5. Genus Amaryllis L.
5.1 Generalities
Description
The genus Amaryllis L. contains glabrous, bulbous, scapose (rarely more or less acaulescent), perennial herbs (Tutin et al., 1980). The leaves are all basal, linear to lorate or oblanceolate, often distichous. The flowers are in an umbel of 4-8 (-12) hermaphrodite flowers, subtended by a spathe 2-valved; each flower is subtended by a linear bracteole. The flowers are campanulate, bright pink, fragrant, inclined or somewhat nodding, usually slighty zygomorphic. The perianth is formed by six petaloid segments, arising from an hypanthial tube; the corona is absent. The stamens are six and they are formed by filaments much longer the anthers. The ovary is inferior and 3-locular; the stigma is capitate or shortly 3-lobed. The fruit is a subglobose, dehishing irregularly capsule, with a mericarp somewhat fleshy. The seeds are rather few.
Likewise in other genera of Amaryllidaceae, some morphological adaptations to xeric habitats are present in the leaves, even if most of the aerial part of the plants dies back during the dry season.
Systematic frame and distribution
According to Dahlgren (1985) the genus Amaryllis L. is included in the tribus
Amaryllidae of the family Amaryllidaceae, which are placed, togheter with
Alliaceae, Hyacinthaceae, and other families, in the order Asparagales. The order
Asparagales is included in the superorder Liliiflorae of the Monocotyledons.
In the context of the family Amaryllidaceae, there have been a long nomenclatural controversy over the generic delimitation of Amaryllis L. and the allied genus
Hippeastrum Herb. The two genera have different areas of distribution and for over a century, before the pubblication of Upholf (1938), the South American species have been placed in Hippeastrum while the name Amaryllis belladonna, upon which the Linnean genus Amaryllis is now based, has been applied to the South African species commonly known as “Cape belladonna” (Moore, 1963).
The two genera are similar in general vegetative and floral morphology, but they have important differences in the internal anatomy of leaves, bulbs, and roots, as affirmed by Arroyo (1981). She indicated also a similar karyotype complement, while Naranjo (1987) pointed out some significant karyological differences between the two genera.
An accepted proposal by Goldblatt (1984) to conserve distinct generic names of
Amaryllis for the South African and Hippeastrum for the South American species estabilished their separate identity.
Brandham and Bhandol (1997) although observed remarkable karyotypic uniformity between the two genera, confirmed their distinction, since there are many cases in which the same karyotype occurs in group of genera that are clearly related, but remain distinct on morphological and genetical ground.
At present numerous species of both the two genera are coltivated as decorative bulbous plants in many countries, from where they often escaped from cultivations becoming naturalized. Consequently their actual area of distribution is wider in respect to the original tropical and subtropical territories of Africa and America respectively, and they can be found normally also in the flora of temperate countries likewise Europe.
5.2 Amaryllis belladonna L.
5.2.1 Generality
According to some authors (Dahlgren, 1985; Goldblatt, 1984)
Amaryllis belladonna is the only member of the genus Amaryllis, and it has a natural distribution restricted to the south-western Cape region of south Africa, even if it is a widely cultivated ornamental.
In times past several authors referred to Amaryllis belladonna many species from intertropical region of America, Africa and
Asia; the valuable importance of this and allied species in horticulture, also for the strong hybridization occurred, contributed to originate the nomenclatural controversy over mentioned, attributing to Amaryllis belladonna many species of different
Amaryllidaceae genera, especially of the genus Hippeastrum (Gerola, 1962).
Also the karyology of Amaryllis belladonna has given conflicting results among many authors (Sato, 1938; Gouws, 1949; Flory et al., 1976; Arroyo, 1981 etc.), and it could be due, in part, to the fact that some of these studies were done on material of unknown origin. This disagreement has decreased the value of existing data for the evolutionary and taxonomic purposes.
Anyway several authors confirmed for Amaryllis belladonna the basic chromosome number x=11, as in other species of the allied Hippeastrum.
Diploid populations with 2n=22 has been indicated by many authors (Gouws, 1949; Larsen, 1960; Arroyo, 1981) basing their studies on material from south Africa or Gran Canaria.
Additionally, a frequency of 50 % of tetraploid populations has been indicated by Brandham and Bhandol (1997) in their studies on many populations from Bolivia, probably escaped from cultivation. It is nevertheless possible that the tetraploids are not so common in the wild; the apparently high frequency could be a reflection of their preferential field collection, being the tetraploids (and in general the polyploids) larger and more showy than the diploids in many genera, e.g. Narcissus (Brandham, 1986). Odd number polyploids (3x, 5x, 7x) have been recorded frequently (Arroyo, 1982), but because they are sterile they will not be expected to occur widely in the wild, except in the case of large vegetative spreading. Indeed odd polyploids of the allied genus Hippeastrum were found among garden-grown plants by Khoshoo (1979) and Arroyo (1981), while they were not recorded among wild plants by Naranjo and Andrada (1975). Only in species with highly developed vegetative propagation mechanisms or apomictic seed production can odd number polyploids compete successfully with diploids and other polyploids.
The karyotype resulted uniforme and bimodal, with seven long acrocentric and four smaller metacentric chromosomes in the basic set, according to Brandham and Bhandol (1997). They didn’t observe secondary constriction or associated satellites. The total chromosome lenght of the diploid set resulted 144 µm.
An identical karyotype has reported by Arrojo (1981) for native plants, pointing out the similarity with the chromosomic complement of several species of
Hippeastrum investigated.
A quite different karyotype has given by Naranjo and Poggio (1987) for material from south Africa; they indicated six submetacentric, one metacentric-submetacentric and four metacentric chromosomes in the basic complement. The metacentric-submetacentric pair was indicated to have a large satellite on the short arm.
5.2.2 Results
10 µm
2n = 2x = 22: 8 sm + 2 st-SAT + 4 sm + 8 m
Fig. 22. Amaryllis belladonna L., K510: microphotograph of a somatic metaphasic
5.2.3 Discussion
The present investigation has allowed to determinate the chromosome number 2n=22 for a population of Amaryllis belladonna L. from Zakynthos, Ionian Islands.
Differently from the other species here studied, the taxon in object isn’t spontaneous in the place of picking as natural component of the Greek flora. In particular, Amaryllis belladonna is in Greece, likewise in other temperate countries, an introduced plant, cultivated as ornamental and naturalized; in this way it can reproduce by own means. Also in the island of Zakynthos it may originally escaped from the garden culture and subsequently it may began to reproduce in the wild.
The basic chromosome number here found, x=11, is in agreement with several authors previously mentioned. Moreover, the diploidy of this karyotype confirms the results on most of the wild plants investigated by other authors, both from the native country and the others in which the species is fully naturalized.
The population studied was found in an olive grove, that is the predominant component of the landscape of Zakynthos. Often olive trees are left from the cultures originating sub-wild olive woods below which wild herbaceous plants can grow; this may be the case of the population investigated, which probably was reproducing there by normal sexual means.
In this frame the diploid karyotype obtained can support the observation that wild populations show mostly the diploid set, while cultivated populations, spreading in the field only by vegetative means, give often rise to high poliploidy level, in particular odd poliploidy in the case of highly developed reproductive systems, as over mentioned.
Concerning the karyotype morphology, the idiogrammatic formula obtained is:
2n = 2x = 22: 8 sm + 2 st-SAT + 4 sm + 8 m
It is symmetrical, with chromosomes of more or less the same size, except for the last four metacentric chromosome pairs which are quite smaller than the others. With regard to the latter chromosomes, the present investigation agrees with Brandham and Bhandol (1997) and Arrojo (1981), but concerning the other chromosomes they reported seven long acrocentric pairs, while in the present study six submetacentric
and one subtelocentric pairs are present. Furthermore they didn’t observe any associated satellites, while here two well visible large satellites can be seen on the short arm in both of the chromosomes of the fifth (subtelocentric) pair.
The karyotype obtained is nevertheless in perfect agreement with Naranjo and Poggio (1987), in their investigation on south African plants, both for the chromosome morphology and for the large satellites present.
