平茬高度对香椿生长及其光合特性和非结构性碳水化合物含量的影响

该研究以4年生香椿为试验材料,设置平茬20 cm(T₁)、50 cm(T₂)、80 cm(T₃)和不平茬(CK)4种处理,观测其萌枝和叶片生长情况,以及叶片的气体交换参数、光合色素含量、非结构性碳水化合物(NSC)含量的变化,分析不同平茬高度的生长生理响应差异,以明确平茬措施下香椿植株更新复壮再生的生理机制。结果表明：(1)平茬能够显著提高香椿的萌枝能力,促进侧枝和叶片生长,其萌枝数、侧枝长度在T₃处理下最高,成枝数、叶长、叶宽、叶面积及侧枝粗度在T₂处理下达到最大值。(2)随着平茬高度的增加,香椿叶片净光合速率、蒸腾速率、气孔导度和水分利用效率均先升后降,并在T₂处理达到最大,较CK分别显著提高了17.33%、10.00%、13.51%和6.98%;平茬也提高了叶片光合色素含量,叶绿素a、叶绿素b、总叶绿素含量和类胡萝卜素含量在T₂处理下分别比CK显著提高了18.34%、27.07%、21.11%和23.05%。(3)不同平茬高度处...     

不同生长期香椿叶片的抗氧化活性及其抗氧化作用分析

采用分光光度法,研究了不同生长期香椿叶片的抗氧化活性,并对其抗氧化作用进行了分析。结果表明,阴干处理对香椿总抗氧化力无显著影响,不同生长期的香椿总抗氧化力无显著差异;香椿嫩芽、嫩叶和老叶提取物均有清除.OH的作用,老叶、嫩叶对.OH的清除率均显著大于嫩芽,且阴干香椿对.OH的清除率均显著高于同一生长期的新鲜香椿,尤以阴干老叶的清除率最高;不同生长期的香椿提取物均有抑制亚油酸过氧化的作用,在低浓度时,嫩芽提取物对亚油酸过氧化的抑制率显著高于嫩叶或老叶,而在高浓度时,不同生长期香椿叶提取物对亚油酸过氧化的抑制率无显著差异。     

B9对香椿生长发育和芽萌发的影响

以不同浓度 B9溶液喷施香椿苗木 2～ 3次 ,2 5 0 0 mg· L- 1B9作用最显著 ,可使植株低矮粗壮 ,顶梢下第一复叶变长 ,增加叶片叶绿素含量 ,提高光合速率和比叶重。处理后的落叶苗木移入日光温室中 ,可明显减少休眠芽萌发所需的有效积温 ,从而利于提早上市。 B9处理后单株新芽数量、产量及芽内所含可溶性糖和粗蛋白含量增加     

香椿试管苗的生根与移栽

通过基内诱导生根、基外诱导生根及生根苗移栽等试验,研究了香椿试管苗的生根与移栽。结果表明,基内诱导生根的主要影响因子是生长素IBA,其次是培养基中无机盐浓度,适宜的生根配方是在不含无机盐的培养基中附加1.0mg/L IAB。用NAA、IAB短时间处理无根苗基部,可使部分苗生根,但生根率偏低。试管苗移栽的适宜时期为3月至7月初,以蛭石、河沙为基质效果较好。移载成活的关键是充分炼苗及良好的基质和适宜的时期,注意防虫并保温遮荫。     

毛红椿的生态地理分布及其南京引种的初步观察

通过对毛红椿生态地理分布的调查,在南京引种栽培的幼树生长规律观察及其气候适应性、土壤适应性、光能利用率、营养元素生物循环的分析,初步总结了它的生物学、生态学特性,为有效保护和开发利用这一珍贵树种提供科学依据。     

Recent CO2 rise has modified the sensitivity of tropical tree growth to rainfall and temperature

Atmospheric CO₂ (c_a) rise changes the physiology and possibly growth of tropical trees, but these effects are likely modified by climate. Such c_a × climate interactions importantly drive CO₂ fertilization effects of tropical forests predicted by global vegetation models, but have not been tested empirically. Here we use tree‐ring analyses to quantify how c_a rise has shifted the sensitivity of tree stem growth to annual fluctuations in rainfall and temperature. We hypothesized that c_a rise reduces drought sensitivity and increases temperature sensitivity of growth, by reducing transpiration and increasing leaf temperature. These responses were expected for cooler sites. At warmer sites, c_a rise may cause leaf temperatures to frequently exceed the optimum for photosynthesis, and thus induce increased drought sensitivity and stronger negative effects of temperature. We tested these hypotheses using measurements of 5,318 annual rings from 129 trees of the widely distributed (sub‐)tropical tree species, Toona ciliata. We studied growth responses during 1950–2014, a period during which c_a rose by 28%. Tree‐ring data were obtained from two cooler (mean annual temperature: 20.5–20.7°C) and two warmer (23.5–24.8°C) sites. We tested c_a × climate interactions, using mixed‐effect models of ring‐width measurements. Our statistical models revealed several significant and robust c_a × climate interactions. At cooler sites (and seasons), c_a × climate interactions showed good agreement with hypothesized growth responses of reduced drought sensitivity and increased temperature sensitivity. At warmer sites, drought sensitivity increased with increasing c_a, as predicted, and hot years caused stronger growth reduction at high c_a. Overall, c_a rise has significantly modified sensitivity of Toona stem growth to climatic variation, but these changes depended on mean climate. Our study suggests that effects of c_a rise on tropical tree growth may be more complex and less stimulatory than commonly assumed and require a better representation in global vegetation models.     

Siderin from Toona ciliata (Meliaceae) as photosystem II inhibitor on spinach thylakoids

Four natural products were isolated from plants of the Rutaceae and Meliaceae families and their effect on photosynthesis was tested. Siderin (1) inhibited both ATP synthesis and electron flow (basal, phosphorylating, and uncoupled) from water to methylviologen (MV); therefore, it acts as Hill reaction inhibitor in freshly lysed spinach thylakoids. Natural products 2-4 were inactive. Secondary metabolite 1 did not inhibit PSI electron transport. It inhibits partial reactions of PSII electron flow from water to 2,6-dichlorophenol indophenol (DCPIP), from water to sodium silicomolybdate, and partially inhibits electron flow from diphenylcarbazid (DPC) to DCPIP. These results established that the site of inhibition of 1 was at the donor and acceptor sides of PSII, between P(680) and Q(A). Chlorophyll a fluorescence measurements confirmed the behavior of the Toona ciliate coumarin 1 as P(680) to Q(A) inhibitor by the creation of silent centers. May be this is the mechanisms of action of 1 and is the way in which it develops a phytotoxic activity against photosynthesis.     

干旱胁迫对不同种源香椿叶片膜脂过氧化和保护酶系统的影响

对来源于江苏、四川、湖南、湖北、河南和陕西的香椿〔Toona sinensis(A.Juss.)Roem.〕苗进行盆栽实验,研究干旱胁迫对香椿叶片膜脂过氧化和保护酶系统的影响。结果表明,随干旱胁迫程度的加强,6个种源香椿苗叶片中的丙二醛(MDA)含量增加,超氧化物歧化酶(SOD)和过氧化物酶(POD)活性增强,但各指标的变化幅度因种源不同而异。复水后,除重度干旱胁迫造成的SOD活性变化难以恢复外,其余指标基本能恢复至对照水平。综合MDA含量及SOD和POD活性的变化情况认为,来源于河南、陕西和江苏的香椿具有较强的抗旱能力,而来源于湖北、四川和湖南的香椿抗旱能力较弱。     

中国特有濒危树种毛红椿核心和边缘居群的遗传多样性

选用8对多态的微卫星引物, 研究了毛红椿(Toona ciliata var. pubescens)核心居群和边缘居群的遗传多样性。研究结果显示, 边缘居群的观察等位基因数和有效等位基因数并不比核心居群低, 甚至更高。普通广布和稀有地方等位基因在所有居群中均有分布, 而普通地方和稀有广布等位基因分别仅在5个和3个居群中有分布。从4种类型等位基因总数上看, 边缘居群高于核心居群, 特别是边缘居群的稀有地方等位基因数量明显多于核心居群。边缘居群的平均期望杂合度和观察杂合度都高于核心居群。核心居群间的基因分化系数为0.1520, 边缘居群间为0.3045, 边缘居群与核心居群的遗传分化差异达到显著水平。核心居群间基因流大于1, 而边缘居群间基因流小于1, 说明核心居群间基因交流频繁, 边缘居群由于片段化和地形影响, 基因流较小。Mantel检验结果显示, 居群间遗传距离与地理距离的相关性不显著, 说明地理距离对毛红椿居群遗传分化的影响不显著。     

香椿嫩芽和老叶萃取物抗菌活性的比较研究

采用琼脂扩散法对香椿嫩芽和老叶萃取物的氯仿、乙酸乙酯和正丁醇萃取部分的抗菌活性进行了研究.嫩芽萃取物的抗菌活性明显高于老叶萃取物,其中嫩芽萃取物的乙酸乙酯部分表现出最强的抗菌活性,其最小抑菌浓度(MIC)为1.3 mg/mL.实验结果表明,香椿叶中的抑菌物质随着生长时间的延长而逐渐降低.