水分亏缺对小麦灌浆中后期穗部光合特性和^(14)C-同化物转运的影响

Photosynthetic Characteristics and ^(14)C-Assimilate Translocation in Wheat Spike during Mid-to Late-filling Stage under Water Deficit

为探讨水分亏缺对小麦灌浆中后期穗部同化物转运的影响,利用14CO2同位素示踪技术,对于2个抗旱性不同小麦品种的盆栽试验,测定中度水分亏缺下小麦穗部光合特性及灌浆中后期碳同化物的转运。结果表明,花后20 d,中度水分亏缺下水地品种郑引1号旗叶和穗部净光合速率(Pn)分别下降50.2%和19.9%,旱地品种普冰143分别下降33.7%和12.8%,后者显著小于前者。14CO2示踪试验表明,花后15~20 d籽粒中14C-同化物快速积累,花后25 d达到最高值;灌浆中后期(花后15~20 d)穗部苞片中14C-同化物向外快速转运,灌浆末期(25 d)碳同化物已彻底转移。成熟期,中度水分亏缺下小麦籽粒中14C-同化物积累高于正常供水处理,且旱地品种普冰143积累量高于水地品种郑引1号。中度水分亏缺下,郑引1号产量下降36.7%,高于普冰143的23.2%。适度水分亏缺对旱地品种穗部净光合影响较小,并促进了灌浆中后期穗部苞片中碳同化物的向外转运,可能是维持旱作小麦稳产的生理基础。

The objective of this study was to understand the effect of water deficit on photosynthetic and assimilate translocation in wheat spike during mid- to late-filling stage by using two pot-cultured 14C-labelled varieties differing in drought tolerance. Under moderate water deficit, the net photosynthetic rate （Pn） of flag leaf and spike at 20 days after anthesis （DAA） decreased by 50.2% and 19.9% in Zhengyin 1 （drought sensitive） and by 33.7% and 12.8% in Pubing 143 （drought tolerance）, respectively. Obviously, the decrease of photosynthetic capacity in the drought-sensitive variety was greater than that in the drought-resistant variety in response to water stress. The 14C-assimilates accumulated rapidly in grains during 15-20 DAA and reached the peak at 25 DAA. Simultaneously, the 14C-assimilates in glume, lemma, and awn had a quick outward transportation during 15-20 DAA, and completely transferred to grains at 25 DAA. Compared with normal water condition, moderate water deficit resulted in significantly higher laC-assimilates in grains at maturity. The 14C-assimilate accumulation in Pubing 143 was significantly higher than that in Zhengyin 1, and the yield loss caused by drought stress was 23.2% in Pubing 143 and 36.7% in Zhengyin 1. Compared with ＆ought-sensitive variety, drought-tolerant variety received less influence of moderate water deficit on spike Pn and stronger assimilate translocation from spike bracts to grain. This might be the physiological basis of stable yield in drought-resistant wheat variety.