摘要
以春性小麦品种扬麦15 8和扬麦11为材料,设置出穗后高氮(HN)和正常氮(NN)两个施肥水平,以正常浇水为对照(WW) ,研究适度土壤干旱(WS)对小麦茎贮藏性碳水化合物运转及有关酶活性的影响。结果表明,土壤干旱改变了小麦茎中碳水化合物的组成和流向,通过诱导小麦茎节间果聚糖外水解酶(FEH)活性的上升,促进了贮藏果聚糖的降解。适度土壤干旱抑制蔗糖代谢过程中由蔗糖合成酶(SuSy)催化的可逆途径,但加强蔗糖磷酸合成酶(SPS)和蔗糖转化酶(INV)催化的单向碳流途径,SPS在茎内蔗糖的合成中起主导作用,促进了开花期喂入的贮藏14 C向蔗糖的分配,在茎贮藏同化物快速运转期(10～30DAA) ,土壤干旱处理使小麦茎中蔗糖含量较正常浇水处理分别提高了15 .9%～19. 0 %(NN)和34. 7%～4 0 . 5 % (HN) ,贮藏14 C向籽粒分配的比例显著提高,茎鞘贮藏性糖对籽粒产量贡献分别是对照(正常浇水处理)的2 . 0～2 . 1倍(NN)和4 . 8～5 . 3倍(HN)。与正常浇水处理相比,土壤干旱使正常施氮处理的籽粒产量降低,而使高氮处理的产量显著增加。
Delayed senescence caused by either too much nitrogen application or an adoption of lodging-resistant cultivars that stay “green” too long results in much non-structural carbohydrate in straw and leads to low harvest index. Heavy use of nitrogen fertilization, especially in highly productive areas, is well known to lead a delayed senescence. Unfavorably-delayed senescence retards the active and ordered process that partitions the photosynthetic assimilates into grains, and results in a decrease in grain weight and yield. A moderate soil drying applied at grain filling period can enhance the plant senescence and may improve the yield through remobilizing more pre-stored food to grains. In current study, the concrete container and pot experiments were conducted at Yangzhou University. Two wheat cultivars were grown with different N levels(high N, HN and normal N, NN) at initial heading in order to have variable development of senescence. A moderate soil drying was imposed from 9 d after anthesis in consideration of that the division of endosperm cell is sensitive to water deficit. The study was designed to test the hypothesis: If a soil drying is controlled properly at mid-late stage of grain filling, an early senescence induced by drought stress would accelerate the rate of grain filling by enhanced relocation of carbon stored reserves, and improved use of pre-stored C reserves, and therefore increase the yield. If so, it would be further evaluated that whose enzymes were up/down-regulated in the remobilized processes of stem-stored carbohydrate response to water deficit. This result showed that pronounced effects of nitrogen application and water-stressed treatment on carbohydrate metabolism were observed in wheat stems. Sugar concentration and carbon distribution among sugar components were altered under soil drying (Fig.2, Fig.3). Degradation of fructan in stems under water deficit was enhanced in wheat through inducing and increasing fructan exohydrolase(FEH) activity (Fig.2, Fig.4, Fig.6). Water stress markedly altered the pattern of sucrose metabolism by shutting down the bypass of carbon flow through the sucrose synthase catalyzed system and enhanced the unidirectional flow through the irreversible sucrose-phosphate synthase(SPS) and sucrose invertase(INV) catalyzed pathway (Fig.2, Fig.3, Fig.5). SPS was induced and activated by water deficit, and played a pivotal role in enhancing synthesis of sucrose through converting stored carbon into sucrose (Fig.5). During rapidly remobilized stage of stored food (10-30 DAA), sucrose contents of wheat stem under water deficit conditions were increased by 15.9%-19.0% (NN) and 34.7%-40.5%(HN)(Fig.3), respectively compared to well-watered treatments. At maturity, the greater proportion of pre-fed 14 C in the stems and sheaths was repartitioned into grain by soil drying under both nitrogen treatments (Fig.7). The grain weight and grain yield under water deficit treatment were significantly decreased at NN, but significantly increased at HN (Table 1). It is concluded that the enhanced remobilization of stored sugar in wheat stem under soil drying conditions was attributed to inducing FEH, increasing SPS activity and activation state, and but decreasing INV activity.
出处
《作物学报》
CAS
CSCD
北大核心
2005年第3期289-296,共8页
Acta Agronomica Sinica
基金
香港研究资助局RGC项目 (2 0 5 2 /0 0M)
国家重点基础研究发展规划项目 (G19990 1170 4)。
