Abstract
Shading or low light (LL) conditions are a key and necessary cultivation technique in cigar wrapper tobacco production. However, the effect of low light on the photosynthesis in cigar tobacco is not clear. Therefore, this study is designed to know the photosynthesis of cigar tobacco under different light intensities (T200, T100, and T50 μmol m−2 s−1). The results reveal that under low light, T50 especially improved the light interception and increased carbon utilization, as witnessed by a higher specific leaf area and lower specific leaf weight. Low light intensity caused better light interception and carbon utilization in cigar tobacco leaves, and thus thinner leaves are more able to use low light efficiently. The chlorophyll content is related to the photosynthesis process; thus, LL affected the photosynthesis process by lowering the chlorophyll content. Similarly, LL also altered the photosynthetic efficiency by lowering the QY_Lss, qP_Lss, and Rfd_Lss. Additionally, higher expression of Lhcb4.2, Lhcb6, PsbA, PsbB, and PsbD under low light, especially T50, shows that the PSII and antenna proteins complex efficiently utilized the absorbed energy for photosynthesis. Finally, the lower photosynthesis, particularly in T50, is attributed to the downregulation of genes related to NADPH production (petH) and the rubisco enzyme synthesis-related gene (rbcs) for CO2 fixation in the Calvin cycle. Overall, the results show that the photosynthesis is decreased under LL intensities which might be related to lower chlorophyll content and downregulation of petH and rbcs genes.
Highlights
Light is life, as it dictates the plant’s growth and development throughout its lifecycle.Light is a key regulator of various plant developmental processes, as it plays a crucial role in germination and leaf and floral development [1]
A 15% and 45% reduction is observed in T100 and T50 relative to that of T200 (Figure 2A)
The results show that Leaf area (LA) and specific leaf area (SLA) are increased, while specific leaf weight (SLW) is decreased in response to low light intensity
Summary
As it dictates the plant’s growth and development throughout its lifecycle. Light is a key regulator of various plant developmental processes, as it plays a crucial role in germination and leaf and floral development [1]. Light is the most rapidly changing factor among other environmental limitations; plants need to adjust their fitness and perform the physiological functions necessary for growth and development. Light quality and quantity both greatly influence the carbon metabolism via photosynthesis and affect other parameters related to plant growth, development, and metabolism at morpho-physiological, biochemical, and molecular levels [2]. Yang et al [3] suggest that both light quality and intensity affected plant physiology and biochemistry via changes in photosynthesis, leaf anatomy, and hormone contents.
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