施氮水平对4个景观树种光合特性及抗旱性影响

Effects of Nitrogen Application Levels on Photosynthetic Characteristics and Drought Resistance of Four Landscape Tree Species

为探讨施氮水平对景观树种光合特性的影响及其抗旱性提升方面的应用潜力,以深山含笑、秋枫、美丽异木棉、紫薇为研究对象,采用盆栽法,测定并分析了0、0.4、0.8、1.2、1.6 g/L硝酸铵处理下4个树种幼苗的光合参数及其对干旱胁迫下施用0、0.4、0.8、1.2 g/L硝酸铵的生长、生理响应差异。结果显示:(1)各施氮水平对各树种幼苗叶片净光合速率(P_(n))日变化趋势无明显影响,其中深山含笑、紫薇存在光抑制现象;施氮显著影响了4个树种幼苗叶片P_(n)、蒸腾速率(T_(r))、气孔导度(G_(s))、胞间二氧化碳浓度(C_(i))、叶绿素含量(C_(c)),且存在“低促高抑”的现象。(2)P_(n)与T_(r)呈极显著正相关线性关系,P_(n)、T_(r)分别与G_(s)呈显著正相关线性关系,P_(n)与C_(i)、C_(c)均无明显相关性(P>0.05),但C_(i)与C_(c)显著线性正相关。(3)在40%土壤含水率条件下,供试4个树种幼苗均遭受到了干旱胁迫,幼苗存活率下降,生物量增量降低,叶片水分亏缺率增大,P_(n)、T_(r)、G_(s)、C_(i)、C_(c)减小,超氧化物歧化酶活性减弱,丙二醛含量升高。(4)采用11个指标进行评价,干旱胁迫下深山含笑、紫薇以0.8 g/L硝酸铵处理的生长表现最好,而秋枫、美丽异木棉以1.2 g/L硝酸铵处理效果佳。研究结果表明,施氮能改变供试景观树种的光合特性及其抗旱性,但宜根据树种生长、生理特性进行用氮量的精准控制。

In order to explore the effect of nitrogen application level on the photosynthetic characteristics of landscape tree species and its application potential in improving drought resistance,taking Michelia maudiae,Bischofia javanica,Ceiba speciosa and Lagerstroemia indica as the research objects,the pot method was used to determine and analyze the photosynthetic parameters of four tree species seedlings under 0,0.4,0.8,1.2 and 1.6 g/L ammonium nitrate treatment and their growth physiological response differences to 0,0.4,0.8 and 1.2 g/L ammonium nitrate under drought stress.The results showed that:(1)Nitrogen application level had no significant effect on the diurnal variation trend of net photosynthetic rate(P_(n))of seedlings of each tree species,and there was photoinhibition in M.maudiae and L.indica.(2)P_(n),transpiration rate(T_(r)),stomatal conductance(G_(s)),intercellular carbon dioxide concentration(C_(i))and chlorophyll content(Cc)of the four tree species seedlings were significantly affected by nitrogen application levels.(3)P_(n) and T_(r)(R^(2)=0.97,P<0.01),P_(n) and G_(s)(R^(2)=0.95,P<0.05),T_(r) and G_(s)(R^(2)=0.93,P<0.05)showed extremely significant or significant positive correlation linear relationship.P_(n) had no significant correlation with C_(i) and C_(c)(P>0.05),but C_(i) was significantly positively correlated with C_(c)(R^(2)=0.90,P<0.05).(4)The results of principal component analysis showed that the growth of M.maudiae and L.indica treated with 0.8 g/L ammonium nitrate under drought stress was the best,while that of B.javanica and C.speciosa treated with 1.2 g/L ammonium nitrate was the best.The results indicated that nitrogen application could change the photosynthetic characteristics and drought resistance of the tested landscape tree species.However,different tree species had different nitrogen application rates,and the nitrogen application rate should be accurately controlled according to the physiological characteristics of tree species.