Effects Of Light Quality On The Physiological Characteristics And Quality Of Color Sweet Pepper

Using the red (590-670 nm; peak at 640 nm), blue (420-510 nm; peak at 460 nm), red-blue (red: blue =3:1) light-emitting diode and white fluorescent as light sources, the effects of different light quality on the physiological characteristic and quality in color sweet pepper fruits were studied. The main results were as following:1. The single fruit weigh, cross diameter and vertical diameter of color sweet pepper under red light and red-blue light were higher than those under white light. Those under blue light were lowest. There was no obvious influence on L/D (vertical diameter/cross diameter) under red light and red-blue light treatment while the L/D was obviously lower under blue light than that of other treatments. The fruit is slightly flat under blue light. It is concluded blue light is not suitable for the output of color sweet pepper. Light quality had significant effects on photosynthetic characteristics of color pepper. Photosynthetic rate was highest under red light but lowest under white light. Stomatal conductance was higher under blue light and red-blue light than that under red light and white light. Evaporating rate under blue light and red-blue light was higher than those under red light and white light due to the influence of stomata conductance. Intercelluar CO₂ concentration was obviously higher under white light than those under other treatments.2. During the late growth stage of color sweet pepper, the contents of Vc under red light, blue light and red-blue light were higher than that of white light treatment. It showed that red light and blue light were all benefit to the biosynthesis of Vc. The contents of soluble sugar under red light and blue light were lower than those of red-blue light and white light treatments. It showed that the single light was not propitious to the accumulation of sugar compared with mixture light. From the overall tendency, the content of soluble protein was highest under the blue light treatment, and lowest under white light. It suggested that different light quality could promote the biosynthesis of solute protein. The effect of blue light is more obvious. The content of free amino acid was highest under blue light and lowest under red light. In the 70th day after blossoming, the content of titratable acid in Shijihong varieties ranged that: RL>BL>WL>RBL, and that of fute varieties was BL>RL>RBL>WL. It suggested that the single light increase the content of titratable acid.3. The effects of different light quality on the pigments in color sweet pepper fruits were significant. Red-blue light had the superiority in promoting degradation of chlorophyll and synthesis of carotenoid and anthocyanin while white light was worst. But white light was in favor of flavonoids biosynthesis and flavonoids biosynthesis was inhabited under red light, blue light and red-blue light in varying degree.4. The temperature has the significant influence on the physiological characteristics of color sweet pepper under the different light quality. The difference of the single fruit weight, cross diameter and vertical diameter among the treatments were significant after different temperature treatments, which ranged that: 30°C>22.5°C>15°C. It was showed that the development of color sweet pepper friut was inhabited with the temperature reduction. The lower the temperature was, the bigger the adverse effect was.The SOD activity, the contents of MDA and soluble protein under 15°C treatments were higher than those of 22.5°C and 30°C treatments. It was showed that 15°C caused the color sweet pepper hurt. Plant's protective system was activated.The contents of Vc, free amino acid and soluble suger under 15°C treatment were higher than those of 22.5°C and 30°C. On the one hand, the low temperature caused the accumulation of certain small molecular material. On the other hand, the growth of fruits was solw, which caused the accumulation of dry matter. The quality of fruits was high.