Abstract
With andromonoecious Momordica charantia L. (bitter gourd) as material, three light qualities (50 μmol·m-2·s-1) including white LED light (WL), blue monochromatic light (B, 465 nm), and red monochromatic light (R, 650 nm) were carried out to investigate their effects on seed germination, physiological and biochemical parameters, sex differentiation and photosynthetic characteristics of bitter gourd. The results showed that compared to the WL treatment, the R treatment significantly promoted seed germination, seedling height elongation and soluble sugar content, the B treatment significantly increased seedling stem diameter, reducing sugar content and soluble protein content, the R and B treatments both significantly reduced sucrose content, but their POD activity showed no significant difference. Compared with the R treatment, the B treatment significantly increased the total female flower number and female flower nod ratio in 30 nods of main stems. The study of photosynthetic characteristics found that the R and B treatments could effectively increase the stomatal conductance (GS) of leaves, significantly improved the net photosynthetic rate (Pn) compared to the WL treatment, and the effect of the B treatment was better. Compared to the R and WL treatments, the B treatment increased the maximum photosynthetic rate (Pmax), apparent quantum efficiency (AQE) and light saturation point (LSP), and reduced the dark respiration rate (Rd) and light compensation point (LCP) of the leaves. Fit light response curves showed that the adaptability and utilization of weak light in bitter gourd were middle or below, but it showed higher adaptability and utilization of strong light. Thus, it suggests that Momordica charantia is a typical sun plan with lower Rd. In summary, it is concluded that blue light has a positive effect on the seed germination, seedling growth, sex differentiation and improving the photosynthetic performance, and this will lay the foundation for artificially regulating optimum photosynthesis using specific LEDs wavelength, and help to elucidate the relationship how light quality influences the sex differentiation of plant.
Highlights
Light is a vital environmental factor regulating the growth, morphogenesis, photosynthesis, metabolism, and gene expression of plants (XU, K, et al, 2005) [1]
The R treatment significantly promoted the seed germination, the germination rate and germination potential of the seeds increased by 5.71% and 5.73% compared to the white Light-Emitting Diode (LED) light (WL) treatment
Compared to the WL and R treatments, the B treatment significantly reduced the seed germination rate and increased germination potential, and the germination rate decreased by 6.80% and the germination potential increased by 12.40% compared to the WL treatment separately
Summary
Light is a vital environmental factor regulating the growth, morphogenesis, photosynthesis, metabolism, and gene expression of plants (XU, K, et al, 2005) [1]. Plants can use light as a signal to optimize growth and development for the ambient light conditions during their whole life cycle through sensing the quality, quantity, direction and duration of the incident light, use it (Alfred, B, 1998) [2]. Many invents, such as seed germination, seedling development and induction of flowering are affected by light (Smith, T W, et al, 1986; Chory, J, et al, 1996; Chory, J, 1997) [3] [4] [5]. Blue light is more essential than red light for maintaining the activities of photosystem II and I and photosynthetic electron transport capacity in cucumber leaves (Miao, Y X, et al, 2016) [11]
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