香樟凋落叶分解过程对两种间作作物生长和光合特性的影响

采用盆栽试验方法,探讨了香樟(Cinnamomum camphora)凋落叶不同土壤添加水平(0 g/盆为CK、25 g/盆、50 g/盆,100 g/盆)对受体作物小白菜(Brassica chinensis)、莴笋(Lactuca sativa)幼苗生长和光合特性的影响。结果显示:(1)香樟凋落叶分解对两种作物的地径、株高、生物量、叶片数和叶面积均有明显的抑制作用,且抑制效应随凋落叶添加量的增加而增强,但随着分解时间的延长其抑制作用逐渐减弱甚至表现为促进作用。(2)香樟凋落叶分解对两种作物的光合色素含量均有明显的抑制效应,并随凋落叶添加量的增加抑制作用增强,且持续时间延长。(3)经凋落叶处理的两种作物叶片净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、水分利用率(WUE)总体上均低于CK,而胞间CO₂浓度(C_i)在各凋落叶处理下均高于CK。(4)随着土壤中凋落叶量的增加,两种作物在光饱和以及CO₂饱和状态下的最大净光合速率(P_{n max})、表观量子效率(AQY)、羧化速率(CE)、光呼吸速率(R_p)和暗呼吸速率(R_d)均不断下降,而光补偿点(LCP)、光饱和点(LSP)、CO₂饱和点(CSP)、CO₂补偿点(CCP)因受体作物的不同,表现出不同的变化趋势。研究表明,土壤中香樟凋落叶分解释放的化感物质,能通过降低受体作物的光合色素合成和光合能力,限制其营养生长,最终影响生物量积累;相对于莴笋,小白菜对香樟凋落叶分解产生的化感胁迫效应具有更强的耐受性,可能更适宜在香樟林间种植。

Allelopathic Effect of Cinnamomum camphora Leaf Litter on Growth and Photosynthetic Characteristics of Two Intercropping Crops

A pot experiment was conducted to investigate the allelopathic effect of decomposing leaf litter of camphor(Cinnamomum camphora) on the growth and photosynthetic characteristics of the two recipient crops [cabbage(Brassica chinensis) and lettuce(Lactuca sativa)].Four levels of leaf litter addition were applied to soil [namely 25,50 and 100 g·pot^-1) and CK(no leaf litter added)].The results showed that:(1)the decomposing camphor leaf litter showed inhibition effect on ground diameter,plant height,biomass,leaf number and leaf area of the two recipient crops.The inhibition effect to the recipient crops was enhanced with the increment of leaf litter,but with the extension of decomposition time the inhibition effect tended to weaken and even showed the promotion effect on recipient crops;(2)Leaf litter decomposition showed significant inhibition effect on photosynthetic pigment content of both crops,and the inhibition effect enhanced with the increment of leaf litter;(3)Application of leaf litter reduced the net photosynthetic rate(P_n),stomatal conductance(G_s),transpiration rate(T_r) and water use efficiency(WUE) and the intercellular CO₂ concentration(C_i) in all treatments;(4)With the increasing amount of leaf litter in soil,the maximum net photosynthetic rate(P_{n max}),apparent quantum efficiency(AQY),RuBP carboxylation efficiency(CE),light respiration rate(R_p) and dark respiration rate(R_d) of two crops were declined under the saturation condition of light and CO₂,but the light compensation point(LCP),light saturation point(LSP),CO₂ saturation point(CSP),CO₂ compensation point(CCP) showed different trends due to different recipient crops.Overall,this study suggested that,decomposing camphor leaf litter may release the allelochemicals which could reduce the chloroplast pigment synthesis and weaken the photosynthetic capacity of recipient crops,limit the vegetative growth of crops,and ultimately affect the biomass accumulation.Compared with lettuce,cabbage has the stronger tolerance to the inhibition effect of decomposing camphor leaf litter.It may be more suitable for intercropping with camphor.