Supplemental light is often used in fruit production, but few studies have been conducted on pitaya.  In this study, supplemental blue light was applied to pitaya for four hours each night in the field from flowering to fruit ripening to examine changes in peel and pulp physicochemical parameters and metabolites.  Blue light treatment significantly increased fruit weight, improved fruit firmness by increasing pectin content and retarding hemicellulose degradation, and enhanced antioxidant enzyme activity.  Blue light had minor effects on primary metabolites but more pronounced effects on volatiles.  By affecting alanine, aspartate and glutamate metabolism, blue light treatment resulted in significant fruit growth, increased accumulation of bioactive ingredients in the peel, and significantly altered the accumulation of flavor-associated volatile compounds, such as organic acids, esters and terpenes in the pulp.  Our results provide an important reference for improving the yield and quality of pitaya production using supplemental light in the field.

Vegetable fields are often contaminated by heavy metals, and Spodoptera exigua is a major vegetable pest which is stressed by heavy metals mainly by feeding.  In this study, cadmium accumulation in the tissues of S. exigua exposed to cadmium and its effects on the growth and development of the parents and the offspring were investigated.  Under the stress of different concentrations of cadmium (0.2, 3.2, and 51.2 mg kg^–1), the cadmium content in each tissue of S. exigua increased in a dose-dependent manner.  At the larval stage, the highest cadmium accumulation was found in midgut in all three cadmium treatments, but at the adult stage, the highest cadmium content was found in fat body.  In addition, the cadmium content in ovaries was much higher than in testes.  When F₁ S. exigua was stressed by cadmium and the F₂ generation was not fed a cadmium-containing diet, the larval survival, pupation rate, emergence rate and fecundity of the F₂ generation were significantly reduced in the 51.2 mg kg^–1 treatment compared to the corresponding F₁ generation.  Even in the F₂ generation of the 3.2 mg kg^–1 treatment, the fecundity was significantly lower than in the parental generation.  The fecundity of the only-female stressed treatment was significantly lower than that of the only-male stressed treatment at the 3.2 and 51.2 mg kg^–1 cadmium exposure levels.  When only mothers were stressed at the larval stage, the fecundity of the F₂ generation was significantly lower than that of the F₁ generation in the 51.2 mg kg^–1 treatment, and it was also significantly lower than in the 3.2 and 0.2 mg kg^–1 treatments.  The results of our study can provide useful information for forecasting the population increase trends under different heavy metal stress conditions and for the reliable environmental risk assessment of heavy metal pollution.