遮光对连香树幼苗光合特性及其叶片解剖结构的影响
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引用本文:李冬林,金雅琴,崔梦凡,王 火,江 浩,祝亚云.遮光对连香树幼苗光合特性及其叶片解剖结构的影响[J].西北植物学报,2019,39(6):1053~1063
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作者单位
李冬林1,金雅琴2,崔梦凡2,王 火1,江 浩1,祝亚云1 (1 江苏省林业科学研究院南京2111532 金陵科技学院 园艺学院南京210038) 
基金项目:江苏省重点研发计划(现代农业)项目(BE2017387)
中文摘要:以2年生连香树实生苗为材料,在田间通过黑色遮阳网设置全光照(L0)及透光率55%(L1)、25%(L2)和10%(L3)4种光环境,研究遮光对连香树幼苗光合作用及叶片解剖结构的影响。结果表明:(1)连香树幼苗叶片Pn在全光和L1处理下呈非典型的“乁”形变化,未出现“午休”现象,中午14:00出现极值,而在L2和L3处理下变化相对缓和,极值出现在中午12:00;叶片Gs呈现与Pn类似的变化趋势,而Ci则呈基本一致的凹形变化。(2)各处理PnGsTr的日均值均表现为L0>L1>L2>L3,而Ci的日均值则呈相反的顺序;PnGsTr、气温和光合有效辐射均呈极显著正相关关系(P<0.01)。(3)全光照连香树幼苗的光补偿点(LCP)、光饱和点(LSP)、暗呼吸速率(Rd)均显著高于遮光处理,并维持较高的Pn而未出现明显的光抑制;遮光导致幼苗的LCP、LSP、Rd显著降低,有利于充分利用弱光,以满足低光环境下植株的正常生长。(4)与全光照相比,遮光下连香树叶片气孔密度显著变小,但气孔器长度、气孔器宽度、单个气孔器面积显著增加,气孔器面积百分比减少,影响幼苗细胞内外的水分和气体传递。(5)遮光条件下,连香树叶片明显变薄,表皮细胞厚度减小,栅栏组织(PT)厚度降低,排列变得疏松,海绵组织(ST)厚度增加,PT/ST相应减小。(6)与全光照相比,强度遮光下(L2和L3)连香树幼苗生长受阻,苗高(H)和基径(D)明显减小,生物量模型D2H下降;而轻度遮光(L1)下幼苗H和D、H/D和D2H均未出现显著变化。研究发现,连香树具有一定的光忍耐性和喜光性,对光照条件的生态幅较宽,轻度遮光影响较小,但强度遮光对连香树幼苗气体交换参数和光合响应特征产生了显著影响,同时影响了叶片的解剖结构和气孔分布特征,从而影响连香树幼苗的生长形态。在育苗生产中,适度遮光有利于降低气温、减小蒸腾,但遮光后田间有效辐射强度应保持在自然光强的55%以上。
中文关键词:遮光  连香树  光合特性  叶片解剖结构  生长
 
Photosynthetic Characteristics and Leaf Anatomical Structure of Cercidiphyllum japonicum Seedlings under Shading Condition
Abstract:Effects of shading on photosynthesis characteristics and leaf anatomical structure of Cercidiphyllum japonicum seedlings were researched. Four shade treatments including full sunlight (L0), 55% sunlight (L1), 25% sunlight (L2) and 10% sunlight (L3) were set. The results showed that: (1) shading had an significant effect on daily variation characteristics of photosynthesis of seedlings. The changes of Pn under L1 treatment were similar to L0, and showed rough “乁” shape, and the “noon break” did not appear in the course of the day, and the peak value appeared at 14:00 AM, that of other treatments was relatively mild, and the peak value appeared at 12:00 AM. The variation curve of Gs similar to Pn, and Ci showed the basically concave change. (2) The order of daily average of Pn, Gs and Tr was L0 > L1 > L2 > L3, and the order of Ci was versa. Correlation analysis showed that Pn was positively correlated with Gs, Tr, Ta and photosynthetically active radiation (PAR) (P < 0.01). (3) The photosynthesis light response characteristics under different treatments were obviously different. Under full sunlight, the light compensation point (LCP), light saturation point (LSP) and dark respiration rate (Rd) of seedlings were significantly higher than that under shading. The seedlings can maintain high Pn without obvious light inhibition, and C. japonicum seedlings had the ability of light tolerance in a certain degree, and showed the property of light demander. Shading resulted in a significant decrease of LCP, LSP and Rd, which was conducive to the growth of seedings under low light conditions. (4) Shading significantly affected the stomatal distribution on leaf surface. Under shading treatments, the stomatal density was smaller compared with the control, but the length of stomata, width of stomata and single stomatal area increased significantly. The percentage of stomatal area reduced, which will affect water and gas delivery between inside and outside of the seedling cells. (5) Under shading, the leaf thickness decreased, the upper epidermis thickened and the lower epidermis thinned. The thickness of palisade tissue (PT) decreased, sponge tissue (ST) was increased, and the PT/ST decreased accordingly. (6) Shading affects the growth form of C. japonicum seedlings. Compared with the control, the seedlings growth were inhibited under intensive shading(L2 and L3), the height(H) and basal diameter(D) decreased, and D2H dwindled accordingly, while the mild shading (L1) had no significant effects on H, D, H/D and D2H of seedlings. So the ecological width of C. japonicum seedlings to the light was wide. In forest seedlings production, moderate shading is beneficial to reduce air temperature and reduce transpiration, but the PAR in the field should be kept above 55% of natural light intensity.
keywords:shading  Cercidiphyllum japonicum  photosynthetic characteristics  leaf anatomical structure  growth
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