The effect of LED grow light on plant senescence

Chlorophyll degradation, rapid protein loss, and RNA hydrolysis during plant senescence are mainly characterized by leaf senescence. Chloroplasts are hypersensitive to the change of surrounding light. The red light, blue light, and red-blue mixed light are conducive to the formation of chloroplasts. Blue light is helpful to increase the starch granules in chloroplasts. Red light and far-red light inhibit the development of chloroplasts. The red-blue light can boost the synthesis of chlorophyll in cucumber seedling leaves and also delay the attenuation of chlorophyll content in the later stage. This effect is more obvious with the decrease of red light ratio and the increase of blue light ratio. The chlorophyll content of cucumber seedlings under LED red-blue combined light treatment was significantly higher than monochromatic red and blue light treatment. LED blue light could significantly increase the chlorophyll a/b value of black-spotted and green garlic seedlings.

COB  LED red-blue combined plant grow light

During the leaf senescence, the content and activities of cytokinin (CTK), auxin (IAA), abscisic acid (ABA) are changed. Different light qualities have different effects on phytohormones. CTK stimulates leaf cell growth, promotes photosynthesis, inhibits the activity of ribonuclease, deoxyribonuclease and protease, and slowdowns the degradation of nucleic acids, proteins and chlorophyll, hence slowing leaf senescence. IAA is principally centered in the region where growth is strong. Violet light can increase the activity of indoleacetic oxidase, and low IAA levels prevent elongation. ABA is generally produced in senescent leaf tissues, mature fruits, seeds, stems, and roots. Compare with the white light and blue light, the red-blue LED grow light will decrease the ABA content of cucumber and cabbage to a greater extent.

Peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) are important and photoconductive protective enzymes. In the process of plant aging, the activity of these enzymes will decrease rapidly. The effects of different light qualities on the antioxidant enzyme activities of plants were significant. Illumination rapeseed seedlings for 9 days with red light, APX activity increased significantly and POD activity decreased. After 15 days of red and blue light irradiation, the POD activity of tomato was higher than that of white light 20.9% and 11.7% respectively. After 20 days of green light treatment, the POD activity was the lowest, only 55.4% of white light. For cucumber seedling leaves, blue light can obviously boot the soluble protein content and increase the activities of POD, SOD, APX, and CAT. Furthermore, the activity of SOD and APX gradually decreased with the extension of illumination time. The activity of SOD and APX under blue light and red light decreased slowly but were always higher than white light. Red light irradiation significantly reduced the activity of IAA peroxidase in tomato leaves, such as peroxidase, IAA peroxidase, and eggplant leaves, but caused the peroxidase activity of eggplant leaves to increase significantly. Therefore, the use of reasonable LED grows light strategy can effectively delay the aging of plants.