Near-UV radiation acts as a beneficial factor for physiological responses in cucumber plants

• Published in: Journal of photochemistry and photobiology. B, Biology Vol. 128; pp. 64 - 69
• Main Authors: Mitani-Sano, Makiko, Tezuka, Takafumi
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 05.11.2013
• Subjects: Cell volume; Chlorophyll - chemistry; Chlorophyll - metabolism; Chloroplasts - enzymology; Chloroplasts - metabolism; Cucumis sativus; Cucumis sativus - growth & development; Cucumis sativus - radiation effects; Glyceraldehyde-3-Phosphate Dehydrogenases - metabolism; Isocitrate Dehydrogenase - metabolism; Leaf thickness; Light; Mitochondria - enzymology; Near-UV radiation; Photosynthesis; Photosynthesis - radiation effects; Plant Leaves - chemistry; Plant Leaves - metabolism; Plant Leaves - radiation effects; Polyvinyl Chloride - chemistry; Pyridine nucleotides [nicotinamide coenzymes: NAD(H), NADP(H)]; Seedlings - physiology; Seedlings - radiation effects; Ultraviolet Rays; Leaf thickness; Cucumis sativus; Pyridine nucleotides [nicotinamide coenzymes: NAD(H), NADP(H)]; Cell volume; Photosynthesis; Near-UV radiation
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2013.07.025

•We examined the effects of near-UV radiation (300∼400 nm; wavelength) on cucumber plants.•The plants were grown under the conditions between visible lights with and without near-UV radiation.•Only visible lights without near-UV radiation suppressed the growth of the plants.•Near-UV radiation resulted in enhancement of photosynthetic, respiratory and metabolic activities.•Namely, near-UV radiation acts as a beneficial factor for physiological responses in the plants. Effects of near-UV radiation on the growth and physiological activity of cucumber plants were investigated morphologically, physiologically and biochemically using 3-week-old seedlings grown under polyvinyl chloride films featuring transmission either above 290nm or above 400nm in growth chambers. The hypocotyl length and leaf area of cucumber seedlings were reduced but the thickness of leaves was enhanced by near-UV radiation, due to increased upper/lower epidermis thickness, palisade parenchyma thickness and volume of palisade parenchyma cells. Photosynthetic and respiratory activities were also promoted by near-UV radiation, associated with general enhancement of physiological/biochemical responses. Particularly, metabolic activities in the photosynthetic system of chloroplasts and the respiratory system of mitochondria were analyzed under the conditions of visible light with and without near-UV radiation. For example, the activities of NAD(P)-dependent enzymes such as glyceraldehyde-3-phosphate dehydrogenase (G3PDH) in chloroplasts and isocitrate dehydrogenase (ICDH) in mitochondria were elevated, along with levels of pyridine nucleotides (nicotinamide coenzymes) [NAD(H) and NADP(H)] and activity of NAD kinase (NADP forming enzyme). Taken together, these data suggest that promotion of cucumber plant growth by near-UV radiation involves activation of carbon and nitrogen metabolism in plants. The findings of this research showed that near-UV radiation reaching the Earth’s surface is a beneficial factor for plant growth.