Turgor-dependent unloading of assimilates from coats of developing legume seed. Assessment of the significance of the phenomenon in the whole plant

The in vivo significance of turgor-dependent unloading was evaluated by examining assimilate transport to and within intact developing seeds of Phaseolus vulgaris (cv. Redland Pioneer) and Vicia faba (cv. Coles Prolific). The osmotic potentials of the seed apoplast were low. As a result, the osmotic gradients to the seed coat symplast were relatively small (i.e. 0.1 to 0.3 MPa). Sap concentrations of sucrose and potassium in the seed apoplast and coat symplast accounted for some 45 to 60% of the osmotic potentials of these compartments. Estimated turnover times of potassium and sucrose in the seed apoplast of < 1 h were some 5 to 13 times faster than the respective turnover times in the coat symplast pools. The small osmotic gradient between the seed apoplast and coat symplast combined with the relatively rapid turnover of solutes in the apoplast pool, confers the potential for a small change in assimilate uptake by the cotyledons to be rapidly translated into an amplified shift in the cell turgor of the seed coat. Observed adjustments in the osmotic potentials of solutions infused between the coat and cotyledons of intact seed were consistent with the in vivo operation of turgor-dependent unloading of solutes from the coat. Homeostatic regulation of turgor-dependent unloading was indicated by the maintenance of apoplast osmotic potentials of intact seeds when assimilate balance was manipulated by partial defoliation or elevating pod temperature. In contrast, osmotic potentials of the coat symplast adjusted upward to new steady values over a 2 to 4 h period. The resultant downward shift in coat cell turgor could serve to integrate phloem import into the seed coat with the new rates of efflux to the seed apoplast. Circumstantial evidence for this linkage was suggested by the approximate coincidence of the turgor changes with those in stem levels of ³²P used to monitor phloem transport. The results obtained provide qualified support for the in vivo operation of a turgor homeostat mechanism. It is proposed that the homeostat functions to integrate assimilate demand by the cotyledons with efflux from and phloem import into the coats of developing legume seed.     

田林老山中山两类森林凋落物研究

田林老山中山两类森林凋落物研究梁宏温（广西农学院林学分院,南宁５３０００１）ＳｔｕｄｉｅｓｏｎｔｈｅＬｉｔｔｅｒｆａｌｌｏｆＴｗｏＦｏｒｅｓｔＴｙｐｃｓｉｎＭｉｄ—ＡｌｔｉｔｕｄｅｏｆＬａｏｓｈａｎＭｏｕｎｔａｉｎｉｎＴｉａｎｌｉｎＣｏｕｎｔｙ．￥Ｌ...     

NMR imaging of root water distribution in intact Vicia faba L plants in elevated atmospheric CO2

The effect of elevated atmospheric CO₂ on water distribution in the intact roots of Vicia faba L. bean seedlings grown in natural soil was studied noninvasively with proton (¹H) nuclear magnetic resonance (NMR) imaging. Exposure of 24-d-old plants to atmospheric CO₂-enriched air at 650 cm³ m^?3 produced significant increases in water imaged in upper roots, hypogeal cotyledons and lower stems in response to a short-term drying-stress cycle. Above ground, drying produced negligible stem shrinkage and stomatal resistance was unchanged. In contrast, the same drying cycle caused significant depletion of water imaged in the same upper root structures in control plants subject to ambient CO₂ (350 m³ m^?3), and stem shrinkage and increased stomatal resistance. The results suggest that inhibition of transpiration caused by elevated CO₂ does not necessarily result in attenuation of water transport from lower root structures. Inhibition of water loss from upper roots and lower stem in elevated CO₂ environments may be a mitigating factor in assessing deleterious effects of greenhouse changes on crops during periods of dry climate.     

接合转移诱动系统在遗传分析和体内基因操作中的应用

接合转移诱动系统在遗传分析和体内基因操作中的应用赵巍,张成刚,蔺继尚（中国科学院沈阳应用生态研究所,１１００１５）细菌间ＤＮＡ的转移主要有转化、转导、接合和原生质体融合等几种形式。接合是通过供体菌和受体菌完整细胞间的直接接触,而传递大段ＤＮＡ的方法,...     

浙江古田山亚热带常绿阔叶林叶衰老物候影响因子研究

该文选取浙江省古田山亚热带常绿阔叶林72种木本植物,探究气候因素、系统发育关系和功能性状对亚热带常绿阔叶林叶衰老物候的影响。结果表明,叶变色期在9—12月,落叶期在10—12月。每月落叶物种数与月均温、月均降水量和月均日照时数没有显著相关性,每月叶变色物种数与月均温和月均日照时数呈弱相关;落叶性对叶变色期和落叶期具有显著影响;植物间系统发育关系对叶变色期和落叶期没有显著影响。因此,生物和非生物因子都会影响常绿阔叶树种的叶衰老,这对于提高秋季物候预测模型具有重要价值。     

中国亚热带常绿阔叶林净第一性生产力的估算

中国亚热带常绿阔叶林净第一性生产力的估算倪健（中国科学院植物研究所生态室,北京１０００９３）ＥｓｔｉｍａｔｅｏｆｔｈｅＮｅｔＰｒｉｍａｒｙＰｒｏｄｕｃｔｉｖｉｔｙｆｏｒＳｕｂｔｒｏｐｉｃａｌＥｖｅｒｇｒｅｅｎＢｒｏａｄｌｅａｖｅｄＦｏｒｅｓｔｉｎＣｈ...     

七坪林场常绿阔叶林凋落物研究初报

凋落物即来自林冠的落叶、落枝和落花果等有机残体。既是林木自身的代谢产物,又是森林土壤养分的重要来源,在森林生态系统养分循环中发挥重要的作用。有关天然林凋落物的研究,国内已有一些     

Synechococcus as an indicator of trophic status in the Cochin backwaters,west coast of India

Eutrophication is a major problem in coastal water bodies. Information about the trophic status of water bodies will enable proper management of coastal ecosystems. In this regard, biological organisms which are sensitive to environmental changes can serve as indicators of ecosystem trophic status. In this study, seasonal and spatial variations of picophytoplankton (PP; <3 μm size) community structure was assessed in the Cochin backwaters (CB) with respect to the prevailing environmental conditions during three seasons, post-monsoon (PM-I; October 2011 and PM-II; November 2012), pre-monsoon (PrM; May 2012) and monsoon (MON; August 2012). CB, along the west coast of India, receives continuous load of nutrients throughout the year through anthropogenic wastes. Trophic status index (TRIX) scores showed that CB is highly eutrophic with a high phytoplankton biomass. Synechococcus was the dominant PP observed in the study area. Seasonal and spatial salinity variations influenced the PP distribution, especially Synechococcus where PE-rich Synechococcus (SYN-PE) were dominant in higher saline (>30) and PC-rich Synechococcus (SYN-PC) in lower saline (<30) waters. SYN-PC showed a significant positive relation with chlorophyll a suggesting that this group contributes substantially to the total phytoplankton biomass. TRIX scores and SYN-PC: SYN-PE abundance ratio were negatively correlated with salinity suggesting an influence of the tidal amplitude. SYN-PC correlated positively and SYN-PE negatively with TRIX scores suggesting that these groups occupy contrasting ecological niches. These findings imply that PP distribution pattern can serve as an indicator of the trophic status of coastal water bodies.