The effect of supplemental LED night lighting on the growth and physiology of the Para rubber tree

The rubber tree ( Hevea brasiliensis ) is an economically important source of natural rubber. H. brasiliensis grows slowly in southern China mainly because of relatively low temperatures there. The slow growth rate delays plant propagation, so ways of increasing growth are needed. Light is important for regulating plant growth. An extended photophase is commonly used to increase plant growth and development. We studied the effects of an extended photophase, by supplemental LED night lighting, on the growth and physiology of young H. brasiliensis . Night lighting significantly increased plant height, stem diameter, and flush number. Chlorophyll a and total chlorophyll contents significantly increased, while chlorophyll b and carotenoids were unaffected. The photosynthetic parameters, nutrition status, and soluble sugar and protein contents changed little with supplemental lighting. The activities of antioxidases, including superoxide dismutase, peroxidase, and catalase, were similar in the experimental and control plants. The results showed that overnight LED lighting, in addition to solar irradiation during the daytime, could improve the rhythmic growth of H. brasiliensis without causing obvious physiological changes.