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1.
Growth and shoot: root ratio of seedlings in relation to nutrient availability   总被引:28,自引:2,他引:28  
Ericsson  Tom 《Plant and Soil》1995,168(1):205-214
The influence of mineral nutrient availability, light intensity and CO2 on growth and shoot:root ratio in young plants is reviewed. Special emphasis in this evaluation is given to data from laboratory experiments with small Betula pendula plants, in which the concept of steady-state nutrition has been applied.Three distinctly different dry matter allocation patterns were observed when growth was limited by the availability of mineral nutrients: 1, Root growth was favoured when N, P or S were the major growth constraints. 2, The opposite pattern obtained when K, Mg and Mn restricted growth. 3, Shortage of Ca, Fe and Zn had almost no effect on the shoot:root ratio. The light regime had no effect on dry matter allocation except at very low photon flux densities (< 6.5 mol m-2 day-1), in which a small decrease in the root fraction was observed. Shortage of CO2, on the other hand, strongly decreased root development, while an increase of the atmospheric CO2 concentration had no influence on dry matter partitioning. An increased allocation of dry matter to below-ground parts was associated with an increased amount of starch in the tissues. Depletion of the carbohydrate stores occurred under all conditions in which root development was inhibited. It is concluded that the internal balance between labile nitrogen and carbon in the root and the shoot system determines how dry matter is being partitioned in the plant. The consistency of this statement with literature data and existing models for shoot:root regulation is examined.  相似文献   

2.
Question: Since increases in altitude and grazing intensity generally result in decreases in height growth of alpine grasslands, plant height may integrate effects of environmental stress and grazing disturbance and provide better assessments of the variation in root: shoot (R: S) biomass ratio than other variables. However, it is unclear if there is a general relationship between plant height and R:S ratio across grassland ecosystems. Such knowledge would be helpful for root biomass estimation in grasslands. Location: An altitudinal transect in the Gonghe Basin (2880–4040 m a.s.l.), northeast Tibetan plateau. Methods: We measured standing biomass both above‐ground and below‐ground, maximum plant height (MPH) and soil variables across 43 plots. Results: Climatic variables explained the variations in MPH and R: S ratio of undegraded grasslands better than soil variables (46–50% vs < 19%), while those of degraded grasslands generally showed insignificant correlations with climatic and soil variables. There was a general relationship between R: S ratio and MPH (negative, R2= 0.76, P< 0.001) across degraded and undegraded grasslands. The relationship was used to predict R: S ratio in 13 additional plots in steppe grasslands of Inner Mongolia, and good agreement of expected and observed values has been found (R2= 0.87, P < 0.001). Conclusions: MPH, that is relatively easy to measure, can be used to predict R:S ratio at plot to regional scales. It is promising to develop a new method for large‐scale estimation of root biomass in grasslands using MPH and shoot biomass avoiding tedious procedures of physical measuring of above and below‐ground biomass.  相似文献   

3.
Summary

The seed size that is characteristic of each plant species is of central importance for their regeneration because of its effect on dispersability and seedling establishment. The chemical composition of the stored nutrients is also important in the early stages of growth. The factors that influence individual seed size and nutrient allocation during development on the parent plant are examined, and allocation strategies are compared in different plants. Experiments to determine the effective supply of different elements in seeds are reviewed. The apparent imbalance in the seed nutrient allocation is discussed. Mineral use in early seedling growth is described and the exhaustion of internal nutrient reserves is considered as a means of defining the end of seedling growth phase.  相似文献   

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In this paper I develop a null model for the expected relationship between seed mass and the mass of dispersal structure (reward) for vertebrate-dispersed plant species. The model is based on the simple assumption that the reward associated with a given seed mass is commensurate with work required to move it, and predicts that reward mass should scale relative to seed mass with an exponent of 4/3 (1.3). I tested this relationship between- and within-species of vertebrate-dispersed plants from four families from tropical rain forest in north Queensland, Australia. At a community-level there was a significant isometric relationship between log mean pulp mass and log mean seed mass across species. When family membership was considered, the estimate for the common slope between families was 1.32, surprisingly similar to the exponent predicted from commensurate reward. In addition, the 95% CI of the common slope did not include unity, providing no support for isometry. There was also no evidence that the relationships between mean log pulp mass and mean log seed mass were significantly different between families. This simple null model may be a common “rule” governing mean allocation to reward in all plant–animal dispersal mutualisms and its confirmation is the first evidence that animal dispersers have shaped the evolution of seed traits. However, I found no evidence that the scaling relationships within-species were consistently predicted by commensurate reward – a “taxon-level effect”. I suggest that the taxon-level effect arises because mean seed and mean reward mass within each species arises due to community-wide, disperser-mediated selection to produce equally attractive fruits, whereas within-species allometries may be determined by selection for fruit traits that enhance either dispersal probabilities, offspring survival or both, and these will be contingent on the environmental context into which seeds are released. G. P. Cheplick  相似文献   

7.
We investigated the response to increasing intensity of red (R) and far‐R (FR) light and to a decrease in R:FR ratio in Pinus sylvestris L. (Scots pine) seedling. The results showed that FR high‐irradiance response for hypocotyl elongation may be present in Scots pine and that this response is enhanced by increasing light intensity. However, both hypocotyl inhibition and pigment accumulation were more strongly affected by the R light compared with FR light. This is in contrast to previous reports in Arabidopsis thaliana (L.) Heynh. In the angiosperm, A. thaliana R light shows an overall milder effect on inhibition of hypocotyl elongation and on pigment biosynthesis compared with FR suggesting conifers and angiosperms respond very differently to the different light regimes. Scots pine shade avoidance syndrome with longer hypocotyls, shorter cotyledons and lower chlorophyll content in response to shade conditions resembles the response observed in A. thaliana. However, anthocyanin accumulation increased with shade in Scots pine, which again differs from what is known in angiosperms. Overall, the response of seedling development and physiology to R and FR light in Scots pine indicates that the regulatory mechanism for light response may differ between gymnosperms and angiosperms.  相似文献   

8.
温带湿地植物生物量分配格局调控群落水平养分回收效率对氮磷添加的响应 养分回收是植物养分利用策略的一个重要组成部分,但养分有效性的变化如何调控群落尺度上植物养分回收过程仍不清楚。在本研究中,我们提出两个科学问题:(1)叶片和茎养分回收过程对养分有效性增加的响应格局是不是一致?(2)群落尺度上养分富集引起的植物养分回收变化是受物种内养分回收可塑性的影响还是受物种组成变化的调控?本研究以中国东北草本植物占优势的温带湿地为研究对象,利用施肥实验调查了氮和磷添加3年后物种水平上植物地上部分生物量以及叶和茎养分回收的变化趋势,并评价了群落尺度上植物养分回收对3年养分添加的响应。对于植物叶和茎而言,氮和磷添加对养分回收效率(nutrient resorption efficiency)均没有影响,但降低了相应的养分回收度(nutrient resorption proficiency)。同样地,在群落水平上,植物氮和磷养分回收度也随着相应的养分添加而降低。而且,由于植物群落组成变化及其引起的叶茎比降低,氮添加显著降低群落尺度上植物氮和磷的养分回收效率。这些研究结果表明,温带湿地植物叶和茎养分回收过程对养分有效性增加的响应是一致的,而且养分富集引起的物种组成以及叶和茎生物量分配格局变化是驱动群落尺度上植物养分回收动态的重要因素。  相似文献   

9.
In terrestrial ecosystems, atmospheric nitrogen (N) deposition has greatly increased N availability relative to other elements, particularly phosphorus (P). Alterations in the availability of N relative to P can affect plant growth rate and functional traits, as well as resource allocation to above‐ versus belowground biomass (MA and MB). Biomass allocation among individual plants is broadly size‐dependent, and this can often be described as an allometric relationship between MA and MB, as represented by the equation , or log MA = logα + βlog MB. Here, we investigated whether the scaling exponent or regression slope may be affected by the N:P supply ratio. We hypothesized that the regression slope between MA and MB should be steeper under a high N:P supply ratio due to P limitation, and shallower under a low N:P supply ratio due to N limitation. To test these hypotheses, we experimentally altered the levels of N, P, and the N:P supply ratio (from 1.7:1 to 135:1) provided to five alpine species representing two functional groups (grasses and composite forbs) under greenhouse conditions; we then measured the effects of these treatments on plant morphology and tissue content (SLA, leaf area, and leaf and root N/P concentrations) and on the scaling relationship between MA and MB. Unbalanced N:P supply ratios generally negatively affected plant biomass, leaf area, and tissue nutrient concentration in both grasses and composite forbs. High N:P ratios increased tissue N:P ratios in both functional groups, but more in the two composite forbs than in the grasses. The positive regression slopes between log MA and log MB exhibited by plants raised under a N:P supply ratio of 135:1 were significantly steeper than those observed under the N:P ratio of 1.7:1 and 15:1. Synthesis: Plant biomass allocation is highly plastic in response to variation in the N:P supply ratio. Studies of resource allocation of individual plants should focus on the effects of nutrient ratios as well as the availability of individual elements. The two forb species were more sensitive than grasses to unbalanced N:P supplies. To evaluate the adaptive significance of this plasticity, the effects of unbalanced N:P supply ratio on individual lifetime fitness must be measured.  相似文献   

10.
Several previous studies have observed that species and individuals with large seeds respond more positively to elevated CO (2) than those with small seeds. We explored the reasons for this pattern by examining the relationship between seed size and CO (2) response in Picea abies and P. rubens using growth analysis. The large seeded species (P. abies) responded more positively to elevated CO (2) than the small seeded species (P. rubens). At the intraspecific level, P. abies individuals from large seeds responded more positively to elevated CO (2) than individuals from small seeds, however, there was no significant intraspecific variation in CO (2) response in P. rubens. The greater CO (2) response of plants from large seeds was not simply the result of a larger starting capital compounded at the same rate as in plants from small seeds. Elevated CO (2) increased relative growth rate to a greater extent in individuals from large seeds. This effect appears to be related to differences in time of establishment, source to sink ratio and nutrient availability with seed size. These results are significant not only in understanding the potential effect of rising atmospheric CO (2) concentrations on plant populations, but also in understanding the factors affecting plant success at current atmospheric CO (2) levels due to the elevation of CO (2) within the litter layer that occurs at many germination sites.  相似文献   

11.
该研究利用4个由高到低不同海拔的同质园实验,以青藏高原高寒草地优势植物垂穗披碱草(Elymus nutans)、矮嵩草(Kobresia humilis)和珠芽蓼(Polygonum viviparum)为对象,分析了植物个体根、茎、叶生物量分配及根冠比的变化规律及影响因素。结果表明:(1)植物个体根、茎、叶质量比和根冠比具有显著的种间差异;与垂穗披碱草和珠芽蓼相比,矮嵩草具有显著较高的根质量比而叶、茎质量比较低,所以其根冠比较高。(2)在向低海拔移栽的过程中,珠芽蓼叶质量比保持不变,茎质量比显著降低而根质量比显著升高,根冠比表现出显著上升的趋势;垂穗披碱草则相反,即叶、茎质量比显著升高而根质量比显著降低,根冠比表现出显著下降的趋势;矮嵩草根、茎、叶质量比和根冠比则无显著变化。(3)随着海拔降低,年均气温明显升高而年均降雨量明显降低,且在植物个体种源地和土壤基质保持一致的条件下,向低海拔移栽过程中温度是导致珠芽蓼根、茎、叶生物量分配及根冠比变化的重要因素,而水分是垂穗披碱草根、茎、叶生物量分配及根冠比变化的重要驱动因素;矮嵩草根、茎、叶生物量分配及根冠比受其遗传因素影响较大。因此,在将来暖干化的背景下,青藏高原高寒草地植物生物量的分配将会发生改变,导致它们对资源(光照、水分和土壤养分)获取和利用的变化而改变它们的种间关系,从而影响群落的物种多样性与组成,最终可能导致生态系统功能的变化。  相似文献   

12.
One of the main goals of molecular evolutionary biology is to determine the factors that influence the evolutionary rate of selectively neutral DNA, but much remains unknown, especially for plants. Key factors that could alter the mutation rate include environmental tolerances (because they reflect a plants vulnerability to changes in habitat), the pollen:ovule ratio (as it is associated with the number of mitotic divisions) and seed longevity (because this influences the number of generations per unit time in plants). This is the first study to demonstrate that seed bank persistence and drought tolerance are positively associated with molecular evolutionary rates in plants and that pollen:ovule ratio, shade tolerance and salinity tolerance have no detectable relationship. The implications of the findings to our understanding of the impact of environmental agents, the number of cell divisions and cell aging on neutral DNA sequence evolution are discussed.  相似文献   

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