水稻灌浆结实期籽粒接受^(14)C-同化产物能力的研究

STUDY ON GRAIN CAPACITY OF^(14)C-PHOTOSYNTHATES DURING GRAIN-FILLING PERIOD IN RICE

在盆栽条件下,以粳稻日本晴为材料,于抽穗后5、20、35d整株标记14CO2 1.5h,同化后24h取样,测定根、叶片、茎鞘、穗轴、枝梗、小枝梗及籽粒中14C同化产物的淀粉量和可溶性糖含量。结果表明:随着抽穗后天数的增加,全株14C同化量明显减少,光合强度下降的幅度大于绿叶重;灌浆初期固定的14C光合产物在同化后24h60%以上被运输到籽粒中,籽粒中14C光合产物的淀粉量和可溶性糖含量均明显高于其他器官,证明灌浆初期籽粒具有主动接受14C光合产物的能力;灌浆后期叶片、茎鞘、穗轴、枝梗、小枝梗中含有大量的14C同化产物,且多为能运输的可溶性糖,但籽粒中14C光合产物很少,说明灌浆后期籽粒接受光合产物能力明显变弱,是造成大量14C光合产物滞留在营养器官中的重要原因;籽粒的含水率和淀粉合成能力与籽粒接受14C光合产物量之间具有明显的伴随关系,推测籽粒的含水率和淀粉合成能力低可能是造成籽粒接受光合产物能力下降的重要原因之一。

Japonica cultivar Nipponbare was used in the pot experiment and the rice plants were fed with14CO2 for 15 h in 5, 20, 35 days, respectively, after heading. Contents of14C\|labeled starch and soluble carbohydrates in organs including root, leaf blade, leaf sheath and stem, panicle axis, branches, pedicel and grain, which were sampled 24 h after assimilation, were analyzed. The results were as follows: As grain grew,14C\|photosynthates decreased obviously and photosynthesis rate decreased more rapidly than the weight of green leaf did. At the beginning of grain filling, more than 60 percent of14C\|photosynthates were translocated into grains 24 h after assimilation and contents of14C\|starch and soluble14C\|carbohydrates in grains were significantly higher than that in other organs, which indicated that grains had the ability of actively accumulating photosynthates. At the end of grain filling, large amount of14C\|photosynthates remained in vegetative organs and most of them were transportable and soluble carbohydrates, however, contents of14C\|photosynthates in grains were very low, which indicated that weak grain capacity might be the cause of accumulation of14C\|photosynthates in vegetative organs. Grain water content and starch synthesis rate were consistent with grain capacity of photosynthates, which implied that low grain water content and starch synthesis rate might be an important cause that led to low grain capacity.