华北寒旱区3种根茎作物初霜后光合特性及水分利用

为了探求秋末间断降霜期的作物光热因素利用特征,拓宽该季节资源利用阈限,采用LI-6400光合仪监测了华北寒旱区甜菜、苤蓝、芥菜3作物根茎增长期的光合特性。结合叶片蒸腾速率(Tr)和WUE动态,分析了3种作物光合速率(Pn)的日变化限制因素。结果表明,3种作物间断降霜期Pn日变化呈双峰曲线型,甜菜具有对光辐射的数量与质量宽域利用的光反应特征,其日光合累积量是苤蓝的1.13倍,芥菜的1.54倍;相应日蒸腾累积量是苤蓝的1.06倍,芥菜的1.25倍,说明甜菜具有最高的日均水分利用效率。3种作物净光合速率日变化存在午间"Pn低效期",由叶片失水引发的气孔部分关闭与叶肉细胞光合活性降低,是导致"Pn低效期"的主要因素。甜菜相比苤蓝、芥菜,其Tr日变化表现速升期推迟,维谷期增高,缓降期延后的特征,使之成为对间断降霜期光热水资源高效利用并具有较高生产潜力的优势作物。

Photosynthetic Characteristics and Water Use Efficiency of Three Rhizome Crops After First Frost in Cold and Arid Regions of North China

In order to explore the light and heat use characteristics of crops in continuous drop frost period of later autumn and increase resource utilization thresholds of the season, LI-6400 portable photosynthesis system was used to monitor photosynthetic characteristics during rootstock growing stage of beets, kohlrabi and mustard in cold and arid North China. The limiting factors affecting the daily change of P_n(photosynthetic rate) of three crops were analyzed combined with the changes of T_r(transpiration rate) and WUE(water use efficiency). The results showed that the daily changes of P_n of three crops in continuous drop frost period were bimodal curves. Beets possessed the ability of wide region use of light radiation in quantity and quality, and its daily accumulative dry mass were 1.13 and 1.54 times than that of kohlrabi and mustard, respectively; The daily accumulative transpiration amount of beets were 1.06 and 1.25 times than that of kohlrabi and mustard, respectively, indicating that beets had the highest average daily WUE. The diurnal variation of net photosynthetic rate of three crops exist a midday "P_n inefficient" period, and the reasons may be stomata partial closure caused by leaf water loss and low photosynthetic activity of mesophyll cell. Compared with kohlrabi and mustard, T_r daily variation of beets showed a character of postponed rapidly rising stage, higher at bottom keeping stage and delayed descending stage, which make it to be the dominating crop with higher light, heat and water use efficiency, and had higher productive potential in continuous drop frost period.