与达乌里胡枝子混播下白羊草光合对干旱及短期补水的响应

Photosynthetic response of Bothriochloa ischaemum(L.) Keng to drought and short-term rewatering when intercropped with Lespedeza davurica(Laxm.)Schindl. in a pot experiment

为揭示黄土丘陵区优良乡土草种白羊草[Bothriochloa ischaemum(L.)Keng]和达乌里胡枝子[Lespedeza davurica(Laxm.)Schindl.]混播时的光合生理特征及其与土壤水分的关系,采用盆栽控制试验,按照生态替代法设置了白羊草(B)和达乌里胡枝子(D)6种混播比例组合(2︰10、4︰8、6︰6、8︰4、10︰2、12︰0),标记为B2D10、B4D8、B6D6、B8D4、B10D2、B12D0;设置高水(80%土壤田间持水量,HW)、中水(60%土壤田间持水量,MW)和低水(40%土壤田间持水量,LW)3种水分供应条件,并在白羊草拔节期进行短期补水处理:即分别从中水提到高水(MHW)、低水提到高水(LHW)和低水提高到中水(LMW)。连续测定和比较了不同处理下白羊草光合生理特征——净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和水分利用效率(WUE)的动态变化。结果表明:1)在恒定水分供应条件下,各混播比例中白羊草叶片光合生理参数在HW处理下显著最高,LW处理下显著最低,说明水分是限制其叶片光合作用的主要因子;2)短期补水后,白羊草叶片光合生理参数均是在LHW下增加幅度最大,LMW下增加幅度最小;各混播比例中白羊草光合生理参数在MHW下恢复到稳定水平时间最快,说明较高的补水幅度和土壤前期含水量有利于补水后叶片光合作用提高;3)在B10D2和B8D4混播比例下,白羊草不仅具有较高的Pn、较低的Tr和较高的WUE,且短期补水后Pn和WUE增加幅度较大,Tr增幅较小,说明这两种混播比例有利于改善其光合作用。综合表明,经历短期干旱胁迫后补水,白羊草光合生理活性出现恢复现象,恢复速度和程度与混播比例和补水前土壤水分水平相关。

To clarify photosynthetic characteristics and their relationship with soil water conditions of Bothriochloa ischaemum （L.） Keng intercropped with Lespedeza davurica （Laxm.） Schindl. in the loess hilly-gully region, a pot experiment was conducted in the weather enclosure of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau. B. ischaemum （B） was intercropped with L. davurica （D） in six mixture sowing ratios of 2：10, 4：8, 6：6, 8：4, 10：2, 12：0）, and these combinations were marked as B2D10, B4D6, B6D6, B8D4, B10D2 and B12D0, respectively. Three soil water conditions were set in the experiment, which were high water （80% field capacity, HW）, middle water （60% field capacity, MW） and low water （40% field＆amp;nbsp;capacity, LW）. Additionally, during the elongation stage of B. ischaemum, soil water content was improved separately from MW to HW, LW to HW and MW, respectively, i.e. middle water to high water （MHW）, low water to high water （LHW） and middle water （LMW）. Altogether, there were 36 treatments in the experiment, and each was replicated three times. Photosynthetic characteristics, net photosynthetic rate （Pn）, transpirationrate （Tr）, stomatal conductance （Gs）, water use efficiency （WUE） of B. ischaemum were measured after soil was rewatered. Results showed that under relative stable water conditions （i.e. HW, MW, and LW）, photosynthetic parameters of B. ischaemum were significantly highest under HW treatment, and significantly lowest under LW treatment for all mixture sowing ratios, indicating water was the key factor affecting B. ischaemum photosynthesis. After re-watering, the largest and smallest increases of photosynthetic parameters of B. ischaemum appeared under LHW and LMW respectively. For all mixture sowing ratios, photosynthetic activity of B. ischaemum under MHW recovered to stable level in the shortest time, suggesting that higher water content in early stage and higher rewatering level benefited B. ischaemum photosynthesis improvement. B. ischaemum presented not only higher Pn, lower Tr and higher WUE under B10D2 and B8D4 treatment, but also greater increase in Pn and WUE and smaller increase in Tr after rewatered, implying that the two mixture sowing ratios were beneficial for improving the photosynthesis efficiency of B. ischaemum. The research results suggested that photo-physiological activities of B. ischaemum was recovered after re-watering from short-term drought stress, and the recovery speed and level were correlated with mixture sowing ratio with L. davurica and soil water content before re-watering.