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Summary Which factors cause fast-growing plant species to achieve a higher relative growth rate than slow-growing ones? To answer this question 24 wild species were grown from seed in a growth chamber under conditions of optimal nutrient supply and a growth analysis was carried out. Mean relative growth rate, corrected for possible ontogenetic drift, ranged from 113 to 356 mg g–1 day–1. Net assimilation rate, the increase in plant dry weight per unit leaf area and unit time, varied two-fold between species but no correlation with relative growth rate was found. The correlation between leaf area ratio, the ratio between total leaf area and total plant weight, and relative growth rate was very high. This positive correlation was mainly due to the specific leaf area, the ratio between leaf area and leaf weight, and to a lesser extent caused by the leaf weight ratio, the fraction of plant biomass allocated to the leaves. Differences in relative growth rate under conditions of optimum nutrient supply were correlated with the soil fertility in the natural habitat of these species. It is postulated that natural selection in a nutrient-rich environment has favoured species with a high specific leaf area and a high leaf weight ratio, and consequently a high leaf area ratio, whereas selection in nutrient-poor habitats has led to species with an inherently low specific leaf area and a higher fraction of root mass, and thus a low leaf area ratio.  相似文献
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 比较研究了紫茎泽兰(Ageratina adenophora)和飞机草(Chromolaena odorata)的形态、生物量分配、生长和光合特性对氮营养的可塑性反应,探讨其与入侵性 的关系。结果表明:1) 两种入侵植物对氮营养变化表现出很高的可塑性。随供氮量的增加,两种植物的根冠比、根生物量比降低,叶生物量比(LMR)、叶面积比和叶根比升高。 低氮时,增加吸收器官的生物量分配,有利于养分吸收;高氮时,更多的生物量投入同化器官, 有利于碳积累。相比之下紫茎泽兰对氮素的适应性更强。2) 两种入侵植物偏好较高的氮营养环境,土壤氮含量升高利于紫茎泽兰和飞机草的入侵。在较大的氮范围内,其相对生长速 率(RGR)、总生物量、株高、分枝数、叶面积指数、最大净光合速率和光合色素含量都随供氮量的增加而显著增加,过量氮素对上述参数的抑制不显著。在本地种基本停止生长的干季,紫茎泽兰和飞机草仍维持较高的RGR,这与它们的入侵性密切相关。3) 在决定RGR对氮营养的响应过程中,平均叶面积比和净同化速率同等重要。LMR对两种植物的RGR有重要的影响,是决定处理间和种间RGR差异的重要因素。随氮素的增加,紫茎泽兰的比叶面积(SL A)降低,飞机草的SLA升高,但在所有氮水平下,前者的SLA都高于后者,紫茎泽兰SLA的变化规律更利于植物适应氮环境。  相似文献
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Theory for growth of plants derived from the nitrogen productivity concept   总被引:19,自引:0,他引:19  
A theory is developed on the assumption that growth of plants is determined by the current amount of nitrogen in the plants. The nitrogen-growth relation is formalized in the nitrogen productivity concept (amount of biomass produced per amount of nitrogen in the biomass and per unit of time), which is essentially a constant for a given species under fixed environmental conditions. A number of results follow for increases in whole plant biomass: (A) The relative growth rate is a linear function of the internal nitrogen concentration. (B) The maximal relative growth rate uniquely determines the scaling of the time axis. (C) Exponential growth is consistent only with stable internal nitrogen concentration. Dose-response curves expressed in reduced variables (the ratio between a variable and the same variable for a plant growing under optimal conditions) are universal, so that all species and all environmental conditions yield the same curve. This is confirmed by experimental data. The shape (linear, exponential, etc.) of the nitrogen uptake curve is the only parameter differentiating these universal curves. The Mitscherlich curve or variations of it can be fitted very closely to the derived dose-response curves, except under exponential growth. A conclusion drawn from the analysis is that the results of nutrition experiments cannot be properly interpreted unless the variation with time of the amount of nitrogen in the plant is known. The theory can be extended to more complex situations, for example, time-varying environmental conditions.  相似文献
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Theories and methods on plant nutrition and growth   总被引:18,自引:0,他引:18  
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研究了不同遮光处理对西葫芦幼苗形态及光合生理特性的影响.结果表明,在60%透光率条件下,西葫芦幼苗具有较高的相对生长率、净光合速率、气孔导度、蒸腾速率、单叶水分利用效率、饱和蒸汽压、表观量子效率和叶绿素含量,而胞间CO2浓度较低;西葫芦幼苗具有较高的光饱和点(1 125 μmol·m-2·s-1)、较低的光补偿点(15.2 μmol·m-2·s-1).弱光下西葫芦幼苗较耐低浓度CO2,而强光下的幼苗较耐高浓度CO2.60%透光率下西葫芦幼苗叶片丙二醛和脯氨酸含量最低,而过氧化物酶和过氧化氢酶活性则最高.  相似文献
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