Leaf chlorosis, epinasty, carbohydrate contents and growth of tomato show different responses to the red/blue wavelength ratio under continuous light

• Published in: Plant physiology and biochemistry Vol. 141; pp. 477 - 486
• Main Authors: Pham, Minh Duy, Hwang, Hyunseung, Park, Seon Woo, Cui, Meiyan, Lee, Hyein, Chun, Changhoo
• Format: Journal Article
• Language: English
• Published: France Elsevier Masson SAS 01.08.2019
• Subjects: 3,3'-Diaminobenzidine - chemistry; Carbohydrates; Carbohydrates - chemistry; Chlorosis; Color; Continuous light; Epinasty; Fructose - chemistry; Glucose - chemistry; Hydrogen Peroxide - chemistry; Light; Lycopersicon esculentum - growth & development; Lycopersicon esculentum - radiation effects; Monochromatic light; Oxygen - chemistry; Photochemistry; Photoperiod; Photosynthesis; Plant Diseases; Plant Leaves - radiation effects; Plant Proteins - metabolism; Seedlings - metabolism; Tetrazolium Salts - chemistry; Tomato; Carbohydrates; NBT; Monochromatic light; DAB; PPF; ppi; CL; LED; Continuous light; Tomato; Chlorosis; Epinasty; EC
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2019.06.004

The induction of leaf injuries, including leaf chlorosis and epinasty, by continuous light in tomato plants is one of the most interesting and mysterious phenomena regarding plant interactions with light, the mechanism of which has not yet been revealed. To gain further insights into this particular response of tomato plants, we cultivated tomato seedlings (Solanum lycopersicum cv. Momotaro) for 14 days under continuous light with different ratios of red and blue light and compared their performance to those grown under continuous or 14/10-h photoperiodic white light using novel methods to quantitatively evaluate the level of leaf chlorosis and epinasty. Continuous monochromatic blue light induced severe chlorosis but almost completely alleviated epinasty in tomato leaf. In contrast, continuous monochromatic red light caused a lower level of leaf chlorosis but very severe epinasty. The combination of red and blue light at different ratios significantly reduced both leaf chlorosis and epinasty under continuous light condition. Carbohydrate contents showed no correlation with leaf chlorosis, while glucose and fructose contents showed correlations with the petiole and leaflet curvatures. Histochemical staining with 3,3′-diaminobenzidine and nitro blue tetrazodium chloride also did not reveal any significant buildup of hydrogen peroxide and superoxide anion in monochromatic blue light treatment. Taken together, these results suggest that chlorosis and epinasty are two distinctive leaf injuries caused by continuous light that may follow very different mechanisms, and an overaccumulation of carbohydrates in the leaf may not be the main cause of continuous light-induced leaf chlorosis in tomato. •Continuous blue light induced severe leaf chlorosis but almost no epinasty.•Continuous red light induced moderate leaf chlorosis but severe epinasty.•Red:blue ratio of 1:1 or 1:3 helped alleviate both chlorosis and epinasty.•Carbohydrate, H2O2 and O2− contents did not correlate to the severity of leaf chlorosis.