旱地冬小麦生育后期有关光合特性及光合产物分配规律研究

PHOTOSYNTHETIC CHARACTERISTICS AND DISTRIBUTION OF 14C\=ASSIMILATES IN THE WINTER WHEAT OF LATE GROWING PERIOD\=IN DRY LAND

在大田自然干旱条件下旱作处理，冬小麦生育后期旗叶光合速率仍可达１４２４μｍｏｌＣＯ２·ｍ－２·ｓ－１；在叶片水势达－１８～－２１ＭＰａ条件下，旗叶ＲｕＢｐ羧化酶活性可达２０～２３μｍｏｌＣＯ２·ｍｉｎ－１·ｇ－１ｄｗ；浇水处理小麦植株旗叶光合速率为１５１５μｍｏｌＣＯ２·ｍ－２·ｓ－１，水势达－１６５～－１８ＭＰａ条件下，旗叶ＲｕＢｐ羧化酶活性可达２２～２５μｍｏｌＣＯ２·ｍｉｎ－１·ｇ－１ｄｗ；表明在一定干旱条件下，旗叶ＲｕＢｐ羧化酶不是光合速率主要的限制因素，其受干旱影响程度较小。另外，在自然干旱条件下，地上部光合器官旗叶、旗叶鞘、旗叶节间及芒对籽粒的贡献可达４４８％；而浇水处理为４０２％。在生育后期，地上部１４Ｃ光合产物向地下根系运输的比例两处理均为２％左右，但旱作处理１２０～２００ｃｍ土层范围内根系所占有的１４Ｃ产物量占地下根系１４Ｃ产物总量的比率达８３４％，而浇水处理则只有３６％。这些特性对保证旱作栽培冬小麦生育后期的正常生长发育是十分有益的。

The photosynthetic characteristics and distribution of 14C assimilates of winter wheat in late growing period in the field of natural drought condition was studied. The results showed that photosynthetic rate of flag leaves was up to 1424 mol CO2m-2s-1, the ribulose1,5bisphosphate carboxylase (RUBpCase)activity of flag leaves in late growing period in field drought treatment was about 2023 mol CO2min-1g-1dw when the water potential of flag leaves was about-18-21 MPa.The photosynthetic rate of flag leaves of control was 1515 mol CO2m-2s-1. The RUBpCase activity was about 2225 mol CO2min-1g-1dw in the field of irrigated condition when the water potential of flag leaves was about -165-18 MPa,indicating that the RUBpCase activity of flag leaves in drought condition was not a major limiting factor. The total distribution rate of 14C assimilates of flag leaves, flag leaf sheath, flag leaf node and awn to grain in drought treatment was about 448%, and that of control was about 402%. The results also showed that in late growing period the proportion of 14C assimilates to roots in the both drought and control treatment was similar, about 20%. But the amount of 14C assimilates in the roots in the soil layer of 120200cm was up to 834% of the total 14C assimilates in the roots, however, that of control was only about 36%.