蓝桉凋落叶分解对菠菜生长及光合特性的影响

通过盆栽试验,模拟蓝桉(Eucalyptus globulus)凋落叶在土壤中分解对受体植物菠菜(Spinacia oleracea)生长及光合特性的影响,设置L30(30 g/盆)、L60(60 g/盆)、L90(90 g/盆)和L120(120 g/盆)4个凋落叶施用水平,对照(CK)不加凋落叶。结果表明:(1)在分解30 d时,低量的凋落叶(L30)未抑制菠菜生物量的积累,而中量和高量处理(L60、L90和L120)下其生物量显著降低(P0.05);在凋落叶分解50 d后,蓝桉凋落叶的化感抑制效应已经减弱,仅L120仍然抑制菠菜生物量的积累;(2)一定量的凋落叶(L30和L60)对菠菜叶绿素的合成有促进作用,而凋落叶超过一定量时(L120)转为抑制作用,在凋落叶分解28 d时相对不明显,40 d后逐渐显现;(3)经凋落叶处理的菠菜叶片胞间CO2浓度(Ci)、气孔导度(Gs)及蒸腾速率(Tr)均显著高于对照(CK)(P0.05),而净光合速率(Pn)在L30处理下最高,L60和L90处理与CK差异不显著,仅L120处理显著低于CK(P0.05);(4)光响应与CO2响应曲线的特征参数表观量子效率(AQY)、最大净光合速率(Pmax)、光饱和点(Lsp)、光补偿点(Lcp)、暗呼吸速率(Rd)、Ru BP表观羧化效率(CE)和光呼吸速率(Rp)在L30处理下高于CK,其余凋落叶处理均低于CK,而CO2饱和点(Csp)、CO2补偿点(Ccp)随凋落叶量的增加而升高。综合各指标可见,少量的蓝桉凋落叶分解(L30)可通过增加叶绿素含量,提高对光和CO2的利用能力促进菠菜的光合作用,进而促进其生长,而凋落叶超过一定量时(L90—L120)则起到相反的作用。

The effect of decomposing leaf litter of blue gum (Eucalyptus globulus) on the growth and photosynthetic characteristics of spinach (Spinacia oleracea)

A pot experiment was conducted to study the effects of decomposing leaf litter of blue gum (Eucalyptus globulus) on the growth and photosynthetic characteristics of spinach (Spinacia oleracea). Four levels of leaf litter addition were set as follows: CK (the control, 0 g/pot), L30 (30 g/pot), L60 (60 g/pot), L90 (90 g/pot) and L120 (120 g/pot), and each pot contained 10 kg of soil for mixing with the leaf litter. The results showed that: (1) A low dose of leaf litter (L30) did not affect the biomass accumulation of spinach on the 30^th day of decomposition, while a medium and high dose of leaf litter (L60-L120) suppressed it visually (P < 0.05); When the duration of decomposition reached 50 d, both L30 and L60 stimulated the accumulation of the biomass of spinach, and no significant difference existed between L90 and CK, while the effect of L120 was still suppressive, indicating a languishment of the inhibition of leaf litter decomposition. (2) The effects of leaf litter decomposition on the photosynthetic pigments of spinach also varied with increasing time and leaf litter amount. Positive effect was observed at L30 and L60 in the chlorophyll content, while L120 converted this effect. However, the effects of these leaf litter treatments were not apparent until the 40^th d. (3) The intercellular CO₂ concentration (Ci), stomatal conductance (Gs) and transpiration rate (Tr) were all significantly higher than those of the control (P < 0.05), while the peak value of the net photosynthetic rate (Pn) appeared at L30, which were statistically the same with that under the CK at L60 and L90, moreover, significant decrease was only observed at L120 (P < 0.05); (4) As for the parameters of light response curve and CO₂ response curve, the apparent quantum yield (AQY), maximum net photosynthetic rate (P_max), near light saturation point (Lsp), light compensation point (Lcp), dark respiration rate (Rd), RuBP apparent carboxylation efficiency (CE) and photorespiration rate (Rp) all showed a trend of increasing at L30 and decreasing gradually with increasing leaf litter, while CO₂ saturation point (Csp) and CO₂ compensation point (Ccp) increased with the increase of leaf litter. In sum, a small amount of blue gum leaf litter (treatment L30 in present study) could promote the chlorophyll content and the light / CO₂ use efficiency of spinach, and thus stimulated its growth, but a high level of leaf litter (treatment L90 and L120) reversed this effect.