固氮植物绿豆对核桃幼苗生长、叶片气孔气体交换及水力特征的作用

Effects of a nitrogen fixing plant Vigna radiata on growth, leaf stomatal gas exchange and hydraulic characteristics of the intercropping Juglans regia seedlings

采用砂培方法,在温室内将一年生核桃(Juglans regia)嫁接苗木和绿豆(Vigna radiata)进行间作,研究绿豆对核桃苗木生长、水分平衡和光合特性的影响。该研究设有5种处理,即:对照(核桃单作,正常供应氮素);核桃单作,不添加氮素;核桃绿豆间作,不添加氮素;核桃绿豆间作,正常供应氮素;绿豆单作,不添加氮素。结果显示:种植绿豆可以增加土壤氮含量和核桃茎内氮含量,但对核桃叶和根系中的氮含量影响不明显。种植绿豆显著增加不施氮核桃的高生长和直径生长,但降低了正常供氮核桃的生长。无论种植绿豆与否,不供氮处理降低了核桃的总叶面积,提高了根冠比。核桃叶片气孔气体交换对各处理的响应和生长有相同的趋势。缺氮显著降低了核桃叶柄在中午的导水率、提高了导水损失率;种植绿豆显著提高不供氮核桃的导水率而且明显降低了其导水损失率。然而,种植绿豆使正常供氮的核桃降低了导水率,加剧了导水损失率。同时,绿豆受到间作的竞争压力,产量和生物量有所下降。由研究结果可知,在贫瘠的土壤上,固氮植物绿豆改善了间作的核桃的氮营养,有益于核桃木质部发育、水分平衡以及光合代谢。但是在氮充足的土壤中,种植绿豆反而降低了核桃的水分供应,影响其气体交换和生长。

Aims Our main purposes were to determine the effects of Vigna radiata, a nitrogen fixing plant, on growth, wa-ter balance and gas exchange of the intercropping Juglans regia seedlings and to investigate the hydraulic mecha-nism involved in photosynthesis and growth. Methods We measured growth, hydraulic characteristics, and rate of gas exchange in J. regia seedlings, and ana-lyzed the effects of the intercropping nitrogen fixing V. radiata on xylem anatomic structure, water balance and photosynthetic characteristics of J. regia seedlings under conditions of nitrogen deprivation and enrichment. Important findings Under conditions of nitrogen deficiency, the nitrogen fixing V. radiata facilitated the growth of the intercropping J. regia seedlings by improving xylem development, water transport and hydraulic character-istics in high transpiration demand. However, with nitrogen addition, the occurrence of V. radiata inhibited the growth of J. regia seedlings, likely by competing for water and other elements.