Effect of Ovule Position in the Pod on Patterns of Seed Formation in Two Species of Lathyrus (Leguminosae: Papilionoideae)

Abstract

Using a combination of observations of fate of ovules in matured fruits and of fluorescence techniques to study pollen tube growth and fertilization of ovules, we examined patterns of seed formation within pods in natural populations of two species of Lathyrus, L. sylvestris and L. latifolius. We also examined variation in these patterns within and among populations and between two consecutive years. In both species, only a portion of the ovules were fertilized. Fertilization occurs over a period of several days and ovules at the stigmatic end of the fruit are the first to be fertilized. Fertilized ovules farthest from the stigma are closest to the maternal nutrition. The pattern of embryo abortion is interpreted as a balance between the early start and genetic quality of embryos near the stigma, on the one hand, and the nutritional advantage of proximity to maternal nutrients, on the other. Differences between the two species in patterns of seed maturation are postulated to be related to differences in breeding system. In L. sylvestris, a higher frequency of selling leads to less genetic diversity of pollen deposited on the stigma, lower competition among potential sires, and a more nearly random pattern of ovule fertilization and maturation within the pod.

Components of fecundity and abortion in a tropical tree, Dahlstedtia pentaphylla (Leguminosae)

“…If basal ovules have a spatial advantage (Horovitz et al, 1976;Heering, 1994) the stigmatic ovules could have a similar advantage of being the first to be fertilized and establish a stronger resource sink. Such strong resource sink in first fertilized ovule at the stigmatic end leading to a high frequency of pods with stigmatic seeds has been shown in many different species (Lee and Bazzaz, 1982, Hossaert and Valéro, 1988, Arathi et al, 1999). These arguments were tested in the present study in the neotropical legume species Dahlstedtia pentaphylla (Taub.)…”

“…Some ovules do not develop due to the lack of fertilization and for those that are fertilized, embryos may be aborted during embryogenesis (Sedgley, 1980;Bawa and Webb, 1984). The occurrence of abortion is not exclusive of the legumes, but this family offers convenient opportunities for abortion studies because of the linear arrangement of ovules within the ovary, which permits the study of gradients of seed formation within fruits (Hossaert and Valéro, 1988). Several factors can lead to flower and fruit abortion (Lloyd, 1980;Stephenson, 1981;Bawa and Webb, 1984).…”

“…Among these are quantity of pollen grains deposited on the stigmas (Mogensen, 1975) and ovule competition for the resources required for seed development (Lloyd, 1980). Such competition combined with resource limitation, could lead to the selective abortion of ovules and seeds (Hossaert and Valéro, 1988). Abortion of embryos that occur farthest from the stigma is the most common pattern found in legumes (Bawa and Buckley, 1989).…”

Protogynous, pollen limitation and low seed production reasoned for the dieback of Spartina anglica in coastal China

“…Abortion of flowers and fruits could occur at various stages of development. Factors affecting seed formation acted both before and after fertilization and could be determined by analyzing the characteristics of ovules in the fruits that attain maturity [14]. The important factors that acted in the pre-fertilization were the limitation of pollen grains [15], self-incompatibility and gametic sterility [16].…”

Structural aspects of ovule and seed development and nonrandom abortion inMelilotus officinalis (Fabaceae)

“…Although eight ovules form in an apocarpous, unilocular gynoecium, the number of maturing ovules is reduced after fertilization to one (rarely to two), by abortion (Wiens 1984, Wiens et al 1987. The abortion of developing seeds in different species may occur randomly or nonrandomly with respect to ovule position within an ovary (Horovitz et al 1976, Hossaert andValero 1988). A study (Schouten 1998) of the effect of ovule position on seed formation in different populations of M. officinalis has shown that seed set occurs predominantly in the basal ovule position, is very low in the second ovule position from the base, and is extremely rare in the upper ovule positions.…”