混播白羊草和达乌里胡枝子叶片光合生理特性对水分胁迫的响应

Leaf Photosynthetic Characteristics of Bothriochloa ischaemum and Lespedeza davurica in Mixtures under Water Stress

以黄土丘陵半干旱区白羊草(Bothriochloa ischaemum)和达乌里胡枝子(Lespedeza davurica)为研究对象,通过盆栽控制试验,设置3种土壤水分处理水平(HW、MW和LW,分别为田间持水量的80%±5%,60%±5%和40%±5%)和7个株数比例组合(株数比为0∶12、2∶10、4∶8、6∶6、8∶4、10∶2和12∶0),分析比较白羊草和达乌里胡枝子拔节期、开花期和结实期的叶片光合生理参数,探讨不同土壤水分和草种组合比例下二者叶片光合气孔交换参数随生育期动态变化规律,揭示水分胁迫下2种乡土草混播共存的生理生态机制。结果显示:(1)水分胁迫显著降低了2种草叶片净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs),且以白羊草的光合生理响应更为敏感;除LW土壤水分下达乌里胡枝子结实期的Pn降低原因为非气孔限制因素外,其余处理下均为气孔因素。(2)HW土壤水分下,白羊草混播下的Pn均值显著高于单播,但达乌里胡枝子呈相反趋势;MW和LW土壤水分下,白羊草混播下拔节期与开花期以及达乌里胡枝子结实期的Pn均显著高于各自单播,白羊草各生育期的水分利用率(WUE)均显著高于达乌里胡枝子。(3)在10∶2混播条件下,LW土壤水分处理的白羊草各生育期的Pn和WUE、以及MW和LW土壤水分处理的达乌里胡枝子结实期的Pn和WUE均显著高于各自单播。研究表明,白羊草与达乌里胡枝子株数比为10∶2时,有利于提高水分胁迫条件下二者叶片光合速率和水分利用效率。

The photosynthetic characteristics of Bothriochloa ischaemum and Lespedeza davurica in the loess hill-gully was investigated under potted condition, the photosynthetic gas exchange parameters of two species during the heading period, flowering period and mature period were studied under three soil water regimes （HW, 80%±5% of field capacity（FC）;MW, 60%±5% of FC;LW, 40%±5% of FC） and seven plant mixture ratios （i.e.0∶12, 2∶10, 4∶8, 6∶6, 8∶4, 10∶2 and 12∶0, respectively）.The objectives were to determine the leaf photosynthetic characteristics of two species across their growth periods under different mixture ratios, and to identify their co-existence mechanisms of two native species under lower water availability.The results showed that： （1） the net photosynthetic rate （Pn）, stomatal conductance （Gs） and transpiration rate （Tr） of two species were decreased under water stress, and the photosynthetic response of B.ischaemum was more sensitive to water stress;water stress decreased photosynthesis of both species during growth periods were caused by stomatal limitation, except for the species of L.davurica in the mature period under LW soil water regime;（2） under HW soil water regime, the averaged Pn values of B.ischaemum in mixtures were significantly improved, whereas adversely affected L.davurica throughout the growing season;Under MW or LW soil water regimes, Pn in mixtures showed higher values when B.ischaemum in heading period or flowering period and L.davurica in mature period, compared to respective monoculture, and the water use efficiency （WUE） of B.ischaemum were significantly higher than that of L.davurica in different growth periods;（3） when the B.ischaemum and L.davurica at a mixture ratio of 10∶2, the Pn and WUE of B.ischaemum in different growth periods under LW regime, and the Pn and WUE of L.davurica in mature period under the MW or LW regimes, which were significantly higher than that of the species in monoculture.These results suggested that the B.ischaemum and L.davurica at a mixture ratio of 10∶2 improved the leaf photosynthesis and water use efficiency of both species under low soil moisture condition.