干旱胁迫对樟树幼苗光合特性和水分利用的影响

Effect of drought stress on photosynthetic characteristics and water use of Cinnamomum camphora seedlings

使用LI-6400XT便携式光合作用测量系统对不同水分条件下的樟树幼苗进行光合指标的测定,探究樟树幼苗在干旱胁迫下的自我调节与适应性,为苗期栽培提供参考依据。结果显示:1)在轻度胁迫(LS)、中度胁迫(MS)、重度胁迫(SS)的条件下,樟树幼苗的叶绿素a、叶绿素b、总叶绿素含量与叶绿素a/b均存在先上升后下降的趋势,胁迫结束时均存在显著差异(P <0.05),且重度胁迫(SS)时叶绿素含量下降程度较大,叶绿素a下降幅度略高于叶绿素b,导致叶绿素a/b的比值下降;2)净光合速率(P_n)、气孔导度(G_S)、蒸腾速率(T_r)、胞间CO_2浓度(C_i)在干旱条件下持续下降,在重度干旱(SS)条件下下降幅度最高,各组间差异性显著(P <0.05);3)轻度干旱(LS)与中度干旱(MS)下胁迫结束时水分利用效率(R_(WUE))高于对照组,重度干旱(SS)则略低于对照组;4)在干旱胁迫条件下,一年生香樟幼苗可通过调节叶绿素含量与水分利用情况来适应干旱逆境。

The photosynthetic rate of Cinnamomum camphora seedlings with different drought stress was measured by means of Licor-6400 portable photosynthesis measurement system, than the adaptability of C. camphora seedlings to drought stress was studied, to provide a guideline for seedling cultivation. The results show as follows. 1) Under the conditions of light and modest and severe drought stress, the chlorophyll a, chlorophyll b, total chlorophyll content, chlorophyll a/b all had the trend of rising first and then declining (P < 0.05);the chlorophyll content decreased greatly under severe stress (SS), and the decrease of chlorophyll a was slightly larger than that of chlorophyll b, resulting in a decrease in the ratio of chlorophyll a/b. 2) Net photosynthetic rate (Pn), stomatal conductance (GS), transpiration rate (Tr) and intercellular CO2 concentration (Ci) continued to decline under drought conditions, and decreased most under severe drought (SS) conditions, with significant differences among groups (P < 0.05). 3) At the end of stress under mild drought (LS) and moderate drought (MS), the two groups’ water use efficiency (RWUE) was higher than that of the control group, and severe drought (SS) groups’ RWUEwas slightly lower than the control group. 4) This indicates that under drought stress, annual seedlings can be adapted to drought stress by regulating chlorophyll content and water use.