施肥水平对巨桉幼树叶片气体交换日变化的影响

Effects of fertilization level on diurnal variation of gas exchange of young Eucalyptus grandis leaf

以巨桉幼树为对象,研究了不同施肥水平(每株施用含N、P2O5和K2O各15%的复合肥0、90、180和270g)下巨桉叶片的气孔导度(Gs)、胞间CO2浓度(Ci)、净光合速率(Pn)、蒸腾速率(Tr)、水分利用效率(WUE)和叶面饱和水汽压亏缺(Vpdl)日变化,及其叶绿素含量变化,探讨巨桉光合特性与施肥和环境因素之间的关系.结果表明:各处理巨桉叶片Pn的日变化呈"单峰"形曲线,峰值出现在14:00,未出现光合"午休"现象;Gs、Tr和Vpdl的日变化与Pn相同,而Ci的最低值出现在14:00;WUE的日变化呈"双峰"形曲线,峰值分别出现在10:00和14:00.与对照处理相比,施肥处理叶片Gs、Pn、Tr、WUE及叶绿素a、叶绿素b和总叶绿素含量平均值分别增加4.6%～15.9%、7.8%～21.8%、4.8%～11.6%、3.2%～8.8%、15.5%～62.0%、14.5%～44.5%和15.3%～57.1%,且随施肥量的增加而增加;而叶片Ci和Vpdl平均值分别降低1.7%～4.6%和6.4%～15.2%,且随施肥量的增加而降低.气温、相对湿度(RH)和光合有效辐射(PAR)与Gs、Pn和Tr,Gs与Pn和Tr均显著相关.施肥可以促进巨桉生长、提高水分利用效率和增加生物固碳能力;气温、RH、PAR和Gs是影响巨桉光合作用和蒸腾作用日变化的主要因素.

Different levels（0,90,180,and 270 g per tree） of compound fertilizer containing 15% N,15% P 2 O 5,and 15% K 2 O were applied to young Eucalyptus grandis to study the diurnal variations of its leaf stomatal conductance（G s）,intercellular CO 2 concentration（C i）,net photo-synthesis rate（P n）,transpiration rate（T r）,water use efficiency（WUE）,and vapor pressure deficit on leaf surface（V pdl） as well as the variation of leaf chlorophyll content,aimed to approach the relationships of E.grandis photosynthesis with fertilization and environmental factors.In all treatments,the diurnal variation of P n presented a single-peak curve,with the peak at 14：00 and not showing midday depression.The G s,T r,and V pdl showed the similar trend with P n,while the C i had a minimum value at 14：00.The WUE demonstrated a double-peak curve,with the first and second peak occurred at 10：00 and 14：00,respectively.Comparing with the control,the mean values of G s,P n,T r,WUE,and chlorophyll a,chlorophyll b,and total chlorophyll contents under fertilization increased by 4.6%-15.9%,7.8%-21.8%,4.8%-11.6%,3.2%-8.8%,15.5%-62.0%,14.5%-44.5% and 15.3%-57.1%,respectively,and the increment increased with fertilization level.By contrast,the mean values of C i and V pdl decreased by 14.5%-44.5% and 15.3%-57.1%,respectively,and the decrement increased with fertilization level.The G s,P n,and T r were significantly correlated with air temperature,relative humidity（RH）,and photosynthetic active radiation（PAR）,and also,the G s was significantly correlated with P n and T r.It was suggested that fertilization could promote E.grandis growth and enhance its WUE and biological carbon sequestration,and air temperature,RH,PAR,and G s were the main factors causing the diurnal variations of photosynthesis and transpiration of E.grandis.