophyll content, anthocyanins content in stems and leaves, particularly bright color. UV is not the necessary wavelength for plants to survive. After all, photosynthesis does not require ultraviolet light. However, plants (at least part of plants) still need to absorb a certain amount of UV radiation in order to have a more normal growth. The main role of ultraviolet light for plants is to participate in the process of plant development, regulating photomorphogenesis process. Recently
more and more attentions are given to predicting the impacts of increased UV-B. (Dekmyn and Impens. 19981999) on grass species.
1.1.5. Plants and UVB radiation
The increase of UV-B (280–315 nm) radiation, is due to ozone depletion and have been a cause for concern for many years (Webb, 1997). Many studies concerning the possible effects of UV-B on growth and metabolism have been made (Teramura and Sullivan, 1994; Bjorn, 1996).
UV-B effects can be divided into two categories:
Damaging effects on photosynthesis and growth, that are only found on sensitive species or under high UV-B doses (often in combination with unnaturally low photosynthetically active radiation (PAR) doses);
Photomorphogenic effects, such as changes in plant height, branching, leaf weight ratio and root:shoot ratio (Dumpert and Knacker, 1985; Barnes et al., 1996).
Although the mechanism for these reactions is not yet understood there are indications that specific UV-B photoreceptor(s) may be responsible (Jenkins, 1997). The sensitivity of species is partially explained by their ability to respond to UV-B by increasing the level of protective pigments or leaf thickness (Tevini et al., 1991; Day, 1993; Caasi-Lit et al., 1997). Differences in DNA repair or plant architecture may also be important in determining the sensitivity to UV-B.
In several studies carried out UV-B effects are not linear (Gwynn-Jones and Johanson, 1996). Little attention has been paid to possible effects of UV-B on grass species, except for some studies on natural dune grassland in the Netherlands, showing increases in biomass production and changes in leaf angle and plant morphology in response to increased UV-B (Tosserams and Rozema, 1995) (Tosserams et al.,1997) and a study on subarctic grass species showing reduced biomass at moderately enhanced UVB but no effects at high UV-B (Gwynn-Jones and Johanson, 1996). Several studies on grain crop shave indicated that these species are generally quite resistant to UV-B, but the results are species-and cultivar-dependent. Studies on rye have indicated that this grass is sensitive even at lowUV-B intensities (Deckmynand Impens, 1997).
1.2. Turfgrass
1.2.1. General explanation about turfgrass
"Turfgrass" signifying a more quality "grass" than one that is simply a lawn grass. All this means that there are grasses and there are turfgrasses. (http://turfgrasses.com/) Turfgrass is a type of grass that you can see growing in golf courses, sports fields and playgrounds. The turfgrass differs from the ornamental grass varieties. They are thicker, stronger and grow in dense patches carpeting the ground. Point in fact, turfgrasses may be one of the oldest techniques humans have used to enhance their external living environment. (Beard. J.B 1989)
Turfgrasses have numerous important functions as well as being both aesthetically attractive and important outdoor recreational surfaces. These important beneficial characteristics, which are summarized in Figure 7, contribute to our quality of life and are too often overlooked.
Table 3. Turfgrass benefits. (From J.B.Beard, 1989)
1.2.2. Some of the benefits of turfgrass.
Some of the benefits that Turfgrass provides include converting carbon dioxide into oxygen, absorbing pollutants from run-off and protecting soil from wind and water absorption among several others.
*Soil Erosion and Dust Stabilization.
Turfgrasses are one of the more inexpensive, durable ground covers. They offer a cost effective method to control wind and water erosion of soil, thereby protecting a valuable, non-renewable soil resource. For example, studies have shown the comparative soil sediment loss from a very intense 3-inch-perhour rainfall to be 199 lbs./acre from bare cropland, whereas the loss from a turfgrass cover was only 15% as much (Gross et al., 1991). Note that rains of this intensity are rare. Most rains in the more normal range of 1 inch or less are characterized by negligible sediment loss from turfgrass areas.
*Water Entrapment, Groundwater Recharge and Flood Control.
Mowed turfgrass typically ranges from 30 million to greater than 8 billion shoots per acre (Beard, 1973); A shoot density of over 26 billion is found on closely mowed putting greens. The closer the mowing height, the higher the shoot density. This dense plant canopy of mowed turf is one of the most effective systems in the entrapment of water and water-borne particulate matter and chemicals. The large amount of water runoff that occurs from impervious surfaces, such as asphalt, concrete, and roofs in urban areas, carries many pollutants in the runoff water that are trapped in the turf canopy, thereby protecting the quality of surface waters. The dense turfgrass canopy that acts essentially as a sponge also greatly reduces the intensity of runoff water shortly after rains, thereby holding water in place to increase the rate of groundwater recharge and reducing the rate and amount of
runoff water, thereby decreasing the need to invest in expensive man-made flood-control structures.
*Carbon Storage.
A grassland ecosystem is well known for its high soil organic matter levels in comparison to woodland areas. A high proportion of the world's most fertile soil was formed under a grass ecosystem. The very unique extensive, fibrous root system of turfgrasses contributes substantially to soil improvement through organic matter additions from decomposing roots and underground stems, which have an estimated turnover rate of 42%. For turfgrass, 66% of the annual net productivity of plant biomass is below grown (Falk, 1967). Thus, turfs function in carbon storage via conversion of carbon dioxide emissions to soil organic matter. They also serve a vital function in restoration of environmentally damaged lands.
*Organic Chemical and Pesticide Degradation.
Turfgrasses have a unique, fibrous root system that is continually being replaced. This dynamic decomposition process supports a large, diverse population of soil microflora and microfauna. Many irrigated turfgrass areas would have microbial populations that are even larger. The turfgrass-soil ecosystem with its large microorganism population offers one of the most active biological systems for degradation of trapped organic chemicals and pesticides, thereby functioning in the protection of groundwater quality.
The transpirational cooling capabilities of turfs have a significant cooling impact on the micro-environment. Urban areas tend to be 10 to 12°F warmer than adjacent rural areas. Thus, the higher the percentage of turfgrass areas in urban communities relative to impermeable surfaces, the less the heat island effect.
*Reduction in Noise and Glare.
Significant noise abatement can be achieved through the use of turfgrasses. For example, a 4-inch-high turfgrass area along a road reduces vehicle noise levels by 40% in a distance of 70 feet (Cook et al., 1971). This noise abatement is further accentuated by a combination of turfs, trees, and shrubs. By the same token, the multidirectional reflection of turfgrasses significantly reduces the discomfort of visual glare effects on the human eye.
*Reduced Fire Hazard and Enhanced Security.
The living green space of irrigated turf, parks, golf courses, and residential lawns provides a significant green space of low fuel value that is vital as a fire break, particularly in areas that experience extended summer droughts (Youngner, 1970). Also, mowed turfs provide a high-visibility zone that restricts the activities of unwanted intruders.
*Recreational Benefits.
Turfgrasses enhance the physical health of sports and recreational participants. Turfs also provide a resilient cushion that minimizes injuries.
1.3 Aim of the research
In more recent times there have been some studies of the effects of solar UV-B on terrestrial plants. (Dekmyn and Impens, 1998; 1999) (Dipayan.S et al; 2011) (Yuen.G.Y 2002) (Dekmyn and Impens. 1998 May) Some important questions remain unanswered about UV-B impacts on the physiology of turfgrass in their natural environment.
The research aimed to investigate the physiological and morphological response of
Agrostis stolonifera, Festuca arundinaceae, Poa pratensis, Poa supina, Lolium perenne at different exposition to UVB radiation (from 0 to 16 days).
2. Material and methods
2.1 Plant material
Poa pratensis L.
Common name Kentucky Bluegrass. Which is a popular lawn grass and has more than 200 varieties. Kentucky Bluegrass is very sturdy and can withstand pressure due to constant walking or running. This turfgrass grows well in fall and spring when the temperatures are cold, and the climate is pleasant. Kentucky Bluegrass has a smooth texture with rich green color. The root system of the Kentucky Bluegrass is
drought tolerance capacity. It can become dormant when there is a scarcity of water and can spring back to life whenever it is watered. This grass is suitable for
residential lawns, parks and athletic fields and golf fairways. It is also grown as pasture for horse, cattle and sheep.
Lolium perenne L.
Common name Perennial Ryegrass is a bunch type turfgrass that is dark green in color with smooth to medium texture. Perennial Ryegrass is a cool-season grass that grows well in regions that have moderate temperatures throughout the year. It can tolerate cold temperatures very well. The leaves are dark green and have a smooth, glossy lower surface. There are prominent parallel veins running across the upper surface of the leaves. The Perennial Ryegrass has a thick taproot system with a single main root with branches extending on either side. It is suited for home lawns, parks, playgrounds, golf courses and sports fields.
Agrostis stolonifera L.
Also called creeping bentgrass, the ability of creeping bentgrass to remain palatable and green in the summer is valued for livestock forage; it also provides good cover for upland game birds and waterfowl. It is used for turf in gardens and landscapes, particularly on golf courses. (Esser and Lora. 1994)
Festuca arundinacea Schreb.
Is a species of grass commonly known as tall fescue. Tall fescue can be found
growing in most soils of the southeast including marginal, acidic, and poorly drained soils and in areas of low fertility, and where stresses occur due to drought and overgrazing. (Forage identification and use guide) (Garry Lacefield et al. 2000)
Poa supina Schrad.
Known as bluegrass. The vivid green leaves are short and blunt at the tips, shaped like the prow of a small canoe. They are soft and drooping. Long sheaths clasp the stem. The leaves are smooth above and below, with finely serrated edges. It occurs as a common constituent of lawns, where it is also often treated as a weed, and grows on waste ground. Many golf putting greens, including the famously fast Oakmont Country Club greens. (Dvorchak.R. 2007)
2.2. Methods
The trial was carried out at the Department of Agriculture, Food and Environment of Pisa University.
The species Agrostis Stolonifera, Festuca Arundinaceae, Poa Pratensis, Poa Supina, Lolium Perenne were seeded in peat-filled honeycomb alveoli (7 cm2). The trial was
carried out from the 20th of April to the 30th of May 2016. On 20thApril 2016 (Time
exposition ranged from T0 to T16 (T0 is the no treatment time and T16 is the maximum exposure time), in all cased the pots were irrigated every two days and without moving.
UV-B treatment :
This part of experiment aimed to assess the impacts of UV-B radiation over a 16-day period on vitality and levels of pigments (chlorophyll a, b and carotenoids). The trial
was carried out from the 20thof April 2016 for 16 days.
Two climatic chambers were set to the following conditions: 12 h photoperiod,
temperature 22 ± 1 ºC, relative humidity 75% and PPFD 100 µmol m-2s-1. One of the
chambers was equipped with three UVB-emitting lamps (Philips TL 20W/01RS UVB Narrowband, Koninklijke Philips Electronics, Eindhoven, The Netherlands) providing
1.69 W m-2at the tops of the plants (about 45 cm under the lamps). Pots of plants
were randomly distributed into the chambers and acclimated for 1 day. After acclimation, plants were UVB irradiated for 120 min at the middle of the photoperiod. Leaves were collected and immediately frozen in liquid nitrogen and stored at -80 ºC for the biochemical analyses.
Pigments assay
Pigments were extracted by incubating tissues (50mg) in 1.5 ml 80% acetone for 1 week at 48C in darkness. The absorbance of extracts was measured spectrophotometrically at 470.0, 663.2, and 648.8 nm. These absorbance values
were used for calculation of chlorophyll a, chlorophyll b, and total carotenoids contents by means of formulae suggested by Lichtenthaler and Wellburn (1983) and Wellburn (1994).
Biometric evaluations:
Final bio-metric parameters evaluated on 30 May 2016 at the end of the trial Tillers n°(direct counting with data reported as tillers nocm-2)
Leaf width and leaf length: measured with a precision Vernier caliper on 20 fully expanded leaves per honeycomb
One leaf mean surface (mm2)
Total leaf fresh weight (after cutting of plants and reported as g cm-2)
Total leaf dry weight (g cm-2): plants were dried at least 72 h at 60◦C, then
later weighed
Plants growth in the trial period (turf height was measured with a ruler at the beginning and at the end of the trial, the growth was reported as cm)
Turf color (with a rating scale of 1=light green and 9= dark green): visual
Figure 5, Faculty greenhouse.
Figure 6, Overall look from the last day (T16) of treatment.(From right to left Agrostis Stolonifera, Festuca Arundinaceae, Poa Pratensis,Lolium Perenne, Poa Supina)
Data were subject to analysis of variance using CoStat 6.400 (CoHortSoftware, Monterey, CA). Fisher’s protected least significant difference at a 5% probability level was used to compare means among exposition periods for each species separately.
3.Results
3.1. Results of UV-B treatment
The contents of chlorophylls and the carotenoids varied considerably.
Chlorophyll a:
Poa Supina(Ps) showed the significant decrease of chlorophyll a content, from T0: 1545.30 ug/gFW to T16: 490.18 ug/gFW. (Figure 7)
Lolium Perenne(Lp) has decreased from T0:996.65 ug/gFW to T16: 534.32 ug/gFW, at T2 there was a slight increasment 1025.77 ug/gFW.
Poa Pratensis(Pp) has decreased from T0:1507.69 ug/gFW to T16: 828.94 ug/gFW. Festuca Arundinaceae(Fa) has decreased from T0:1601.89 ug/gFW to T16: 845.14 ug/gFW.
Agrostis Stolonifera(As) on the other hand has decreased slightly which is from T0: 1338.21 ug/gFW to T16: 892.01 ug/gFW.
Figure 7. Chlorophyll a alteration.
Chlorophyll b :
For the chlorophyll b content Ps also showed the significant decrease of amount, from T0: 643.12 ug/gFW to T16: 255.98 ug/gFW. (Figure 8)
Lp has decreased from T0:435.40 ug/gFW to T16: 326.00 ug/gFW, at T2 there was a slight increasment 472.17 ug/gFW.
Pp has decreased from T0:660.27 ug/gFW to T16: 404.83 ug/gFW. Fa has decreased from T0:678.54 ug/gFW to T16: 435.91 ug/gFW.
As has decreased slightly which is from T0: 629.72 ug/gFW to T16: 455.18 ug/gFW.
Carotenoids:
For the Carotenoids content Ps has decreased from T0: 345.63 ug/gFW to T16: 114.93 ug/gFW. (Figure 9)
Lp has decreased from T0:238.38 ug/gFW to T16: 127.19 ug/gFW. Fa has decreased from T0:384.55 ug/gFW to T16: 134.71 ug/gFW. Pp has decreased from T0:369.08 ug/gFW to T16: 152.48 ug/gFW. As has decreased from T0: 272.22 ug/gFW to T16:184.25 ug/gFW.
Figure 9. Carotenoids alternation.
The results concludes that following the UV-B exposure, total chlorophyll levels decreased gradually in all species. Of the all the selected turfgrasses Poa supina was the most sensitive to UV-B irradiance compared with other turfgrasses and Agrostis stolonifera was more tolerant than other ones which indicated that the chlorophyll and carotenoids contents were affected by UV radiation.
3.2. Results of Biometric experiment Tillers
The species Tall fescue (Fa) and Poa supina (Ps) recorded values that did not differ statistically and did not follow a particular trend in relation to the exposure period to UVB.
Perennial ryegrass recorded values that differ statistically in relation to exposure period. In particular the higher value was recorded at 14 days of exposition to UVB
(8,2 tillers cm-2). With 16 days of exposition we can observe an abrupt reduction of
values (3,4 tillers cm-2).
Kentuky bluegrass (Pp) showed a fluctuating trend of the number of tillers relating to
exposition to UVB with the higher value at T10 (9,1 tillers cm-2) and the lower value
at T14 (4,1 tillers cm-2).
Agrostis stolonifera (As) increased significantly the number of tillers already after four days of exposition to UVB, anyway even with more prolonged exposures the values remained high.
Leaf width, leaf length and leaf surface
No statistical difference in leaf width was observed for Fa, Lp and Pp as affect of UVB exposition.
Ps registered the higher value of leaf width in correspondence of 12 days of exposition (2,5 mm).
As at 14 and 16 days of exposition (2,5 mm).
As observed for leaf width no statistical significant difference in leaf length was observed for Fa and Lp as effect of UVB exposition.
Pp registered the lower value of leaf length at the T8 (46mm) exposition.
Ps recorded some fluctuation of values with the lower value at T16 (25mm) and the higher at T12 (36mm).
As shows a clear reduction of leaf length with the increase of exposition to UVB rays, the reduction is already noticeable in the plants exposed for 6 days, with values ranging from 36 to 41mm.
No statistical difference in one leaf surface was observed for Fa and Lp as effect of UVB exposition.
Pp recorded a decrease of leaf surface until the T12 (63 mm2), for the more
prolonged periods of exposure (T14 and T16) the values resulted high (respectively
113 and 114 mm2).
As for leaf width and leaf length, Ps recorded some fluctuation of values of leaf
surface, with the lower value at T0 and T8 (33 mm2) and the higher at T12 (90 mm2).
As recorded the higher values of leaf surface at T14 and T16 (respectively 88 and 90 mm2)
Leaves fresh and dry weight
No statistical difference in leaves fresh weight was observed for Fa and Lp.
Pp recorded some fluctuating values of leaves fresh weight depending on the days of exposition, with the lower values registered at T2, T12, T14 and T16 (from 0,20 to 0,22 g cm-2), and the higher at T6 (0,43 g cm-2).
higher at T8(0,33 g cm-2).
As recorded the lower values of leaves fresh weight at T14 and T16 (0,10 g cm-2) and
the higher at T2 (0,30 g cm-2).
No statistical significant difference in leaves dry weight as affect of UVB exposition was observed for Fa, Lp and Pp.
Ps recorded fluctuating values like for fresh weigh with the lower value of dry weight al T4 (0,03 g cm-2) and the higher value at T8 (0,07 g cm-2).
As recorded the lower value at T16 (0,02 g cm-2) and the higher at T0 and T2 (0,07 g
cm-2).
Plants growth
Plants growth from 20 April (the beginning of the trial and of the exposition to UVB) to 30 May (the end of trial) highlighted some differences between the species.
Fa shows an increased growth with exposure to UVB of 6 and 8 days (2,6 cm), and a stop of growth with the 12 days exposure.
Lp while recording the stop of growth at T14, in general shows a reduction of growth with plants exposed for the longer periods.
Pp recorded the lower values at T10, T12 and T16 (1,8, 1,6 and 1,8 cm respectively). Ps stopped the growth after six days of exposure and not even the time spent in the greenhouse served for recovery.
As progressively reduced growth with the increase of exposition and stopped to growth at T14.
Turf color
Turf color was visually estimated at the end of trial (30 May).
The plants that were not exposed to UVB scored light green color, but in general all species got worse their score as a result of the exposition to UVB.
Fa gradually reduced the color intensity, although the differences with respect of the control were significant only from T6. The minimum score resulted 3 from T12 to T16.
Lp started with a low score even at T0. Values differed statistically from the control starting from T10. The lower score resulted 1,5 al T16.
Pp significantly reduced Color starting from T4.
Ps even after two days showed a deterioration of quality with color scores that gradually reduced up to T16.
As reduced color even after two days with a trend similar to that of Ps.
4. Discussion and Conclusion
Deckmyn and colleagues (1998, 1999) studied the effect of UVB exposition on Lolium perenne and other Poaceae. They observed a slight overall positive effect on biomass production, an increased tillering and a reduced plant height.
In our study, we can observe an increase in tillering in Lp after 14 days of exposition to UVB and in Poa pratensis after 10 days. Agrostis stolonifera increased significantly
tillering starting from 4 days of exposition to UVB. In this case we can assert that the response to UVB radiation of Agrostis stolonifera is in accordance with the previous authors.
With respect to fresh and dry biomass, the species recorded little fluctuations statistically not significant, anyway in general the trend is towards a reduction in values.
With respect to plant growth, obtained by measuring the height, we can observe for Festuca arundinacea an increase with 6 and 8 days of exposition, while for the other species we recorded a reduction as in the case of Lolium perenne and Poa pratensis, in accordance with Deckmyn and collegues, if not a total growth block.
For leaf width, leaf length and leaf surface, only Agrostis stolonifera showed a clear response to UVB radiation.
In the study by Robakowski (1999), the high level of UV-B radiation reduced chlorophyll content by 20% in comparison to the control. On the other hand, in the study by Shorska(2000) effect of the high UV-B radiation reduced chlorophyll content to 50% of the control. In our study we can observe that there are decrease in the chlorophyll and carotenoids content, especially the Poa supina had the noticeable decrease on chlorophyll, carotenoids content(table 12,13,14), for example Poa
supina even stopped the growth at 6th day of radiation treatment. The decrease of
the pigments content followed by Fastuca arundinacea, Poa pratensis, Agrostis stolonifera. The Lolium perenne had the least decrease respect to the other species. Turfgrass species did not have very unique response to the UV-B radiation but they
do have some influences by the radiation. In some case the UVB influence on the studied parameters is clear, as the above-mentioned case of tillering in Agrostis stolonifera, pigment content in Poa supina. In other further studies by increasing the intensity of UV-B radiation, the exposure time or choosing the different types of turfgrasses might have a noticeable response to the radiation.
Table 4. N° TILLERS cm-2 measured at the end of trial (30 May) with T0= no exposition to UVB,
T16=16 days of exposition to UVB
Fa Lp Pp Ps As T0 3,7 5,0 8,1 5,6 5,1 T2 3,9 5,0 8,6 6,0 5,6 T4 3,7 5,1 6,4 6,3 9,6 T6 3,7 5,4 6,4 5,9 9,1 T8 3,0 5,9 8,3 5,4 9,0 T10 3,3 5,4 9,1 4,3 8,3 T12 3,9 7,6 7,6 6,3 9,1 T14 4,0 8,2 4,1 6,3 8,4 T16 3,3 3,4 7,0 5,0 9,3 DMS 0.05 ns 3,1 3,7 ns 2,2
Table 5. Leaf width (mm) measured at the end of trial
Fa Lp Pp Ps As T0 2,3 1,1 1,1 1,1 1,1 T2 2,1 1,0 1,5 2,0 1,0 T4 2,4 1,0 1,0 2,2 1,0 T6 2,3 1,2 1,0 1,6 1,0 T8 2,5 1,6 1,0 1,0 1,0 T10 2,4 1,7 1,0 2,1 1,0 T12 2,6 1,0 1,0 2,5 1,0 T14 2,0 1,2 1,7 1,5 2,5 T16 2,0 1,2 1,7 1,5 2,5 DMS 0.05 ns ns ns 1,2 1,3
Table 6. Leaf length (mm) measured at the end of trial Fa Lp Pp Ps As T0 65 66 73 30 53 T2 63 69 66 33 50 T4 71 58 63 35 48 T6 79 64 67 30 41 T8 69 54 46 33 42 T10 62 68 64 29 38 T12 66 64 63 36 34 T14 70 58 68 30 35 T16 73 67 68 25 36 DMS 0.05 ns ns 18 8 12
Table 7. One leaf mean surface (mm2) measured at the end of trial
Fa Lp Pp Ps As T0 147 72 80 33 58 T2 133 69 99 66 50 T4 168 58 63 77 48 T6 183 74 67 49 41 T8 172 86 46 33 42 T10 148 113 64 61 38 T12 169 64 63 90 34 T14 140 68 113 45 88 T16 146 79 114 38 90 DMS 0.05 ns ns 25 34 28
Table 8. Leaves fresh weight (g cm-2) measured at the end of trial
Fa Lp Pp Ps As T0 0,21 0,21 0,31 0,32 0,24 T2 0,24 0,17 0,20 0,24 0,30 T4 0,19 0,26 0,31 0,13 0,18 T6 0,20 0,23 0,43 0,24 0,16 T8 0,20 0,26 0,30 0,33 0,24 T10 0,20 0,18 0,32 0,23 0,21 T12 0,15 0,29 0,20 0,26 0,25 T14 0,17 0,23 0,22 0,22 0,10 T16 0,17 0,23 0,22 0,22 0,10
DMS 0.05 ns ns 0,16 0,10 0,11
Table 9. Leaves dry weight (g cm-2) measured at the end of trial
Fa Lp Pp Ps As T0 0,06 0,06 0,05 0,07 0,07 T2 0,06 0,05 0,05 0,06 0,07 T4 0,05 0,07 0,08 0,03 0,04 T6 0,05 0,07 0,07 0,05 0,05 T8 0,05 0,06 0,04 0,07 0,05 T10 0,05 0,04 0,05 0,04 0,05 T12 0,04 0,05 0,05 0,05 0,05 T14 0,05 0,05 0,05 0,05 0,05 T16 0,06 0,07 0,06 0,05 0,02 DMS 0.05 ns ns ns 0,02 0,03
Table 10. Plants Growth (cm) from 20 April to 30 May with T0= no exposition to UVB, T16=16 days of exposition to UVB Fa Lp Pp Ps As T0 1,6 4,8 4,7 0,2 3,0 T2 1,8 3,8 3,2 0 2,0 T4 2,0 3,8 3,5 0,4 2,0 T6 2,6 4,4 3,6 0 1,4 T8 2,6 4,4 3,6 0 1,4 T10 0,8 3,4 1,8 0 0,4 T12 0 1,6 1,6 0 0 T14 1,8 0 3,6 0 0 T16 1,6 2,8 1,8 0 0 DMS 0.05 0,6 1,0 0,8 ns 0,8
Table 11. Turf Color (1-9: 1 light green ; 9 dark green) measured at the end of trial.
Fa Lp Pp Ps As T0 6,0 3,5 5,0 5,0 4,0 T2 5,0 3,0 4,0 3,0 3,0 T4 5,0 3,3 3,0 2,5 3,0 T6 3,5 3,0 3,0 3,0 2,5 T8 3,5 3,5 3,5 2,5 2,5 T10 4,0 2,5 2,5 2,5 2,5 T12 3,0 2,0 1,5 1,5 1,5
T14 3,0 2,0 2,0 1,5 1,5
T16 3,0 1,5 1,5 1,5 1,5
DMS 0.05 1,5 1,0 1,5 1,5 1,0
Table 12. Chlorophyll a content.
As Fa Ps Pp Lp
0 1338.212204 1601.890533 1545.301533 1507.6936 996.657126
2 1024.332933 1269.289667 1356.2738 1353.331467 1025.776467
8 867.6868 967.2371333 642.6148 943.7920667 924.5658
16 892.0127333 845.1473333 490.1818667 828.9400667 534.323
Table 13. Chlorophyll b content.
As Fa Ps Pp Lp
0 629.7210801 678.5466667 643.1246667 660.2733333 435.4068522
2 483.892 569.1593333 603.7233333 600.2026667 472.1726667
8 453.924 480.9513333 313.0573333 462.7806667 462.1073333
16 455.186 435.9186667 255.98 404.8366667 326.0073333
Table 14. Carotenoids content.
As Fa Ps Pp Lp
0 272.2223882 384.551456 345.635145 369.0886811 238.3851872 2 215.2957048 277.3398971 294.1566863 302.0591213 221.8634682 8 190.2770617 158.4637006 152.6648481 204.4277079 169.7083742 16 184.2590393 134.7139401 114.9382966 152.4854327 127.1905151
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