| Amphicarpaea edgeworthii Benth. belongs to the tribe Phaseoleae of Papilionoideae, Leguminosae. The species can produce aerial chasmogamous flowers, aerial cleistogamous flowers, and subterranean cleistogamous flowers in the same individual which develope into aerial and subterranean fruits, respectively. Therefore, it is a typical amphicarpous species. Glycine soja Sieb. et Zucc. is a legume species, too. However, G. soja is an aerocarpous species for it only has aerial chasmogamous flowers and fruit. To study the adaptability of amphicarpy to ecological environment, seed biology, photosynthetic characteristics, dynamic changes of matter and energy, anatomy of vegetative organs, and reproductive biology of the two legume species were compared in the present research. The main results were concluded as follow:(1) Aerial fruit and seeds of A. edgeworthii are greatly different from subterranean ones. The aerial fruit is a long circle pea which was21.74mm long and5.69mm wide, containing two to three seeds, while the subterranean fruit is a oval membranous pea that7.83mm long and6.72mm wide, containing one to two seeds. The size of aerial seed is about10times bigger than that of subterranean one. The shape of fruit and seeds in G. soja were similar to those in A. edgeworthii. Time course for water absorption and dehydration of seeds and the seeds germination rate showed that both the subterranean seeds of A. edgeworthii and G. soja have hard seed coat as their germination rate under suitable condition is about43.33%and4.44%, respectively. However, the subterranean seed had high germination rate for they didn’t have hard seed coat. Therefore, the co-exit of the aerial and subterranean seeds and their different germination characteristics reduced the competition among siblings of A. edgeworthii, which was ecologically significant for the population to adapt to the unstable habitat. Anatomy of pericarp and seed’s coat suggested that the structure of seed coat partially caused seed coat of A.edgeworthii’s aerial seeds and G. soja’s seeds’hard. Therefore, change the structure of seed coat is important to removal of hard seed coat. The results of removal of hard seed coat by concentrated sulfuric acid and cold stratification showed that aerial seeds of A. edgeworthii would have high germination rate after treatment with concentrated sulfuric acid for about20minutes, while seeds of G. soja needed about45minutes. Both of the two kinds of seed would increase in their germination rate through80days’cold stratification.(2) Diurnal change curve of net photo synthetic rate, chlorophyll fluorescence parameters, chlorophyll content and specific leaf weight (SLW), etc, showed that G. soja had higher photosynthetic capacity than the A. edgeworthii. However, the difference between them constantly decreased as growth processed. When it came to the period of fructescence, the photosynthetic capacity of the two legume species was closed to each other. Results of differential thermal analysis, ratio of dry weight to fresh rate, nitrogen content and organic carbon content showed that matter and energy was prior to be accumulated in the underground part of A. edgeworthii and it is to be gradually transferred to the aboveground part. G. soja had the opposite process. In this experiment, resources were limited as A. edgeworthii and G. soja grown in the same flowerpot. In this case, A. edgeworthii accumulated the resources preferentially in the underground part for reproduction. And then, the aboveground part began to grow and produce higher quality seeds if the environment improved.(3) Anatomy of the vegetative organs of A. edgeworthii and G. soja suggested that G. soja had developed conducting tissue to adapt to the drought environment, while A. edgeworthii had roots and zhizome which could store nutrient to ensure the survival of plants in the drought environment. In addition, G. soja had well developed palisade tissue and vein, which made its leaf resist high light irradiance, while A. edgeworthii’ leaf was thin and the palisade tissue was relatively underdeveloped, with a small amount of chloroplast in the epidermal cells, which made it more shade-tolerant. Thus, anatomical structures of A. edgeworthii and G. soja adapted to the adverse environment were different. Furthermore, A. edgeworthii had zhizome to guarantee the existence of subterranean propagules in adverse environments.(4) Aerial flower of A. edgeworthii and flower of G. soja were typical papilionaceous which had vivid color in petal and could secrete nectar; the values of P/O were2584.29±314.39and2234.05±634.52, respectively; fruit setting rate of cross pollination were61.11%and4.17%, respectively. All the results illustrated that both of the two had the ability to reproduce by cross pollination. However, the overlap of two phases, pollen had relatively high germination rate and stigma could receive the pollen grains, and the similar fruit setting rate of natural pollination and self pollination suggested that self pollination was the main pollination method in the two kinds of flowers. Subterranean flower of A. edgeworthii was facultative self pollination as its P/O value of was143.44±53.24. Therefore, A. edgeworthii were highly likely to self-pollinate. This mating strategy could ensure the fertilization of ovule. |
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