西南喀斯特地区小叶黄杨与白刺花光合特性研究

Study on photosynthetic characteristics of Buxus microphylla and Sophora davidii in the karst area of southwest China

本试验选择晴天,利用英国Lcpro+光合测定仪对西南喀斯特石漠化地区的小叶黄杨和白刺花的光合日变化特征进行了测定。结果表明:小叶黄杨的日均净光合速率为(2.66±0.69)μmolCO_2·m^(-2)·s^(-1),远低于白刺花的(7.32±3.87)μmolCO_2·m^(-2)·s^(-1)。小叶黄杨和白刺花的净光合速率和蒸腾速率随着光照辐射增强、气温升高,出于保护自身,被动的关闭部分气孔,造成光合作用原料即胞间CO_2的浓度降低,叶片水分减少,使光合速率和蒸腾速率相对下降,出现一个较为明显或滞后的"午休"现象。小叶黄杨光合生理特性最活跃时间在8:00左右,其他时间段较低的原因可能是其不耐强光和高温,白刺花的光合特性则表现出全天相对较高状态。8:00是小叶黄杨和白刺花同化作用最佳的时间之一,在其他时段小叶黄杨和白刺花的水分利用效率存在较大差异,但存在"高-低-高-低"的交叉变化趋势。整体上讲,白刺花水分利用效率日均值[(1.52±0.84)μmolCO_2·mmol-1H_2O]略高于小叶黄杨[(1.40±0.78)μmolCO_2·mmol-1H_2O],白刺花具有高光合速率、高蒸腾速率、低水分利用效率的特点;小叶黄杨具有低光合速率、低蒸腾速率、低水分利用效率的特点。在石漠化特殊的环境背景下栽植饲用灌木要充分考虑不同时间节点的光合特点,采取必要措施,如遮阴、补水等,提高其水分利用效率,发掘潜在生态经济价值。

The diurnal variation of photosynthetic characteristics for Buxus microphylla and Sophora davidii in the karst desertification area of southwest China were measured by using Lcpro+photosynthetic apparatus of England on sunny days.The results showed that the diurnal average net photosynthetic rate of Buxus microphylla was(2.66±0.69)μmol CO2·m^-2·s^-1,which was much lower than that of Sophora davidii[(7.32±3.87)μmolCO2·m^-2·s^-1].The net photosynthetic rate and transpiration rate of Buxus microphylla and Sophora davidii increased with the increase of light radiation and temperature.In order to protect themselves,partial stomata were closed passively,which resulted that the intercellular CO2 concentration and leaf moisture were decreased,the photosynthetic rate and transpiration rate were relatively declined and it was appeared a more obvious or lagged“midday break”phenomenon.The most active time of photosynthetic physiological characteristic for Buxus microphylla was at about 8:00,and the reason for the lower photosynthetic activity in other time periods may be related to its intolerance to strong light and high temperature,while the photosynthetic characteristic of Sophora davidii was relatively high throughout the day.8:00 was one of the best time for the assimilation of Buxus microphylla and Sophora davidii.There was a great difference in water use efficiency between Buxus microphylla and Sophora davidii in other periods,but there was a cross-changing trend of“high-low-high-low”.On the whole,the diurnal average value of water use efficiency for Sophora davidii[(1.52±0.84)μmolCO2·mmol^-1H2O]was slightly higher than that of Buxus microphylla[(1.40±0.78)μmolCO2·mmol^-1H2O].Sophora davidii has the characteristic of high photosynthetic rate,high transpiration rate and low water use efficiency,Buxus microphylla has the characteristic of low photosynthetic rate,low transpiration rate and low water use efficiency.Planting the economic forest under the special environment background of rocky desertification,we must fully consider the photosynthetic characteristics at different time points and take necessary measures(such as shading and replenishing water)to increase its water use efficiency and explore potential ecological and economic values.