CO_2浓度升高加快水稻灌浆前期籽粒的生长发育进程

Acceleration of Grain Growth and Development Process by FACE during Early Grain Filling Stage of Rice(Oryza sativa L.)

本研究利用开放式空气中CO2浓度增加（Free Air CO2 Enrichment,FACE）试验平台,研究CO2浓度升高200 μmol·mol^-1下,水稻灌浆早期籽粒大小、生长速率、可溶性碳水化合物和淀粉含量及蔗糖转化酶活性等在开花后20 d内的变化动态.结果表明,与对照相比,FACE处理加快了灌浆早期籽粒的发育进程,尤其加快了籽粒宽度达到最大的日程,籽粒大小和籽粒灌浆速率提前3 d达到最大值;成熟时籽粒的长宽积FACE下的比对照下的提高了4.5%,但粒重无差异;FACE下开花后2～5 d内籽粒中的还原糖和蔗糖的含量及细胞壁转化酶和细胞质转化酶的活性显著高于对照下的,但淀粉含量和可溶性酸性转化酶活性则无显著差异.从结果推论,FACE加速水稻灌浆前期籽粒生长发育与其花后早期颖果内蔗糖合成和转运水平之间可能存在内在联系.

It is forecasted that atmospheric CO2 concentration till the middle of this century will be risen to about 550 μmol·mol^-1. Several experiments have shown that the yield of rice will be significantly increased by elevated CO2 as a result of an increase in number of grain per panicle or per plant. Less attention has been paid to the effect of elevated CO2 on the process of grain growth and development. This experiment was conducted to determine the grain growth and development during early stage of grain filling of rice （ Oryza sativa L. subsp, japonica, cv. Wuxiangjing-14） under the conditions of ambient atmosphere CO2 concentration （CK） and FACE （ Free Air CO2 Enrichment, 200 μmol· mol^-1 higher than ambient） with 3 repetitions. The grain width, length and their product, contents of soluble carbohydrate （reducing sugar and sucrose） and starch, and activities of invertases including cell wall invertase （CWI）, soluble acid invertnse （SAI）and neutral invertase （NI） in grain were measured. Dry matter and filling rate on the basis of dry weight of grain with sampling every 3 days from anthesis till mature period, and grain weight and size at maturity were tested. The results showed that the process of growth and development of grain was accelerated and width and length of caryopsis were significantly increased by FACE. The maxima of grain width and size, and grain filling rate under FACE were about 3 days earlier than those under CK. The product of mature grain width and length under FACE was increased by 4.5% of CK. However, such obvious effect was not shown in the final grain weight （Fig. 1, Fig.2）. The contents of reducing sugar and sucrose, which were needed as materials and energy substance for the normal growth and development of grain, were increased during 1 week after anthesis （Fig.3）, while the activities of CWI and NI enhanced during 5 days after anthesis by FACE （Fig.4）. However, the content of starch and activitie of SAI in grain were not affected by elevated CO2. In conclusion, higher contents of soluble carbohydrate and higher activities of CWI and NI under FACE supply more materials for the growth of larger grain sink capacity. There is no significant effect on the final grain dry weight resulting from a slight increase in sink activities and the earlier decrease in grain filling rate under FACE. A new balance between sink and source needs to be established under elevated CO2 condition in order to improve grain yield by means of increasing the grain weight on the basis of higher panicle grain number in rice.