Pulses of low intensity light as promising technology to delay postharvest senescence of broccoli

Visible light irradiance may be a useful technology to delay postharvest senescence of green vegetables. In this work, we studied the effects of low-intensity white, red and far red light pulses on postharvest senescence of broccoli stored in the dark at 20 degrees C. Daily exposure for 2 h to 20-25 mu mol m(-2) s(-1) of white light delayed yellowing and retained chloroplast components (chlorophyll and soluble proteins). The utilized light intensity was insufficient to re-initiated photosynthesis since total sugar content was lower than initials in irradiated florets. Light treatment resulted in a slower loss of sugars in comparison with the untreated samples, but was not affected by light quality. The effects of red light treatment on chlorophyll a and soluble protein degradation were similar to white light, and opposite to far red light. However, these treatments did not delay chlorophyll b degradation, suggesting that phytochromes could be involved in molecular mechanism of chlorophyll a and soluble protein degradation, but not of chlorophyll b.