浙江天台山落叶阔叶林特征研究

天台山次生落叶阔叶林植物种类丰富 ,科属组成分散。区系成分复杂 ,从属的地理成分来看 ,温带、亚热带分布的类型居多。群落的生活型高位芽植物最多 ,地面芽植物次之。该群落叶的性质以小型叶、单叶、草质、非全缘为主。群落各样地间的相似系数除沟谷 3样地有较高的相似性外 ,其余各样地的相似系数均较低。群落物种多样性指数较高 ,各样地间多样性指数测值变幅较大。群落垂直结构复杂 ,地上成层明显。样地内多数优势种群的年龄结构为衰退型 ,群落的种类组成不稳定。乔木层中多数优势种群的分布格局呈随机分布或均匀分布 ,部分呈集群分布。     

莫斯科州针阔混交林带森林群落的灌木层结构分析

本文通过分析莫斯科州针阔混交林带１０种类型的森林群落的灌木层结构,指出森林群落中灌木层的结构（垂直结构和水平结构）特点首先取决于组成该层次的灌木种的生物学特性,此外,在不同的群落中乔木层的郁闭度、群落内生境的不一致性（如土壤的水分和肥力状况的差异）以及幼木层的盖度等在不同的程度上影响着灌木的成层和结构。分析表明,灌木在不同的针阔混交林群落中的垂直分布可归纳为三种几何类型：金字塔式、菱形式和倒三角形式。灌木的水平配置多为集团分布或随机分布,趋于集团分布。     

浙江天童森林公园植物群落演替对土壤物理性质的影响

对浙江宁波天童森林公园内的裸地、灌丛、马尾松林、马尾松木荷林、木荷林、栲树木荷林和栲树林等演替阶段土壤物理性质进行了比较分析。结果表明,尽管由于样地坡度和母质等因素的影响,演替群落土壤呈现趋砂性特征,但植物群落进展演替能明显降低土壤容重,阔叶林群落减少的幅度更显著;同时,演替能提高土壤空隙度;土壤含水量、土壤最大持水量、毛管持水量和最小持水量在演替过程中的增长趋势明显;土壤固相率减少,气相率增大。因此,植物群落进展演替能明显降低土壤紧实性,改善土壤通气性及持水性能,呈现出与土壤质地效应相反的变化趋势,促进了土壤肥力的发挥。而土壤物理性质的改善,也有利于群落物种更替和演替进程     

Effect of diethylpyrocarbonate and sodium deoxycholate on polyribosomes from cotyledons of Vicia faba

Degradation of rRNA during the isolation of polyribosomes in the presence of either sodium deoxycholate or diethylpyrocarbonate gave breakdown products with MW corresponding to 1·13, 1·02, 0·93, 0·79, 0·61, 0·52, 0·44, 0·42, 0·30, 0·28, 0·24, 0·20 and 0·12 x 10⁶ daltons.     

Effect of mineral deficiency on amine formation in higher plants

Potassium deficiency caused putrescine accumulation in the leaves of barley, radish, pea, bean and spinach plants. Magnesium deficiency caused putrescine accumulation in barley, pea and bean leaves, and also in the leaves of older radish plants. In young radish plants less putrescine was found in magnesium deficiency, and in spinach magnesium deficiency was without effect on putrescine levels. Putrescine content may be a useful guide to the mineral status of legumes, since accumulation of this amine may be detected before deficiency symptoms appear. Radioactivity from l-arginine-[U-¹⁴C] fed to barley seedlings was detected in agmatine within 2 hr, and probably also in the hordatines after 24 hr, feeding. After 2 hr the label in the agmatine was greatest in the potassium-deficient plants, but after 24 hr the level declined to that found in the agmatine of the leaves of the magnesium-deficient and control seedlings. The rate of putrescine formation was high in both potassium and magnesium deficiency. Incorporation of radioactivity in spermidine and spermine on feeding putrescine-[1,4-¹⁴C] to barley seedlings was estimated in the dansylated amines after separation by TLC. Activity was higher in spermidine and lower in spermine in the potassium-deficient plants than in the controls. The spermidine/spermine ratio declined on excision of barley leaves.     

Direct versus indirect effects of p-chloromercuribenzenesulphonic acid on sucrose uptake by plant tissues: The electrophysiological evidence

The short-term effects of p -chloromercuribenzenesulphonic acid (PCMBS) on the transmembrane potential difference (PD) of broad bean ( Vicia faba L. cv. Aguadulce) cotyledon cells and on sugar beet ( Beta vulgaris L. cv. Klein E.) leaf cells were studied by the electrophysiological method. These effects were compared with that of the permeant thiol reagents N-ethylmaleimide and HgCl₂. N-Ethylmaleimide and HgCl₂ markedly and rapidly depolarised the PD of all the material studied, while PCMBS caused either a slight depolarisation (cotyledon cells) or no depolarisation (leaf cells) during the first 30 min of treatment. In cotyledons, PCMBS markedly inhibited sucrose uptake (89%) and the sucrose-induced depolarisation associated with the proton-sucrose symport (67%), while it decreased the proton-motive force only marginally (7%). It is concluded that during short treatments (30 min or less). PCMBS inhibits sucrose uptake directly by blocking the sucrose carrier, and not the proton pump. For longer treatments, indirect effects cannot be excluded.     

青冈常绿阔叶林主要树种叶片形态生态研究

青冈常绿阔叶林主要树种叶形基本上都为椭圆形,叶面积在１５～４０ｃｍ２／叶之间,属于中型叶和小型叶;在同一植株上,青冈叶片的大小很好地符合正态分布规律,石栎则近似于负二项分布,甜槠和木荷接近正态分布;主要树种叶的大小是优势种青冈＞次优势种石栎＞其它伴生种,这在群落结构分化中具有适应意义,即其“生长策略”不同;同一树种叶片大小为中层木叶片＞上层木叶片;春夏换叶之前,叶大小和叶重达到第一高峰,秋冬季出现第二峰,叶比重为秋、冬季＞春、夏季,这是常绿植物对季节性不利气候（冬季寒冷,夏季高温伏旱）的一种生态适应。     

缙云山常绿阔叶林四川大头茶果实中矿质营养元素含量及季节动态

本文测定了缙云山常绿阔叶林中四川大头茶果实中Ｎ,Ｐ,Ｋ,Ｃａ,Ｍｇ,Ｃｕ,Ｚｎ,Ｆｅ,Ｍｎ９种矿质营养元素的含量,研究了这些元素的季节吸收特点与繁殖分配,并探讨了这些元素与某些土壤化学因素之间的关系,结果表明：四川大头茶果实在生长期内矿质营养元素含量随季节而变化,各元素平均含量顺序为：Ｎ＞Ｋ＞Ｃａ＞Ｍｇ＞Ｐ＞Ｍｎ＞Ｆｅ＞Ｚｎ＞Ｃｕ。土壤中化学因子与四川大头茶果实中常量元素含量之间的关系密切,果实中Ｎ含量受土壤中Ｎ,Ｐ,Ｋ含量的综合影响,土壤有机质最终会影响到果实中Ｎ,Ｐ,Ｋ,Ｃａ的吸收,矿质元素的果实繁殖分配量与果实净生物生产量分配之间不存在特定的比例关系。果实元素分配所占比例的大小顺序为Ｐ＞Ｎ＞Ｋ＞Ｃａ＞Ｆｅ＞Ｍｇ＞Ｍｎ＞Ｚｎ＞Ｃｕ。     

Assembly of the VirB transport complex for DNA transfer from Agrobacterium tumefaciens to plant cells

The VirB transporter is a type IV secretion system that mediates the genetic transformation of plant cells by Agrobacterium tumefaciens. Assembly of this transporter depends on, first, formation of a VirB7/B9 complex that stabilizes many of the VirB proteins, second, formation of a virulence-specific pilus composed primarily of VirB2 and VirB5, and, third, post-translational processing of VirB1 and VirB2.     

Osmotic regulation of assimilate unloading from seed coats of Vicia faba. Assimilate partitioning to and within attached seed coats.

The significance of the osmotic potential of the seed apoplast sap as a regulator of assimilate transfer to and within coats of developing seed of Vicia faba (cv. Coles Prolific) was assessed using attached empty seed coats and intact developing seed. Following surgical removal of the embryos, through windows cut in the pod walls and underlying seed coats, the resulting attached “empty” seed coats were filled with solutions of known osmotic potentials (–0. 02 versus –0. 75 MPa). Sucrose efflux from the coats was elevated at the higher osmotic potential (high osmotic concentration) for the first 190 min of exchange. Thereafter, this efflux was depressed relative to efflux from coats exposed to the low osmotic potential (high osmotic concentration) solution. This subsequent reversal in efflux was attributable to an enhanced diminution of the coat sucrose pools at the high external osmotic potential. Indeed, when expressed as a proportion of the current sucrose pool size, relative efflux remained elevated for coats exposed to the high osmotic potential solution. Measurement of potassium and sucrose fluxes to and from their respective pools in the coat tissues demonstrated that the principal, fluxes, sensitive to variative in the external osmotic potential, were phloem import into and efflux from the “empty” coats. Phloem import, consistent with a pressure-driven phloem transport mechanism, responded inversely with changes in the external osmotic potential. In contrast, sucrose and potassium efflux from the coats exhibited a positive dependence on the osmotic potential. Growth rates of whole seed were approximately doubled by enclosing selected pods in water jackets held at temperatures of 25°C. compared to 15°C. The osmotic potential of sap collected from the seed apoplast remained constant and independent of the temperature-induced changes in seed growth rates and hence phloem import. Based on these findings, it is proposed that control of phloem import by changes in the external osmotic potential observed with “empty” seed coats has no significance as a regulator of assimilate import by intact seed. Rather, maintenance of the seed apoplast osmotic potential, independent of seed growth rate, suggests that the observed osmotic regulation of efflux from the coats may play a key role in integrating assimilate demand by the embryo with phloem import.