High abscission rates of damaged expanding leaves: field evidence from seedlings of a Bornean rain forest tree

Herbivore damage is known to cause the premature loss of mature leaves. However, the effects of herbivory on abscission during the early stages of leaf development remain unexplored, even though herbivores frequently prefer unlignified, immature leaves. In a field experiment, we removed 50% of the tissue from leaves at various stages of development on seedlings of Shorea hopeifolia (Dipterocarpaceae), a dominant rain forest tree in Indonesian Borneo. Four weeks following simulated herbivory, >88% of unlignified expanding leaves had been abscised, compared to only 20% of fully expanded, unlignified leaves and 0% of recently lignified, mature leaves. In a separate experiment over 9 wk, simulated herbivory did not increase abscission rates of mature leaves, even when 75% of leaf tissue was removed. Because most (58%) of S. hopeifolia seedlings under natural conditions had lost 1% or less of the tissue from their mature leaves, herbivore damage probably has little effect on the abscission of mature leaves. In contrast, the tendency for damaged expanding leaves to abscise may explain why 49% of S. hopeifolia seedlings had already lost their youngest leaf. If similar patterns occur in other species, herbivore attacks on developing leaves may contribute substantially to both leaf loss and the cumulative impact of herbivory on the growth and survival of whole plants.     

Effect of lanthanum on ion absorption in cucumber seedling leaves

Scanning electron microscope and energy-dispersive X-ray analysis were used to study the tissular distributions of elements Na, Mg, Cl, K, Ca, Mn, and Fe in leaves of cucumber seedlings in the absence or presence of La³⁺. The results showed that the atomic percentages of Na, Mg, Cl, K, and Ca were basically reduced and those of Mn and Fe were increased in the presence of La³⁺; in addition, at 0.02 mM La³⁺, the reduced or increased degrees were higher than those at 2.0 mM La³⁺. The effects of La³⁺ on ion absorption were similar to those of Ca²⁺, suggesting that the rare earth element lanthanum affects the plant physiological mechanism by regulating the Ca²⁺ level in plant cell.     

The role of calcium ions in freezing injuries of winter oilseed rape leaves. Effects of calcium channel blockers and mimesis by calcium ionophore

Calcium ionophore A23187 allowing for a calcium ion influx from an apoplast to a cytoplasm, mimicked symptoms of the frost-induced injuries in winter oilseed rape leaves, as estimated by the conductivity method. Both calcium ionophore and freezing treatment induced degradation of phosphatidylcholine. On the other hand lanthanum and gadolinum ions as well as verapamil, the inhibitors of calcium ion channels, decreased the degree of the frost-induced injuries. Lanthanum ions prevented the frost-induced degradation of PC. It is proposed that freezing alters the functioning of calcium ion channels which results in calcium ion influx into a cytosol. This in turn may lead to a degradation of cell membranes.     

银杏开发造园模式的探讨

根据银杏生物学特性和生产栽培目的的不同以及目前银杏的生产状况,阐述了银杏开发的重要意义,概述了叶材兼用银杏园、果叶兼用银杏园、果材兼用银杏园的立地选择、栽培密度和抚育管理等方面的技术要求,分析了各类园的利弊,并对低效的银杏园提出了改造的建议。     

银杏无性繁殖位置效应的研究

对银杏无性繁殖的位置效应进行了研究。方差分析结果表明,位置效应在无性繁殖过程中能保持稳定,在品种之间有一定差异。随母树及接穗年龄的增长,位置效应越明显。不同无性繁殖方法有相似的位置效应,并具有显著的重现性。在自然状态下,当年生枝条生长的异质性可分为３个枝段。从嫁接到大量结实后,位置效应可经过强－弱－强阶段。采用基生复干作接穗或插条,或用修剪、复壮和扶梢等方法可以控制或消除位置效应,而且效果明显。     

悬铃木落叶的化学调控

悬铃木落叶的化学调控李恩胡晓倩王义彰朱胜东周守标（安徽师范大学生物系,芜湖２４１０００）ＣｈｅｍｉｃａｌＡｄｊｕｓｔｍｅｎｔａｎｄＣｏｎｔｒｏｌｏｆＤｅｃｉｄｕｏｕｓＬｅａｖｅｓｏｆｔｈｅＰｌａｎｅＴｒｅｅ．ＬｉＥｎ,ＨｕＸｉａｏｑｉａｎ,ＷａｎｇＹ...     

杜仲叶绿原酸的提取，分离和鉴定

杜仲叶绿原酸的提取、分离和鉴定＠戚向阳＠张声华￥华中农业大学食品科学系杜仲叶;绿原酸;提取;鉴定杜仲叶绿原酸的提取、分离和鉴定戚向阳张声华（华中农业大学食品科学系,武汉４３００７０）Ｔｈｅｅｘｔｒａｃｔｉｏｎ,ｉｓｏｌａｔｉｏｎａｎｄｉｄｅｎｔｉｆｉｃａｔ...     

箬叶多糖的分离纯化及其理化性质的研究

采用分步提取的方式从中药箬叶中分离得到８种多糖组分：酸性杂多糖ＦＳ、ＦＥ、ＦⅠ,β－Ｄ－葡萄糖醛酸聚糖ＦⅡ和四种半纤维素多糖α－Ｄ－木聚糖ＦⅢ－ａ、ＦⅢ－ｂ、ＦⅣ－ａ及ＦⅣ－ｂ．紫外光谱、红外光谱、凝胶色谱、元素分析等结果表明８种箬叶多糖为纯品．并采用纸层析,气相色谱分析确定其单糖组成．采用高效凝胶渗透色谱ＧＰＣ法测定了４种箬叶多糖ＦＥ、ＦⅠ、ＦⅢ－ａ及ＦⅣ－ａ的重均分子量Ｍｗ、数均分子量Ｍｎ,均为大分子,分子量分布较窄,纯度较高．     

Ginkgo biloba Expresses Calreticulin,the Major Calcium-Binding Reticuloplasmin in Eukaryotic Cells

Calreticulin, the main Ca²⁺ binding protein in the endoplasmic reticulum of eukaryotic cells, was characterized in Ginkgo biloba L. pollen and seeds. Electrophoretic analysis of the partly purified extracts showed the presence of two protein bands of 57 and 50kDa apparent molecular masses, which strongly cross-reacted with antibodies against plant calreticulins. Amino acid sequence comparison with other plant and animal calreticulins revealed a much higher similarity of the N-terminus of Ginkgo calreticulins with the homologue from angiosperms rather than with that from mammals. The finding of calreticulin in Ginkgo is indicative of the conservation also in gymnosperms of Ca²⁺ homeostatic mechanisms, which seem to rely on the same molecular components as all eukaryotic cells.     

菜心叶片中乙醇酸氧化酶的多种组分

乙醇酸氧化酶（EC．1．1．3．1,GO）是光呼吸中的关键酶,过去对其电泳行为和等电点的报告互不一致。Grodzinski和Col－man（1972）将菠菜、烟草等植物部分纯化的GO酶液在pH8．3的聚丙烯酰胺凝胶中电泳,活性染色后出现两条活性带,两者对FMN的依赖性有一定差异。Kerr和Groves（1975）对豌豆叶片部分纯化的GO酶液进行等电聚焦电泳,表明其pI值大于9．6.Behrends等（1982）将绿色黄瓜子叶的酶液经聚焦层析,发现GO活性分布在pH8．7附近。但Nishimura等（1983）发现在pH8．9的凝胶中南瓜子叶GO不迁移,而在pH4．5的凝胶中则出现一…