直立穗型粳稻不同粒位籽粒发育的差异

Developmental Differences among Different Positions Grains in Japonica Rice with Erect Panicle Type

以直立大穗型粳稻为试材,经自上而下梯度剪除稻穗枝梗的梯度减库处理,比较稻穗上、中、下部位的1次枝梗(强势粒)和2次枝梗(弱势粒)子粒胚乳细胞发育差别。并以Logistic方程模拟不同粒位子粒的胚乳细胞增殖过程,研究细胞数与粒重在发育过程上的相关性。结果表明:梯度减库后,中下部强势粒总细胞数明显提高,与未减库的对照顶端强势粒水平相近,但下部弱势粒细胞数目始终不及强势粒,与顶端强势粒相差最大;不同穗粒位子粒细胞增殖起始势(R0)呈现上部<中部<下部,强势粒>弱势粒的趋势,而细胞有效增殖期(D)表现为上部>中部>下部,强势粒>弱势粒的趋势,减库处理相应粒位的R0降低,D增加;下部强势粒和弱势粒的粒重差异不随减库强度的增加而显著减小;单粒胚乳细胞数与单粒重极显著正相关,弱势粒单粒重与R0和各增殖时期持续时间显著相关。综上可见,上部强势粒和下部弱势粒充实程度(粒重)存在差异,这种差异可能与弱势粒胚乳细胞增殖速度慢、最终数目少有关,通过减库增源能使下部弱势粒粒重显著增加,但弱势粒发育仍达不到强势粒水平,说明库源关系对弱势粒发育有影响,但弱势粒本身库活性才是制约自身发育的主要因素。

Researches showed that the insufficient of nutrition supply was one reason for poor development of endosperm in rice,however, how much does this suppression effect has, was not very clear. So, a EPT-rice with large-spike cultivar was selected as material to compare the development of endosperm between the grains of first and second branches using gradient reducing sink treatment. A Logistic equations was used to simulate endosperm cell proliferation of grains on different parts of rice panicle,for researching the correlation between grain weight and the number of endosperm cell. The results showed: The number of endosperm cells at superior grain of upper parts of a panicle improved with the increasing of source-sink ratio after the treatment of reducing sink. It could achieve the optimal level under natural conditions. However, those cell numbers of inferior grain at lower parts of a panicle were poorer than all of the superior grain, especially lower than superior grain of upper parts of a panicle. Logistic fitting parameters showed that the initial cell proliferation potential(R0) was the upper< the middle< lower and the superior grain > inferior grain. Effective proliferation period of endosperm cell(D) showed the upper > the middle > the lower, and the superior grain > inferior grain. After the treatment of reducing sink, the R0 dropped and the D increased. The difference of grain weight between superior grains and inferior grains of the same position was not significantly reduced with increasing the source-sink ratio. The sink-source relationship is not the main factor limiting inferior grains development.Significantly positive correlation existed between the endosperm cell number of one grain and single grain weight(SGW). The significant correlation also existed among SGW, R0 and the durations of cell proliferation. These results suggest that the difference of the SGW between upper superior grains and lower inferior grains was because of the slower endosperm cell proliferation and the less number of cells. The grain weight would significant increased by reducing sink and increasing source, and the inferior grain growth was still not up to the level of superior grains. The results showed that inferior grains itself sink activity was the main factor restricted its development.