Effects of light quality on carbon-nitrogen metabolism, growth, and quality of Chinese chives

Abstract

We examined the effect of white + red (WR), white + blue (WB), white + green (WG), white + purple (WP) on the carbon-nitrogen metabolism, growth and quality of Chinese chives, with ‘Pingjiu 2’ as the material and white light (W) as the control. The results showed that photosynthetic rate (Pn) in WR treatment was significantly higher than that in the control (CK) and that there was no difference among WB, WG, WP and CK. The activity of RuBPCase in all the four treatments was higher than that in CK. Compared with other treatments, WR showed the highest total sugar content, then WP, with WB and WG showing the lowest. Compared with CK, sucrose phosphate synthase (SPS) activity in WR was higher, and lower in the other three treatments, especially the lowest in WB. WB showed the highest activity of sucrose synthetase (SS) and amylase (AMS), WR displayed the lowest as well as the similar or lower in WG or WP compared with CK. These results implied that the increases of the proportion of red and purple light could improve carbon assimilation and transformation and thus accelerate sugar accumulation of Chinese chives. The content of total nitrogen, protein nitrogen, the activities of NR, GS and GOGAT of WB were the highest among all the treatments. The GDH activity of WB was the lowest and notably lower compared with CK. WR showed the lower contents of total nitrogen, protein nitrogen, the activities of NR and GS, and higher activities of GOGAT and GDH than those in CK, while the GDH activity of WR was the highest. WG showed lower total nitrogen, no-protein nitrogen content, and GDH activity, but higher protein nitrogen, NR and GOGAT activities than those in CK. Compared with the control, WP showed the similar results as WG, besides the higher GS activity, with most of these parameters in WP being better than in WG. These results indicated that blue, purple and green light could promote nitrogen metabolism, while red light might inhibit protein synthesis in Chinese chives. The growth of Chinese chives was much better under red and purple light, but worse under blue light, which led to thinner leaves and lower growth mass. Chinese chives of WP with the lowest crude fiber content showed the optimal comprehensive quality. Therefore, purple light exhibited the best effect on the growth of Chinese chives.