Estimating mixtures of leaf functional types using continental-scale satellite and climatic data

Aim Recent research has shown that much of the variability in leaf gas exchange and leaf longevity can be related to variations in the surface : volume ratio of leaves. The aim of this paper was to develop a theoretical framework and a practical method to extend that result to the vegetation at the continental scale. Location The study was conducted in Australia. Methods We propose that vegetation is composed of a mixture of three basic leaf types, ‘turgor’ (T), ‘mesic’ (M) and ‘sclerophyll’ (S) leaves. Changes in the relative proportions of T, M and S leaves within a vegetation type are visualized using a ternary diagram and differences in vegetation structure are shown to be easily mapped onto the ternary diagram. We estimate the proportions of T, M and S leaves using readily available data. The total amount of PAR absorbed by the vegetation (fPAR) is estimated using continental‐scale satellite observations. The total fPAR is then decomposed into that absorbed by T, M and S leaves. The relative absorption of PAR by T leaves is estimated from the temporal dynamics in the satellite signal, while the relative proportions of M and S leaves are estimated using climatic (solar radiation, rainfall) data. Results When the availability of light, nutrients and water were near‐optimal, the vegetation was composed of predominantly M leaves. In low nutrient environments S leaves predominated. T leaves were dominant in disturbed environments. Conclusions The theoretical framework is used to predict that elevated atmospheric CO₂ would tend to increase the proportion of M and S leaves in an ecosystem and the resulting change means that the proportion of T leaves would decrease. In terms of the TMS scheme, this implies that elevated CO₂ has the same net effect on the vegetation as a decrease in disturbance.     

Choleretic activity and biliary elimination of lipids and bile acids induced by an artichoke leaf extract in rats

The therapeutic properties of artichoke (Cynara scolymus L.) preparations have been known since ancient times. The traditional use of artichoke leaf extract (ALE) in gastroenterology is mainly based upon its strong antidyspeptic actions which are mediated by its choleretic activity. The aim of this study was to investigate the effects of ALE on bile flow and the formation of bile compounds in anaesthetised Wistar rats after acute and repeated (twice a day for 7 consecutive days) oral administration. A significant increase in bile flow was observed after acute treatment with ALE as well as after repeated administration. The choleretic effects of ALE were similar to those of the reference compound dehydrocholic acid (DHCA). Total bile acids, cholesterol and phospholipid were determined by enzymatic assays. There was a strong ALE-induced increase in total bile acid concentration over the entire experiment. With the highest dose (400 mg/kg), a significant increase was obtained after single and repeated administration. The bile acids-increased effects of ALE were much more pronounced than those of reference (DHCA). No significant differences in cholesterol and phospholipid content could be found.     

玉米群体内太阳光辐射垂直分布规律研究

在实验观测的基础上,对玉米群体内总辐射、光合有效辐射(光量子通量)随高度以及叶面积指数的变化规律进行了分析探讨,结果显示,在玉米群体的顶部和底部,叶面积指数较小,而在中部和中上部,叶面积指数较大,在140～200 cm的高度层内,叶面积指数约占群体叶面积指数总量的53%以上.在160～180 cm的高度内叶面积指数出现峰值;太阳光辐射在玉米群体内垂直分布随高度的减小而减少,表现为“S“型变化曲线;太阳辐射透过率在不同高度层上随叶面积指数的增加而减小,表现为指数关系,即Rt=Ae -BLAI.     

Defensive role of leaf trichomes in resistance to herbivorous insects in Datura stramonium

This study assessed the role of leaf trichome density as a component of resistance to herbivores, in six populations of Datura stramonium. Phenotypic selection on plant resistance was estimated for each population. A common garden experiment was carried out to determine if population differences in leaf trichome density are genetically based. Among population differences in leaf trichome density, relative resistance and fitness were found. Leaf trichome density was strongly positively correlated to resistance across populations. In 5 out of 6 populations, trichome density was related to resistance, and positive directional selection on resistance to herbivores was detected in three populations. Differences among populations in mean leaf trichome density in the common garden suggest genetic differentiation for this character in Datura stramonium. The results are considered in the light of the adaptive role of leaf trichomes as a component of defence to herbivores, and variable selection among populations.     

小麦叶片老化期间的内肽酶与H_2O_2的关系(英文)

研究了H2 O2 和蛋白水解酶在小麦 (TriticumaestivumL .cv.Yanmai15 8)叶片老化过程中的关系。小麦叶片老化期间 ,H2 O2 含量高的叶片中内肽酶活力也高。老化后期 ,内源H2 O2 迅速累积 ,内肽酶活力迅速上升 ;通过内肽酶同工酶电泳可检测到新增一种活力较强的内肽酶。用外源H2 O2 处理全展旗叶的内肽酶粗提液 ,随着H2 O2 浓度的升高 ,内肽酶活力先上升后下降。     

Feedback regulation of constant leaf standing crop in Sasa tsuboiana grasslands

The standing crop of current leaves of Sasa tsuboiana was measured on the upper slopes of Mount Horai, Shiga prefecture, central Japan. Upper one-year-old branches in the canopy produced greater mass of current leaves than lower ones. Furthermore, culms in artificially thinned plots produced larger leaf mass per culm than those in control plots. These results reveal that leaf production is positively correlated with light intensity. Therefore, when the leaf standing crop in a given year is somewhat smaller than usual, it may increase in the following year because the branches will receive stronger light. This feedback regulation causes uniformity in the horizontal distribution of the leaf standing crop. The constancy of the leaf standing crop throughout dense stands of different heights indicates that a common equilibrium value of the leaf standing crop exists. This uniform distribution leads to an almost-uniform weak light intensity under the canopy of S. tsuboiana, and can consequently exclude other plant species.     

Involvement of the C-terminal Region in Phosphate Inhibition of Plasma Membrane Proton Pumping Activity

Received 28 August 2000/ Accepted in revised form 10 February 2001     

Photosynthesis and root growth in Spartina alterniflora in relation to root zone aeration

Spartina alterniflora Lois. is a dominant species growing in intermediate and saline marshes of the US Gulf coast and Atlantic coastal marshes. S. alterniflora plants were subjected to a range of soil redox potential (Eh) conditions representing a well aerated to reduced conditions in a rhizotron system under controlled environmental conditions. The low soil Eh resulted in inhibition of root elongation shortly after treatment initiation. Root elongation was reduced as soil Eh approached values below ca. +350 mV. Substantial decrease in root elongation was noted when soil Eh fell below +200 mV. Generally, net photosynthetic rate (PN) decreased as soil Eh was reduced, with substantial reductions in PN found when Eh approached negative values. Average PN was reduced to 87, 64, and 44% of control under +340, +245, and -180 mV treatments, respectively. The reductions in root elongation and PN in response to low soil Eh indicated the adverse effects of low soil Eh on plant functioning and the need for periods of soil aeration that allow plants to resume normal functioning. Thus periods of drainage allowing soil aeration during the growing season appear to be critical to S. alterniflora by providing favorable conditions for root growth and gas exchange with important implications for plant carbon fixation. This revised version was published online in June 2006 with corrections to the Cover Date.     

A new lycopod, Novgorodendron conophorum gen. et sp. nov., from the Lower Carboniferous of the Moscow Syneclise

A new lycopod, Novgorodendron conophorum gen. et sp. nov., is described from the Upper Visean deposits of the Kamenka River, near the town of Borovichi (Novgorod Region). The morphology of the leaf cushions of the new plant implies its intermediate position between the families Sublepidodendraceae Chaloner et Boureau and Lepidodendraceae Endlicher. The bases of the leaf cushions have peculiar conical appendages, a previously unknown morphological feature not recorded from other lycopods. We propose the term basal conical appendages for them. The interpretation of some epidermal elements in the leaf cushions of the Lepidodendraceae is revised. The structures of the leaf cushions that were previously treated as either stomata or cells with cystoliths are shown to be sunken multicellular trichomes.