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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (3): 84-92.doi: 10.11707/j.1001-7488.20150311

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Effect of Low Light Stress on Physiological Characteristics and Ultrastructure of Rhododendron hybridum Leaves

Tao Qiaojing1,2, Wu Yueyan1, Fu Tao1, Xiang Xina1,3, Li Bo2   

  1. 1. College of Biology and Environment, Zhejiang Wanli University Ningbo 315100;
    2. College of Agriculture and Biotechnology, Zhejiang University Hangzhou 310058;
    3. College of Fisheries and Life, Shanghai Ocean University Shanghai 201306
  • Received:2013-10-30 Revised:2014-12-25 Published:2015-04-10

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Abstract:

【Objective】Rhododendron hybridum is a famous ornamental species with flowers and tree crowns. The species has beautiful flowers with gorgeous flower colors, and long florescence, thus, it is a common urban afforestation tree species and indoor potted flowers. R. hybridum belongs to the weak light plant. In this study, we investigated the tolerance mechanism of Rhododendron to weak light to find the suitable light intensity for its growth, so as to provide theoretical basis for cultivation production. 【Method】A series of pot experiments were conducted to study the effects of weak light on physiological characteristics and leaves' submicroscopic structure of R. hybridum with different intensity treatments of low light (16 000,12 000,8 000,4 000 and 500 lx). 【Results】 The results indicated that in all of the treatments, the amount of leaves and blooms increased with the treatment time of days, but the amount was fewer with the decreased light intensity. The leaves gradually lost green and turned red, leaf margin became shrunk and withered with the decreased light intensity. R. hybridum grew best at the light intensity of 12 000 lx. The content of chlorophyll overall showed a rising trend when the light intensity was above 8000 lx, but gradually reduced when the light intensity was less than 8 000 lx. After 90 days, the chlorophyll contents under less than 8000 lx were significantly lower than that before the treatment(P<0.05). The photosynthetic rate of all treatments decreased significantly first, then rising, and declined subsequently, and was directly proportional to the light intensity by the end of the experiment. The malondialdehyde (MDA) contents increased fastest, and the activity of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) all decreased significantly over treatment time when the light intensity was 500 lx. From 4 000 lx to 8 000 lx light intensity, the MDA contents gradually increased but the soluble protein contents, CAT, POD and SOD activities didn't drop very much. The MDA contents increased slowest, and the decrease in soluble protein contents, CAT, POD and SOD activities was lowest from 12 000 to 16 000 lx light intensity. As the light intensity receded, the ultrastructure of R. hybridum leaves was steadily damaged: the number of chloroplasts decreased; the structure of chloroplast was seriously damaged gradually; the degree of cavity in chloroplasts increased; and the structure of cell organelles were also broken. When light was over 8 000 lx the cell structure was relatively normal. With the light intensity at 8 000 lx and lower, the chloroplast number decreased, thylakoid structure began to fuzzy, plastid balls and starch granules enlarged. Under 4 000 lx light intensity, part of chloroplast membrane was damaged, grana lamellas were blurring, plastid balls and starch granules obviously increased and enlarged. Under the light intensity of 500 lx, the cell membrane began to collapse, chloroplast membrane was heavily damaged, grana lamella disintegrated and only had a small amount of unordered lamella structure, the degree of inanition was serious, some cells even became empty cells.【Conclusion】 Based on the comprehensive analyses of various indexes, we draw a conclusion that R. hybridum is able to tolerate the low light intensity of 4 000 lx, however a suitable light intensity for R. hybridum growth is between 12 000-16 000 lx.

Key words: Rhododendron hybridum, low light stress, physiological characteristics, ultrastructure

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