Effects of LED Grow Lights with Different Light Quality on Plant Growth Quality

Effects of Led Grow Lights with Different Light Quality on Plant Growth Quality

Led Plant Light quality has a great influence on plant growth and development, photosynthetic characteristics, yield and quality. Studies have shown that Horticultural LED Lights green light and red light can obviously promote the elongation of the stems of colored bell pepper seedlings, blue light has a dwarfing effect on seedlings, compound light has a better effect than monochromatic light, and it is significantly longer under green light. Red light is not conducive to the increase of chrysanthemum stems.

The stem length of red light treatment is 43.0% less than that of the control; there are also reports that red light is beneficial to the thickening of chrysanthemum plants. Increasing the proportion of blue light can effectively reduce the plant height of cucumber seedlings, and increasing the proportion of red light can make the products of photosynthesis more transported to the leaves of seedlings.

Chlorophyll a, chlorophyll b, and carotenoids of lettuce all increase with the proportion of blue light. After treatment with blue light or increasing the proportion of blue light, the chlorophyll content of the plant was significantly increased and the photosynthetic rate of the plant was significantly increased. It indicates that the higher blue light intensity ratio may be beneficial to the synthesis of photosynthetic pigments.

The photosynthesis of 7% blue light plants in the red and blue combined light can work normally; as the proportion of blue light increases, the photosynthetic capacity of the leaves also increases, but after the blue light ratio exceeds 50%, the photosynthetic capacity of the leaves will decrease. Under the single red light quality, the plants accumulated more dry matter, the internodes were longer, the stem thickness was smaller, the leaves were small, and the total sugar content was high. The plants under the single blue light quality had less dry matter accumulation.

The internodes are shorter and the stems are thicker, which inhibits the elongation and growth of the stems to a certain extent. The leaves of cucumber seedlings treated with red light had the highest soluble sugar content, and those treated with blue light had the highest soluble protein content. Compared with the control, there were significant differences.

The chlorophyll content of tomato seedlings under red light treatment increased, the stomatal conductance and transpiration rate increased, and the photosynthetic rate was significantly higher than that of other treatments; the chlorophyll content of blue light treatment was slightly lower, but the photosynthetic rate was still significantly higher than that of the control.

The open stomata increased the intercellular CO2 concentration in the leaves. The increase in stomatal conductance of plant leaves was specifically induced by blue light.

For most plants, Plant Grow Lights red light promotes the increase in leaf area. Under the red light treatment, the leaves of radish seedlings, toon seedlings, tomatoes, cucumber seedlings, tobacco, grass poison and lettuce expanded faster, and the leaves were larger. Similarly, blue light can increase the area of the leaves, but blue light inhibits the expansion of the leaves of tobacco, poinsettia, and clover. Adding blue light to red light can significantly increase the leaf area of lettuce.

Under the red, blue and yellow light treatment, the spinach leaf area was significantly larger than other treatments.

Red light treatment is conducive to the accumulation of dry matter in crops such as tomato, eggplant, cucumber, lettuce and other crops. The red and blue composite light promotes the increase of biomass of peppers, phalaenopsis, verbena, and cucumber. Adding green, yellow, purple and white lights to the combination of red and blue light has a significant effect on the biomass of lettuce, cherry tomatoes and non-heading cabbage.

Red light is beneficial to the accumulation of carbohydrates in plants. Red light treatment can significantly increase the soluble sugar content of spinach, cucumber, pepper, tomato seedlings and radish sprouts. Red light can promote the accumulation of starch, which has been reported on crops such as soybean, cotton, oil sunflower sprouts and rapeseed. Because the output of photosynthetic products in the leaves can be suppressed by red light, so that starch accumulates in the leaves. The change of soluble protein content in leaves is one of the reliable indicators reflecting the physiological function of leaves. Blue light is good for protein synthesis. Blue light promotes the soluble protein content of pea seedlings, lettuce, cucumbers and sprouts. Blue light significantly promotes the increase of total amino acid and sugar content of chrysanthemum leaves.

The current research found that blue light can obviously promote the dark breathing of mitochondria, and the organic acid produced during the breathing process can be used as a carbon frame for the synthesis of amino acids, which is beneficial to protein synthesis.

The compound spectrum also has different promoting effects on plant photosynthetic products. Yellow Light is beneficial to the synthesis of soluble sugar and protein in lettuce, the formation of sucrose content in tomato and the accumulation of free amino acids in rape sprouts. The combination of low-dose UV-B and red light significantly increased the accumulation of sugar content in tomatoes. Blue light and UV-A can promote the synthesis of cucumber fruit protein.

The combination of blue and red light promotes the accumulation of soluble and soluble proteins. Red, blue and white composite light promotes the synthesis of soluble sugar and nitrogen content. The total starch content of tomato seedlings treated with the combination of red, blue and green light was the highest. SOD, as an endogenous active oxygen scavenger for plants, can maintain high activity under adversity to effectively remove active oxygen and keep it at a low level, thereby reducing its damage to membrane structure and function.

The study found that the color sweet pepper seedlings had the highest SOD activity under green light, and the difference between blue light and red light was not significant; POD is an active oxygen scavenger. The increase in its activity can reduce the damage of active oxygen to the membrane, and the lowest POD activity under green light; CAT can scavenge free radicals and maintain the integrity of the membrane system to reduce the harmful effects of adverse environments on plants.

White light has the highest CAT activity, blue light has the second highest, green light has a higher CAT activity, and yellow light and red light have this enzyme activity similar. Violet and blue light can delay the degradation of chlorophyll and soluble protein and membrane peroxidation by increasing the activity of CAT and other antioxidant enzymes in cucumber seedlings and their gene expression, thereby playing a role in alleviating the senescence of plants.

Red light and blue light are the main light sources absorbed by plants, and also the signal light sources of plants' main photoreceptors. Under low light conditions, LED red and blue light sources can effectively control the growth of cucumber seedlings, improve the quality of seedlings, and alleviate the physiological stress damage under low light. Red and blue compound light promoted the accumulation of biomass of pepper, rice five-leaf seedlings and lettuce plants. The red-blue combined light source with 60% blue light may be a relatively good light source for cherry tomato fruits.

The leaf area value of tomato seedlings under red / blue (2: 1) fill light condition is the largest, but the leaf area value under red / blue (7: 1) Grow Light condition is relatively small in the red-blue composite light, indicating red light The increase in proportion can only promote leaf growth within a certain range. Red light is beneficial to the radial growth of oilseed rape stems and leaves. Properly increasing the proportion of blue light is conducive to the horizontal growth of stems and leaves, root development and photosynthetic pigment synthesis.

Vegetables grow, increasing biomass and nutrient content. Weak light conditions will reduce the soluble protein content of cucumber seedlings. After red and blue light supplementation, the soluble protein has a significant increase. The content of soluble sugar and soluble protein in leaves of tomato seedlings under red / blue (2: 1) supplementary light reached maximum. LED mixed red and blue light sources treat gourd and pumpkin seedlings with well-developed root systems, high dry matter content, increased seedling index, and improved seedling quality; the increase of blue light components in red and blue mixed LEDs inhibits the growth of seedling stems and promotes seedling stems Thick increase.

The cotyledon area, soluble sugar, starch, carbohydrate, sucrose and C / N of lettuce seedlings under red and blue light were the largest and significantly higher than that of red light, indicating that adding an appropriate amount of blue light to red light is more conducive to carbohydrate accumulation in lettuce seedlings. The 25% and 50% blue light treatment is beneficial to the accumulation of lettuce biomass. It has a large photosynthetic pigment content, a large leaf area, and a thick leaf, which is good for photosynthesis. At the same time, the root system is well developed and the activity is strong, which is good for nutrients. With moisture absorption, the growth is better than other treatments.

The chlorophyll content is greatly affected by the R / B ratio, and blue light significantly reduces the chlorophyll content in strawberry leaves. 660nm red light and 450nm blue light can regulate the lettuce chlorophyll content. With the increase of blue light and the decrease of red light, the content of chlorophyll a and b gradually decreases.

The net photosynthetic rate and stomatal conductance of cucumber seedlings treated with red and blue combination were the largest, while the net photosynthetic rate, stomatal conductance and transpiration rate of single red and blue light were smaller, but the intercellular CO2 concentration was higher. Proper increase of blue light can improve the antioxidant enzyme activity of tomato seedlings.

With the increase of the proportion of red light, the activities of antioxidant enzymes such as SOD and CAT increase first and then decrease. Under R / B (2: 1) supplementary light The SOD activity decreased.

Most studies have shown that blue light can reduce the fresh and dry weight of plants. With the increase of the proportion of blue light, the lettuce dry weight and fresh weight changes tend to increase first and then decrease. At different growth stages, blue light has different effects on the biomass of Wutacai, but the increase in biomass in the early growth period is inversely proportional to the red / blue value, and in the later growth period is proportional to the red / blue value. Blue-violet light has an inhibitory effect on stem elongation. Compared with white light, blue-violet light significantly reduced the ginger plant height and increased its stem thickness. In terms of the effect of light quality on the root system, some studies have shown that the oat plants treated with blue light and purple light have more roots and developed root systems.

The study found that the combination of red / blue (1: 1) can significantly improve the growth and quality of lettuce; red / blue (7: 3) is the most suitable light quality condition for cucumber seedling growth, and the maximum photosynthetic rate can reach monochromatic red 4 times under the light. When the red / blue ratio is 8: 1, lettuce shows obvious photosynthetic advantages. Adding yellow light on the basis of red and blue compound light is beneficial to the synthesis of spinach photosynthetic pigments, and significantly promotes the growth of spinach. Adding yellow light and purple light can improve the photosynthetic potential of cherry tomato seedlings, and can alleviate the red and blue weak light stress.