小麦果皮绿色层中^(14)C标记同化物在胚珠内的分配与定位

Distribution and Localization of ^(14)C-labelled Assimilates of Pericarp Green Layer Within the Ovule of Wheat Caryopsis

小麦离体颖果饲喂~14CO_2后,经冷冻取代,于膜显微放射性自显影,追踪与检查了包括可溶性糖在内的~14C标记同化物在胚珠内的分配与定位。颖果绿色层细胞的高光合效率不仅保证了同化物的即时输出,而且还可以淀粉形式暂贮在叶绿体内。绿色层光合产物主要向腹沟处汇集,通过该处的维管束与珠心突起向胚乳方向迁移。~14C标记同化物以逆浓差梯度方式从珠心向珠心—胚乳交界处质外体空间输出并在胚乳内呈不均匀分布和富集于原胚端活跃增殖生长的区段内。绿色层同化物以多种方式进入原胚,主要以可溶态形式存在。同化物可能通过珠孔直接就近为原胚吸收。

After ^(14)CO_2 was fed to the detachedwheat caryopsis, the distribution and locali-zation of labelled assimilates (including wa-ter-soluble compounds) within the ovules weretraced and examined with freeze-substitutionand dry microautoradiography. The highphotosynthetic rate of green layer cells of pe-ricarp could produce more assimilates thancould be exported, and thus there was tem-poral storage of them in a form of starch inchloroplasts. The assimilates of green layerwere massively transported to the creaseregion, and moved to the inner ovule throughnucellar projection. The labelled assimilateswere exported from the nucellus to the apo-plast of nucellus-endosperm boundary againstthe concentration gradients. The nutrientsentered the endosperm and were unevenlydistributed in it. Most of them were con-centrated in the actively proliferating regionnear proembryo. The transported assimila-tes moved into proembryo by multiple path-ways and existed in it mainly in solubleform. The possibility of the direct absorptionof the assimilates by proembryo through mi-cropyle is discussed.