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植物叶片发育过程一般可分为原基形成、初级形态和次生形态等3个阶段[1]。在原基形成阶段,叶原基的顶端分生组织有较高浓度的生长素和细胞分裂素[2]。一般而言,新展开的叶子有较低的净光合速率与较高的暗呼吸速率和低传导的二氧化碳转移[3]。在初级形态阶段,叶片生长、细胞分裂、光合速率达到最高水平。在次生形态阶段,细胞停止增殖,叶片停止生长[4]。据报道,在番茄Solanum lycopersicum叶片成熟过程中,其总类胡萝素含量呈指数形式增加[5];在板栗Castanea millissima和紫丁香Syringa oblata叶片发育过程中,叶绿素含量也逐渐增加[6-7]。借助于光合膜的能量通量理论提出的“JIP分析法”[8],可以观察到植物叶片发育不同阶段的PSⅡ氧化还原状态和电子传递链末端电子受体间的PSⅠ受体侧的效率[9],植物叶片光合能量转换过程获得更清晰的认识。在早春期间,毛竹Phyllostachys edulis具有显著的爆发式生长特性已经获得深入研究[10-12],但是与毛竹竹秆爆发式生长相对应的叶片放叶至展叶过程中,有关光合色素、光化学效率及光合能力的变化特征尚未开展研究。为此,本研究以毛竹为研究对象,利用叶绿素荧光分析技术等,研究毛竹从叶片放叶至展叶过程中的光合色素质量分数、光合速率及光合激发能分配,试图阐明毛竹叶片发育过程中光合结构和功能的变化规律,为毛竹林的科学管理提供理论依据。
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随着毛竹叶片展开天数的增加,毛竹叶片叶绿素a,叶绿素b和类胡萝卜素质量分数不断增加(表 1)。在展叶后第15天时,毛竹叶片中的叶绿素a,叶绿素b和类胡萝卜素质量分数比第5天时分别增加了233.8%,253.8%和142.1%。在第15天后,叶绿素a,叶绿素b和类胡萝卜素基本保持不变。由此说明在叶片发育进程中,第15天时,毛竹叶发育成熟,成熟叶片的叶绿素质量分数比幼叶多。此外,说明随着毛竹叶片发育进程推进,光合色素质量分数不断增加。
表 1 毛竹发育过程中光合色素质量分数变化
Table 1. Change of the pigment content in bamboo development processes
时间/d 叶绿素a/(mg·g-1) 叶绿素b/(mg·g-1) 类胡萝卜素/(mg·g-1) 叶绿素总和/(mg·g-1) 叶绿素a/叶绿素b 5 0.65 ± 0.11 e 0.26 ± 0.11 e 0.19 ± 0.03 d 0.91 ± 0.21 d 2.68 ± 0.65 b 10 1.25 ± 0.14 d 0.41 ± 0.02 d 0.33 ± 0.06 c 1.67 ± 0.12 c 3.04 ± 0.44 a 15 1.87 ± 0.24 c 0.71 ± 0.17 c 0.46 ± 0.03 b 2.58 ± 0.40 b 2.63 ± 0.21 b 20 2.27 ± 0.37 b 0.91 ± 0.26 b 0.54 ± 0.18 a 3.18 ± 0.38 a 2.49 ± 0.67 c 25 2.52 ± 0.03 a 1.03 ± 0.11 a 0.60 ± 0.02 a 3.55 ± 0.09 a 2.48 ± 0.31 c 30 2.55 ± 0.06 a 1.05 ± 0.05 a 0.59 ± 0.03 a 3.61 ± 0.10 a 2.43 ± 0.06 c 说明:每个值均为平均值±标准误 (n=5)。根据LSD测验 (P < 0.05),不同小写字母表示叶绿素a,叶绿素b和类胡萝卜素的 -
衡量叶片光合能力的重要指标是最大净光合速率。研究表明:2年生毛竹的叶片在6个不同的发育阶段,其净光合速率都有变化(图 1)。随着毛竹叶发育进程天数的增加,净光合速率呈缓慢上升趋势,在第15天到第20天时,净光合速率达到最大值,约为9 μmol·m-2·s-1;在20 d以后的一段时间里,净光合速率呈上下波动,趋于稳定状态。表明毛竹叶在第15天到第20天之间的光合能力是最强的。
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叶片发育过程中各个时期的快速叶绿素荧光诱导动力学曲线(图 2)表明,叶片发育过程中各个时期的快速叶绿素荧光诱导动力学曲线均具有O,J,I,P相等的典型特征位点。随着叶片的发育,快速叶绿素荧光诱导动力学曲线的形状发生了变化,在初期的O相,叶片各个发育阶段的差异不明显,从J相开始,I相和P相荧光随叶片发育进程逐渐升高,叶片各个发育阶段的差异逐渐增大,在I相和P相表现出明显的差异。
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毛竹叶片发育过程中PSⅡ反应中心数和活性反应中心数变化(图 3)表明,叶片发育过程中叶片单位面积含有的PSⅡ反应中心的数量(RC/CSo)和活性反应中心数(RC/ABS)逐渐增加,发育到第15天,RC/CSo升高了14.2%;RC/ABS升高了54.4%。由此表明在叶片发育过程中,有活性的反应中心增加更快。
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毛竹叶片发育过程PSⅡ反应中心能量分配的变化(图 4)表明,在叶片发育过程中,PSⅡ单位反应中心吸收的光能(ABS/RC)和用于还原QA的能量(TRo/RC)逐渐降低,在5~15 d下降速度较快,在第15天后趋于稳定。ETo/RC数值保持平稳,表明在叶片发育过程中用于电子传递的能量变化不大。DIO/RC在5~15 d迅速减少,15 d后稳定在较低的水平,表明在叶片发育过程中单位反应中心的能量耗散越来越少,在15 d后叶片发育完成,维持较低的能量耗散。
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图 5表示毛竹叶片发育过程PSⅡ受体侧的变化。随着叶片的发育成熟,Mo不断减少说明在叶片发育过程中QA被还原的速率迅速升高,QA完全被还原所需要的能量下降。最大光化学效率(φPo)上升最少,基本稳定;φEo和ψO的变化规律一致,在5~15 d间上升较快,而在15~30 d趋于稳定,表明叶片发育过程中PSⅡ受体侧QA下游的电子传递接收的能量无论绝对值还是占总能量的比例都是不断升高的,φEo的上升表明在叶片发育过程中用于QA下游电子传递的量子不断增加,ψO的上升表明叶片发育过程中PSⅡ反应中心捕获的激子中用于QA下游电子传递的激子占捕获激子总数的比例不断增加。
Photosynthetic characteristics in the development process of Phyllostachys edulis
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摘要: 运用植物气体交换测定和叶绿素荧光测定等分析技术,测定分析毛竹Phyllostachys edulis叶片发育过程中的色素质量分数、光响应进程和叶绿素荧光参数的变化特征。结果表明:① 毛竹叶片从幼叶生长到叶片成熟的各发育阶段,叶绿素质量分数和净光合速率不断增加而趋于稳定,叶片对光能的捕获和利用能力也随之增强。② 叶片从伸出到成熟,叶片的最大光化学效率(φPo)的变化不明显。③ 毛竹叶片经放叶、展叶至第15天,PSⅡ反应中心数不断增加,其数量约升高54.4%。④ PSⅡ电子受体蛋白QA被还原的速率和还原需要的能量不断减少,用于推动QA下游电子传递的能量不断增加。因此,毛竹叶片光合功能从幼叶形成至第15天完全展叶,叶片发育趋于完善,表明毛竹叶片具备正常的光合生理功能,可以充分利用毛竹群落生境的光能资源。Abstract: Using gas exchange and chlorophyll fluorescence technologies, changes in the net photosynthetic rate, pigment content, and chlorophyll fluorescence parameters of bamboo (Phyllostachys edulis) leaves were tested. Results showed that 1) as young bamboo leaves grew to maturity, in different developmental stages, the chlorophyll content and net photosynthetic rate increased, as did the light energy capture and utilization ability. 2) From leaf out to maturity, the maximum photochemical efficiency of leaves (φPo) did not change. 3) Also, for bamboo leaves, from leaf out to 15 d, the PS Ⅱ reaction center number increased about 54.4%. 4) The rate at which the PS Ⅱ receptor side primary quinone electron acceptor (QA) decreased and the energy required for reduction continuously decreased with the energy used to drive the QA downstream electron transfer increasing. Therefore, bamboo leaf photosynthetic functions from the time the young leaves formed to after 15 d of fully expanded leaves tended to be optimal, and leaves of Ph. edulis with normal photosynthetic physiological functions could make full use of the habitat community's solar energy resources.
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表 1 毛竹发育过程中光合色素质量分数变化
Table 1. Change of the pigment content in bamboo development processes
时间/d 叶绿素a/(mg·g-1) 叶绿素b/(mg·g-1) 类胡萝卜素/(mg·g-1) 叶绿素总和/(mg·g-1) 叶绿素a/叶绿素b 5 0.65 ± 0.11 e 0.26 ± 0.11 e 0.19 ± 0.03 d 0.91 ± 0.21 d 2.68 ± 0.65 b 10 1.25 ± 0.14 d 0.41 ± 0.02 d 0.33 ± 0.06 c 1.67 ± 0.12 c 3.04 ± 0.44 a 15 1.87 ± 0.24 c 0.71 ± 0.17 c 0.46 ± 0.03 b 2.58 ± 0.40 b 2.63 ± 0.21 b 20 2.27 ± 0.37 b 0.91 ± 0.26 b 0.54 ± 0.18 a 3.18 ± 0.38 a 2.49 ± 0.67 c 25 2.52 ± 0.03 a 1.03 ± 0.11 a 0.60 ± 0.02 a 3.55 ± 0.09 a 2.48 ± 0.31 c 30 2.55 ± 0.06 a 1.05 ± 0.05 a 0.59 ± 0.03 a 3.61 ± 0.10 a 2.43 ± 0.06 c 说明:每个值均为平均值±标准误 (n=5)。根据LSD测验 (P < 0.05),不同小写字母表示叶绿素a,叶绿素b和类胡萝卜素的 -
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https://zlxb.zafu.edu.cn/article/doi/10.11833/j.issn.2095-0756.2017.03.008