不同供钾水平对小麦旗叶光合速率日变化的影响

THE EFFECT OF DIFFERENT LEVELS OF POTASSIUM NUTRITION ON THE DIURNAL VARIATION OF PHOTOSYNTHETIC RATES OF WHEAT FLAG LEAVES

在田间栽培条件下 ,研究了不同供钾水平对小麦 (Triticumaestivum)‘安农 890 3’旗叶光合速率日变化的影响。结果表明 :从扬花期到灌浆中期 (5月 1～ 2 0日 ) ,植株及叶片中钾含量随不同供钾水平的提高而增大 ,尤以施K82 .5kg·hm-2 的增幅较大 (2 .7倍 )。在小麦籽粒的灌浆进程中 ,植株的含钾量不断增加 ,但叶片中的含钾量却呈下降趋势。扬花期到灌浆中期的小麦旗叶由于高光强、高温和较低的相对湿度 ,其气孔导度和净光合速率日变化均呈双峰曲线。两者皆在 10∶0 0左右和 15∶0 0左右各有一个峰值 ,前一峰值高于后一峰值 ,两峰之间的低谷在 14∶0 0左右。胞间CO2 浓度日变化则呈相反趋势 ,两个低谷出现于 12∶0 0和 15∶0 0 ,但灌浆中期时日变化曲线中只有一个低谷。土壤增施钾肥可增大小麦旗叶的气孔导度和净光合速率 ,减轻 10 %～ 37%由光合午休造成的CO2 同化量损失 ,提高小麦产量。但施钾量与胞间CO2 浓度之间相关性不显著。 4种不同的钾素水平处理中以施用K2 O 16 5kg·hm-2

A study on the effects of different levels of potassium nutrition on the diurnal variation of the photosynthetic rate of flag leaves of wheat (Triticum aestivum cv. Anlong 8903) planted in the fields showed that from flowering stage to middle grain filling stage (May 1-20), the potassium content in the plants and leaves increased with increasing levels of potassium nutrition. Potassium content in the plant and leaves reached maximum levels that were 2.7 times the control at application rates of 82.5 kg potassium·hm -2, whereas at higher application rates of 330 kg·hm -2, potassium levels were lower (about 10%-30%). During the course of grain filling, the potassium content of the plants increased but that of the leaves decreased. From flowering stage to middle grain filling stage, the diurnal variation of stomatal conductance and of net photosynthetic rate revealed two maxima at about 10∶00 and 15∶00 because of the strong intensity of sunlight, high temperature and relatively low humidity. The maximum at 10∶00 is higher than that at 15∶00, with a minimum at 14∶00. However, the diurnal variation of the intercellular CO 2 concentration (C i) showed a contrasting tendency with two minima at about 12∶00 and 15∶00, and the former was lower than the latter. The maximum C i level between the two minima was most pronounced at flowering stage but less pronounced at the middle grain filling stage. The results showed that increasing the potassium nutrition in the soil can increase stomatal conductance and net photosynthetic rates, and reduce the loss of photosynthetic CO 2 fixation caused by photosynthetic midday depression by 10%-37% thereby raising the wheat output. The correlation between potassium content and intercellular CO 2 concentration was not significant. The results of this study indicate that potassium additions of 165 kg K 2O·hm -2 is the most economically efficient and optimal strategy for increasing net photosynthetic rates and thus wheat yields.