Abstract

In order to study the effect of decomposition of eucalyptus leaf litter on crops in agroforestry ecosystems, a pot experiment was conducted with five treatments, that is, 0 (the control), 30, 60, 90, and 120 g of blue gum (Eucalyptus maidenii) leaf litter were mixed with 10 kg of soil, namely CK, L30, L60, L90, and L120, respectively. Spinach (Spinacia oleracea), the selected receptor, was seeded for each treatment. Several morphological and physiological indicators of spinach were determined 50 days later. The results were shown as follows: (1) Significant stimulation was observed in the bolting length, rate of bloomed plants and rachis length treated with the leaf litter, except L120 in the bolting length. On the contrary, the root shoot ratio (R/S) and leaf area from leaf litter treatments were both considerably lower than those from CK. (2) As the leaf litter increased, the ratio of soluble sugar content to soluble protein content (SS/SP) rose accompanied with the descent of the leaf area (r=-0.9298, n=5, p<0.05). (3) The peroxidase (POD) activity was promoted, while the superoxide dismutase (SOD) and catalase (CAT) activity were inhibited by L60 to L120. The lipid peroxidation determined using the malondialdehyde (MDA) assay was promoted by each leaf litter treatment. Based on the data stated previously, it is suggested that decomposition products of blue gum leaf litter induces the maturation and senescence of spinach via hormones or/and reactive oxygen species (ROS).

Key words: Blue gum, spinach, decomposition, maturation, senescence, allelopathy.