钙对乡土树种白枪杆光合特性和荧光参数的影响

Effect of Calcium on the Photosynthetic Characteristics and Chlorophyll Fluorescence Parameters of Native Plant Species of Fraxinus malacophylla

【目的】探究岩溶石漠化地区植物的钙适应机制。【方法】以滇东南乡土树种白枪杆一年生实生袋苗为试验材料,用0、25、50和75 mmol/L 4个浓度梯度的CaCl_(2)溶液浇灌,测定不同钙浓度下白枪杆幼苗生长指标、叶片光合特性、叶绿素荧光参数和光合色素含量。【结果】随钙浓度的增加,幼苗各器官生长量均呈先增加后下降的趋势,苗高、地径和株幅均在50 mmol/L时最大,且苗高和株幅均与CK差异显著(P<0.05),表明该钙浓度有利于白枪杆幼苗生长。光合日变化中,净光合速率(P_(n))与胞间CO_(2)浓度(C_(i))呈负相关,与气孔导度(G_(s))和蒸腾速率(T_(r))呈正相关;P_(n)、G_(s)、水分利用率(WUE)、初始荧光产量(F_(o))、最大荧光产量(F_(m))、PSⅡ最大量子产率(F_(v)/F_(m))、PSⅡ潜在活性(F_(v)/F_(o))和叶绿素含量均随着钙浓度的增加呈先增加后减小的趋势,且均在50 mmol/L达到最大值,表明适宜的钙浓度能促进白枪杆幼苗叶片光合作用;T_(r)随钙浓度的增加呈总体下降趋势,叶绿素a/叶绿素b随钙浓度的增加总体呈上升趋势,且均在75 mmol/L分别达到最小和最大值,说明高浓度钙会抑制植物的光合效率。【结论】白枪杆幼苗生长的较适外源钙浓度为50 mmol/L,钙浓度过高会抑制白枪杆幼苗的生长和光合作用。

[Purpose]To explore the calcium adaptation mechanism of plants in karst rocky desertification areas.[Method]The annual Fraxinus malacophylla seedlings of the native tree species in southeastern Yunnan used as test materials,and four CaCl_(2) solutions with calcium concentration gradients of 0,25,50 and 75 mmol/L were watered,which used to determine the growth indexes,leaf photosynthetic characteristics,chlorophyll fluorescence parameters and photosynthetic pigment content of F.malacophylla seedlings.[Results]With the increase of calcium concentration,the growth of each organ of the seedlings increased first and then decreased.The growth of seedling height,ground diameter,and plant width were all largest at 50 mmol/L,and the seedling height and plant width were significantly different with CK(P<0.05),indicating that the calcium concentration was beneficial to the growth of F.malacophylla seedlings.During the diurnal changes of photosyn-thesis,net photosynthetic rate(P_(n))was negatively correlated with intercellular CO_(2) concentration(C_(i)),and positively correlated with stomatal conductance(G_(s))and transpiration rate(T_(r)).P_(n),G_(s),water use efficiency(WUE),initial fluorescence yield(F_(o)),maximum fluorescence yield(F_(m)),PSⅡmaximum quantum yield(F_(v)/F_(m)),PSⅡpotential activity(F_(v)/F_(o)),and chlorophyl content increased first and then decreased with the increase of calcium concentration,and reached the maximum value at 50 mmol/L,indicating that the appropriate calcium concentration could promote photosynthesis of F.malaco-phylla seedling leaves;T_(r) showed an overall downward trend with the increase of calcium concentration,and chlorophyll a/chlorophyll b showed an overall upward trend with the increase of calcium concentration,reaching the minimum and maximum value at 75 mmol/L,respectively,indicating that high calcium will inhibit the photosynthetic efficiency of plants.[Conclusion]The appropriate exogenous calcium concentration for the growth of F.malacophylla seedlings is 50 mmol/L.When the calcium concentration is too high,it will inhibit the growth and photosynthesis of the lanceolate seedlings.