Effects Of Light Environment On Growth, Yield And Physiological Metabolism Of Sweet Pepper (Capsicum Annuum L.)

Light is not only the energy of photosynthesis, but also as the form of environmental signals regulating the growth and development process of plants. The growth, fruit yield and quality of plant could be promoted by regulating the light quality reasonably. Sweet pepper (Capsicum annuum L.) is a kind of important vegetable in facility cultivation of China and the world. Carrying out the study of effects of light quality environment on growth, yield and physiological metabolism of sweet pepper has important theoretical and practical significance for guiding the regulation of facilities light quality and sweet pepper cultivation.In this paper, different colors films (purple film, blue film, red film and colorless transparent film(CK)) were used to study the microclimate of facilities, sweet pepper growth, yield and quality, and different color LED lights (white(CK), blue, red and red-blue mixed light) were used to study the effects of growth and physiological metabolism of sweet pepper seedling, in order to investigate the light requirement characteristics of sweet pepper, provide the basis for the cultivation of light environment control, and lay the foundation for the development of special film. The main results were as follows:1. Covering of different color films had changed the band of light transmittance. Purple film, blue film and red film had increased the transmission ratio in purple, blue and red sections significantly; blue film improved the violet to green light transmittance, decreased the yellow light to far-red light transmittance band; purple film improved transmittance blue and far-red light, decreased the green to orange light transmittance; red film improved the orange light to far-red light transmittance band, made the transmittance of blue and green emission reduction; the temperature and humidity under different color films, regulating intensities of light at similar level, showed no significant difference.2. Different color films were used to study effects of different light qualiy on growth, yiled and quality of sweet pepper.The result showed that:red film promoted stem growth, reduced plant height growth, blue film has the opposite trendred, purple film showed no difference with control; the flowering time of sweet pepper was delayed by covering of blue film and advanced by covering of the red film; the yield per plant and fruit number per plant of sweet pepper were the lowest in blue film and the highest in red film, but the difference was not significant with other treatments; red and purple film promoted the degradation of chlorophyll, accumulation of flavonoid and anthocyanin in colour-changed period of fruit, blue film had the opposite effect;the vitamin C and soluble protein content of sweet pepper fruit were improved by covering of blue film, soluble sugar content and free amino acids were the highest in red film.3. Different color films were used to study effects of different color films on the biomass accumulation and distribution in different organs of sweet pepper.The result showed that:red film increased dry weight of sweet pepper while blue film decreased it, it showed no difference between purple and colorless film; fruit accounted for the proportion of the dry biomass was highest under red film while the proportion of root, stem and leaf were largest under blue film; the value of root-shoot ratio was highest under blue film and lowest under red film.4. Different color films were used to study effects of different color films on photosynthesis rate and chlorophyll fluorescence parameters of sweet pepper leaves. The result showed that:compared with the colorless and transparent film, colored films increased the net photosynthetic rate, transpiration rate and stomatal conductance of sweet pepper leaves, red film was the highest; different color films had no obvious effect on the Fv/Fm and Fv/Fo value; red film and blue film improved the Fv’/Fm’ value, purple film showed no significant difference; colored films increased the PSII photochemical efficiency and blade electron transport rate (ETR), reduced the non-photochemical quenching coefficient (qN), red film had the most obvious effects.5. Different color films were used study effects of different color films on nutrient uptake and distribution of sweet pepper leaves. The result showed that:the nitrogen content in different organs of sweet pepper were the highest under blue films, phosphorus content in purple film was highest, different color films increased the potassium content in stem while showed no different of the phosphorus and potassium content in fruit; the total uptake quantity of nitrogen, phosphorus and potassium in different organs of sweet pepper were increased by red film and decreased the amount in root, leaf and fruit by blue film; blue film increased the fruit accounted for the proportion of the total uptake quantity of nitrogen, phosphorus and potassium in fruit while decreased it in leaf.6. Different LED lights, at similar light intensity (300μmol·m-2·s-1), were used to cultivate the sweet pepper seedlings. The result showed that:compared with whit light, red-blue mixed light had increased the stem diameter, dry weight, specific leaf weight and seedling index, improved chlorophyll a, xanthophyll content of leaves and root vigor, made no difference on chlorophyll b and carotene content of leaves; red light increased the plant height stem diameter and root vigor, decreased the specific leaf weight, and had little effect on pigment content of leaves; blue light made no difference on the stem diameter, dry weight, specific leaf weight and seedling index, but decreased chlorophyll, carotenoid content of leaves and root vigor.