种植密度对玉米种皮形态建成及胚乳淀粉粒发育的影响

Effect of Planting Densities on Morphogenesis of Seed Capsule and Development of Starch Granule in Maize Endosperm

【目的】阐明种植密度对玉米种皮形态建成及胚乳淀粉粒发育的影响。【方法】利用荧光显微镜和透射电镜,研究了30000株/公顷(低密度)和90000株/公顷(高密度)两种种植密度下玉米种皮形态建成及胚乳淀粉粒发育规律。【结果】随着籽粒的发育,内珠被中的细胞质首先作为营养物质被吸收、解体,形成珠被绒毡层;珠被绒毡层退化消失的同时,子房壁细胞也离散解体,最终使子房壁和内珠被愈合在一起,形成种皮。胚乳内淀粉粒的积累是由内向外进行的,胚乳第二层细胞内淀粉粒的发育要早于胚乳最外层细胞。授粉后10～15d是胚乳淀粉粒发育的质变关键时期(由无到有);而授粉后20～25d是淀粉粒发育的量变关键时期(由少到多)。高密度处理的种皮细胞总层数约占低密度处理的1/2,但其各层细胞中的内容物相对较多,种皮形态建成的速度较慢。授粉后10～20d,高密度处理的胚乳淀粉粒明显比低密度处理大且多;而授粉后25d表现相反。玉米胚乳淀粉粒的剖面面积多数集中在0～0.8μm2之间,约占52.90%,大于3.6μm2的仅占0.72%,有90.58%的淀粉粒的剖面面积小于2.0μm2。【结论】通过改变玉米种植密度,可以调节其种皮形态建成及胚乳淀粉粒发育速度。

[ Objective ] The objective of the experiment was to elucidate the effect of planting densities on morphogenesis of seed capsule and development of starch granule in maize endosperm. [Method] Fluorescence microscope and transmission microscope were used to study the morphogenesis of seed coat and development of starch granule in maize endosperm in two planting densities, 30 000 plants/ha （low density） and 90 000 plants/ha （high density）. [Result] The results showed that the cytoplasm of inner-integument were absorbed and crushed firstly to develop into integumentary tapetum. Companied with the degenerateness of integumentary tapetum, the ovary wall cells dispersed and with the result that the ovary wall united with the inner-integument, referred to as seed capsule. The starch was accumulated from the inside to outside of the maize endosperm. The phase, from 10 to 15 days after pollination, was decisive for the qualitative changing of starch granule development but from 20 to 25 days after pollination was the critical phase of quantitative changing of that. The cell contents under high density were more abundant and the morphogenesis speeds of seed capsule were slower than those under low density. From 10 to 20 days after pollination, the starch granules under high density were obviously larger and more than those under low density but which was smaller and less at 25 days after pollination. Most of the starch granule section area ranged from 0 to 0.8μm^2, which account for 52.90% of total starch granule. Only 0.72% of total starch granules that section area was higher than 3.6μm^2. [Conclusion] The results suggest that the speeds of seed capsule morphogenesis and starch granule development in maize could be regulated by changing the planting densities.