Effects of Shading on Physiological Characteristics and Ultrastructure of Mesophyll Cell of Emmenopterys henryi Leaves

doi:10.7525/j.issn.1673-5102.2020.01.006

Abstract

Abstract: We studied the effects of light on physiological characteristics and ultrastructure of mesophyll cells of Emmenopterys henryi leaves with four different light treatments:total light(L₀), transmittance 60%(L₁), transmittance 25%(L₂) and transmittance 10%(L₃). The results showed that:Shading affected the leaf water content(LWC) of and leaf morphology. With the increase of shading intensity, LWC increased, single leaf area(SLA) increased, single leaf dry weight(SLW_d) and lamina mass per unit area (LMA) decreased, and lamina area per unit mass (LAM) increased. Shading had a significant effect on photosynthesis of seedlings. The diurnal changes of both P_n and T_r showed obvious bimodal curves for L₀ and L₁, and the "noon break" appeared at 12:00, and the change of both L₂ and L₃ was relatively mild, the phenomena werenot obvious. The variation of G_s was basically consistent with that of P_n. The order of daily average of both P_n and T_r was L₁ > L₀ > L₂ > L₃. Therefore, the moderate shading is beneficial to the improvement of photosynthesis efficiency of E.henryi seedlings. Chlorophyll and carotenoid of leaves were increased under shading condition, and the contents of both chlorophyll and carotenoid were increased progressively with the increase of shading intensity. Long-term shading improved the light capture ability of leaves. Under shading condition, the change of MDA was more moderate, the activity of SOD and POD increased first and then decreased, but the MDA content under shading was always lower than that in full light. Soluble sugar showed a similar change. Under full light, the chloroplast and cell wall were distributed parallel to each other, and the thylakoid was evenly arranged, while under shading condition, the number of chloroplasts in cells increased obviously, the percentage of chloroplasts in the whole cell increased significantly, the starch granules increased, the arraying of thylakoids was close and the stacking degree increased, which improved the photosynthetic efficiency of the cells under low light. The seedlings can maintain normal physiological activities under proper shading, but the effective radiation intensity must be above 60% of natural light intensity.

Key words: Emmenopterys henryi, shading, physiological characteristics, ultrastructure

CLC Number:

Q945.79

LI Dong-Lin, JIN Ya-Qin, CUI Meng-Fan, HUANG Lin-Xi, PEI Wen-Hui. Effects of Shading on Physiological Characteristics and Ultrastructure of Mesophyll Cell of Emmenopterys henryi Leaves[J]. Bulletin of Botanical Research, 2020, 40(1): 29-40.

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