小麦颖果果皮绿色层内同化物的合成与分配

小麦幼嫩颖果中,果皮内侧发育出由内表皮与亚表皮组成的一薄层绿色组织。显微与亚显微结构观察表明,虽绿色层只接受到自然光照的1/4～1/8,叶绿体仍能正常发育,叶绿素含量与叶绿体数量均高出旗叶。大量胞间连丝联接相邻的绿色细胞,并在一定时期形成开放的胞间通道,显然有利于同化物的快速胞间运输。离体颖果饲喂~14CO_2试验证明,新合成的同化物从绿色细胞输向胚珠。绿色层产生的同化物可能通过合点端的珠心进入胚乳或通过珠孔直接汇聚到胚珠和分化中的原胚。

Synthesis and Distribution of Assimilates in the Green Layer of Pericarp in Developing Wheat Caryopsis

A layer of green tissue composed of inner epidermis and subepidermis of pericarp develops along with the growth of wheat caryopsis, while the endosperm is growing rapidly and proem- bryo is differentiating. By observation under light microscope and electron microscope, mea- surement of photosynthesis and feeding and tracing of isotope ~(14)CO_2, it shows that although the green layer receives only 1/4 --1/8 of natural light, it develops chloroplasts normally, which have higher chlorophyll content and higher ef ficiency of photosynthesis than those of flag leaf. The adjacent green cells are connected by nu- merous plasmadesmata, which form an opened and enlarged intercellular canal at proper stage. This canal evidently favours the rapid intercel- lular transport of assimilates. After feeding ~(14)CO_2 to isolated caryopsis, green tissue contains many labelled photosynthates, and the radio- activity in grcen tissue gradually decrease; while that in ovule increases. So it is confirmed that the newly-synthesized assimilates transport from green cells to ovule. The assimilatcs produced by green cells may travel first through the nucel- lus of chalazal region into the developing en- dosperm, and may, also, migrate through mic- ropyle directly into the ovule and differentiating proembyo.