水稻果皮的结构与功能

The Structure and Function of Pericarp in Rice

采用透射电镜观察果皮细胞的超微结构、分光光度计法测定果皮浸提液的吸收光谱和叶绿素含量、氧电极法测定果皮的光合放氧速率、抗体免疫电泳法定量果皮中 Rubisco等方法 ,研究水稻果皮的发育过程、显微和超微结构以及生理功能 ,得到以下主要结果 :上表皮上没有气孔 ;中层细胞富含质体 ,通常外侧中层细胞内的质体为淀粉体 ,而靠近内侧的中层细胞 (含横细胞 )内的质体大多为叶绿体 ,叶绿体呈橄榄状 ,片层结构发达 ;果皮中色素的吸收光谱与叶片的叶绿素相似 ,即在蓝光区和红光区各有一个吸收峰 ,吸收峰分别在 4 4 0 nm和 6 6 0 nm处 ;花后 5 d、 10 d和 15 d的果皮中叶绿素含量分别为 2 .12 μg Chl/个颖果、 2 .4 8μg Chl/个颖果和 1.4 2 μg Chl/个颖果 ;果皮中存在着碳同化的关键酶 Rubisco,花后第 10 d时果皮中 Rubisco的含量最高 ;果皮在呈绿色时具有光合放氧的功能 ,但净光合速率比呼吸速率低 ,并有较长的光合滞后期 ;由于颖果表皮上无气孔 ,推测其进行光合作用所需的 CO2 来自颖果的呼吸作用 ;果皮的发育和扩展情况影响着胚乳的发育和米的形态建成。

The development, the microstructure and super microstructure, and the physiological function of rice caryopsis pericarp were investigated by means of observing the super microstructure under the transmission electron microscope (TEM), measuring the absorption spectrum of extraction solution and chlorophyll content with spectrophotometer, calculating the oxygen evolving rate of photosynthesis with oxygen electrode, assaying the Rubisco with antibody immuno electrophoresis of pericarp. Here are the main results: There′s no stoma on the upper epidermis and there are bounds of plastids in the middle layer cells, under normal condition, the plastids locating in the outer side of middle layer cells are amyloplasts, while most of them in the inner side are chloroplasts that take on the olive shape and have the developed lamellae structure; The absorption spectrum of pigment in pericarp is similar to that of chlorophyll in leaf; that is, there is one absorption peak in blue(440 nm) and red (660 nm) regions of spectra; The chlorophyll contents in pericarp, 5d, 10d and 15d after flowering, are 2.12 μg/per caryopsis, 2.48 μg/per caryopsis and 1.42 μg/per caryopsis respectively; There exists the carbon assimilating key enzyme (Rubisco) in the rice pericarp and its content reaches the highest on the 10 th day after flowering; Although the pericarp had the photosynthetic oxygen releasing function during the greening stage, its net photosynthetic rate was lower than that of respiration and had a longer lag time. Because of no stoma on the epidermis of pericarp, it was concluded that the CO 2 needed in photosynthesis came from the respiration of caryopsis; Moreover, the development and extension of pericarp have influence on the endosperm development and rice grain photomorphogenesis.