SEASONAL-CHANGES IN THE INCIDENCE OF APOMIXIS OF DIPLOID, TRIPLOID, AND TETRAPLOID PLANTS OF PASPALUM-CROMYORRHIZON
SEASONAL-CHANGES IN THE INCIDENCE OF APOMIXIS OF DIPLOID, TRIPLOID, AND TETRAPLOID PLANTS OF PASPALUM-CROMYORRHIZON
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DOI：
10.1007/bf00021860
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发表时间：
1986-06-01
期刊：
影响因子：
1.9
通讯作者：
QUARIN, CL
中科院分区：
文献类型：
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作者：
QUARIN, CL
在开花期的不同时间间隔，在一个高度有性二倍体细胞型的雀稗TRIN.中测定了无融合生殖发生率的变化，同一种的天然四倍体细胞型，以及通过用四倍体的花粉授粉2x细胞型产生的三倍体和四倍体种内杂种。生殖行为是通过观察成熟胚珠中的胚囊来确定的。本种配子体无融合生殖的特征是无孢子胚囊，其数量、在胚珠内的方向、尺寸和形状与正常胚囊不同，并且没有反足细胞。无融合生殖的可能性随着倍性水平的增加而增加，表明无融合生殖的发生率存在基因剂量效应。在三个倍性水平中，当植株达到最大花头数时，无融合生殖的发生率最高。这些发现表明，同样的环境条件，有利于开花也应该是responsbile无融合生殖的发病率增加。在受控条件下的另一个实验表明，光照条件应该是控制无融合生殖量的因素之一。因此，多倍体和无融合生殖在该禾本科植物的扩散和进化中具有特殊的意义。4x兼性无融合生殖细胞型在自然界中比高度有性的2x更常见。此外，在开花季节产生的大多数种子应该是无性繁殖的。因此，无融合生殖迅速增加了携带成功的母本基因型的植物的数量，并且有性生殖在不利的环境条件下变得重要。
Changes in incidence of apomixis were determined at different intervals of the flowering period in a highly sexual diploid cytotoype of Paspalum cromyorrhizon TRIN., a natural tetraploid cytotype of the same species, and in the triploid and tetraploid intraspecific hybrids that were produced by pollinating the 2x cytotype with pollen of the tetraploid. Reproductive behaviour was determined from observations of embryo sacs in mature ovules. Gametophytic apomixis in this species in characterized by aposporous embryo sacs which differ from normal sacs by their number, orientation inside the ovule, their dimensions and shape, and the absence of antipodal cells. The potential for apomictic reprodution increased in relation to the ploidy level, suggesting a gene dosage effect in the incidence of apomixis. In the three ploidy levels, the highest incidence of apomixis was observed when the plants reached the maximum number of flowering heads. These findings suggest that the same environmental conditions that favour flowering should also be responsbile for increasing the incidence of apomixis. An additional experiment under controlled conditions indicated that the light regime should be one of the factors that govern the amount of apomictic reproduction. Thus, polyploidy and apomixis should be of special significance in the dispersion and evolution of this grass species. The 4x facultative apomictic cytotype is far more frequent in nature than the highly sexual 2x. Moreover, most of the seeds produced in a flowering season should arise asexually. So, apomixis rapidly increases the number of plants bearing the successful maternal genotype, and sexual reproduction becomes important in adverse environmental conditions.