施水和钾素添加对元宝枫和女贞木质部栓塞的影响

通过干旱胁迫处理(土壤含水量为田间持水量的30%~40%)和正常水分供给(土壤含水量为田间持水量的70%~80%)两种盆栽控制试验, 研究了耐旱树种元宝枫(Acer truncatum)和中生树种女贞(Ligustrum lucidum)枝条木质部栓塞(以导水率损失百分数(Percentage loss of hydraulic conductivity, PLC)衡量)和水势(Water potential, WP)对钾(K)素添加的响应。结果表明: 两个树种PLC的日变化均呈现先升后降的规律, 而WP呈现相反的变化趋势; 添加K素显著提高了两个树种的PLC, 除了干旱胁迫下的元宝枫, 其他树种和处理的PLC随K素含量的增加而增加; K素显著降低了干旱胁迫下元宝枫和女贞的WP,但对正常水分供给下两个树种的WP无显著影响; 元宝枫的平均PLC高于女贞, 平均WP低于女贞。以上结果表明, K素可能通过降低枝条的WP, 促进树种木质部栓塞的形成, 达到限制水分进一步丧失的目的。K素在调节气孔运动、渗透作用等方面的作用, 可能是树种木质部栓塞形成的诱 因。

EFFECTS OF POTASSIUM ADDITION AND WATER SUPPLY ON XYLEM EMBOLISM IN ACER TRUNCATUM AND LIGUSTRUM LUCIDUM

Aims Xylem embolism is a physiological response of tree species to adverse environmental factors, such as water deficit. Potassium plays an important role in plant ability to resist drought. Our objective was to clarify how xylem embolism respond to potassium addition. Methods Tree species, Acer truncatum and Ligustrum lucidum were chosen to study the response of xylem embolism, which was measured as the percentage loss of hydraulic conductivity (PLC), to potassium addition under drought-stressed and well-watered treatments (soil water content of 30%-40% and 70%-80% of field moisture capacity, respectively).Important findings For both species, PLC was higher at 12:30 than at 6:30 and 18:30, while leaf water potential (WP) showed the opposite trend. Potassium addition raised PLC significantly for both species, and the plants with the highest potassium supply generally had the highest PLC. Potassium addition greatly decreased WP of the plants subjected to water deficit. Between the two species, A. truncatum had higher PLC and lower WP. This study suggests that increase in PLC by potassium-addition may result from potassium's effect on water potential and from its controls on stomata movement, cell osmosis, etc.