Although light is essential to photosynthesis, few studies have examined the effects of different LED spectra on photosynthate distribution in potato plants. Therefore, we exposed tuberising potato plants to white (W), red (R), blue (B) and green (G) LED treatments and compared tuber development and carbohydrate partitioning among the plants. R-treated plants had greater photosynthetic leaf area during tuber development compared with those under other treatments, thus enhancing assimilation. Although R-treated plants had higher 13C assimilation in the leaves, stems and roots than those under B treatment, there was no difference in partitioning of 13C assimilation and yield in the tubers of each plant between R and B treatments. For the tuber size, R-treated plants had a higher ratio of large tubers (>20 g) and a lower ratio of small (2–20 g) and medium-sized (10–20 g) tubers than those under W. B-treated plants had more medium-sized and large tubers than those under W. The reason may be that plants under R treatment distributed more assimilated 13C in their first tuber than those under other treatments. By contrast, plants under B balanced photosynthate distribution among their tubers. Leaves under G treatment had lower photosynthetic efficiency and ΦPSII than those under W, R or B treatment, which resulted in lower 13C photosynthate allocation in organs and lower tuber yield per plant than in R and B treatments. Overall, R treatment promoted 13C assimilation and led to more large tubers than other treatments. B-treated plants distributed more photosynthates into tubers rather than other organs and showed balanced tuber development.
Under different red (R):blue (B) photon flux ratios, the growth performance of rapeseed (Brassica napus L.) is significantly different. Rapeseed under high R ratios shows shade response, while under high B ratios it shows sun-type morphology. Rapeseed under monochromatic red or blue light is seriously stressed. Transcriptomic and proteomic methods were used to analyze the metabolic pathway change of rapeseed (cv. "Zhongshuang 11") leaves under different R:B photon flux ratios (including 100R:0B%, 75R:25B%, 25R:75B%, and 0R:100B%), based on digital gene expression (DGE) and two-dimensional gel electrophoresis (2-DE). For DGE analysis, 2054 differentially expressed transcripts (|log(fold change)|≥1, q<0.005) were detected among the treatments. High R ratios (100R:0B% and 75R:25B%) enhanced the expression of cellular structural components, mainly the cell wall and cell membrane. These components participated in plant epidermis development and anatomical structure morphogenesis. This might be related to the shade response induced by red light. High B ratios (25R:75B% and 0R:100B%) promoted the expression of chloroplast-related components, which might be involved in the formation of sun-type chloroplast induced by blue light. For 2-DE analysis, 37 protein spots showed more than a 2-fold difference in expression among the treatments. Monochromatic light (ML; 100R:0B% and 0R:100B%) stimulated accumulation of proteins associated with antioxidation, photosystem II (PSII), DNA and ribosome repairs, while compound light (CL; 75R:25B% and 25R:75B%) accelerated accumulation of proteins associated with carbohydrate, nucleic acid, amino acid, vitamin, and xanthophyll metabolisms. These findings can be useful in understanding the response mechanisms of rapeseed leaves to different R:B photon flux ratios.
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