Abstract
Alteration of ploidy in one particular plant species often influences their environmental adaptation. Warm-season bermudagrass is widely used as forage, turfgrass, and ground-cover plant for ecological remediation, but exhibits low shade tolerance. Adaptive responses to shade stress between triploid hybrid bermudagrass cultivars [“Tifdwarf” (TD), “Tifsport” (TS), and “Tifway” (TW)] and tetraploid common bermudagrass cultivar “Chuanxi” (CX) were studied based on changes in phenotype, photosynthesis, and secondary metabolites in leaves and stems. Shade stress (250 luminance, 30 days) significantly decreased stem diameter and stem internode length, but did not affect the leaf width of four cultivars. Leaf length of CX, TD, or TW showed no change in response to shade stress, whereas shade stress significantly elongated the leaf length of TS. The CX and the TS exhibited significantly higher total chlorophyll (Chl), Chl a, carotenoid contents, photosynthetic parameters [PSII photochemical efficiency (Fv/Fm), transpiration rate, and stomatal conductance] in leaves than the TW and the TD under shade stress. The CX also showed a significantly higher performance index on absorption basis (PIABS) in leaf and net photosynthetic rate (Pn) in leaf and stem than the other three cultivars under shade stress. In addition, the TS maintained higher proantho cyanidims content than the TW and the TD after 30 days of shade stress. Current results showed that tetraploid CX exhibited significantly higher shade tolerance than triploid TD, TS, and TW mainly by maintaining higher effective photosynthetic leaf area, photosynthetic performance of PSI and PSII (Pn and Fv/Fm), and photosynthetic pigments as well as lower Chl a/b ratio for absorption, transformation, and efficient use of light energy under shade stress. For differential responses to shade stress among three triploid cultivars, an increase in leaf length and maintenance of higher Fv/Fm, gas exchange, water use efficiency, carotenoid, and proanthocyanidin contents in leaves could be better morphological and physiological adaptations of TS to shade than other hybrid cultivars (TD and TW).
Highlights
Light is an indispensable ecological factor for plant growth and development
There was no significant difference in Leaf length (LL) among Tifdwarf ” (TD), TW, TS, and CX under shade stress (Figure 1B)
The decrement of stem diameter (SD) and stem internode length (SIL) was significant in all cultivars in response to shade stress (Figures 1D,E)
Summary
Light is an indispensable ecological factor for plant growth and development. Weak or intense light affects plant morphogenesis and photosynthesis depending on different species, such as C3 and C4 plants. Net photosynthetic rate (Pn) always decreases with increasing shade, especially in C4 plants (Kubásek et al, 2013; Xie et al, 2020). The shade affects other photosynthetic characteristics, such as inconsistent light saturation and compensation points, as well as declines in non-photochemical burst capacity and electron transfer rate (Huang et al, 2011; Kim et al, 2011). In addition to physiological changes including declines in photosynthesis, transpiration rate (Tr), and carbohydrate accumulation, shade induces morphological alterations, as demonstrated by thinner leaves and stems, longer leaves and internodes, lower shoot density, and more upright growth (Fankhauser and Batschauer, 2016). Horticultural plants including various flowers, ornamental grasses, and turfgrasses often suffer from more shade situations than trees since they have a lower ecological niche (Pires et al, 2011; Fan et al, 2019). The breeding and application of shade-enduring plants are of great significance to agriculture and horticulture
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