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1.
Populations of Atriplex triangularis were grown under laboratory conditions in a growth chamber and manipulated in an inland Ohio saline pond in order to examine the relative effects of salinity, nitrogen fertilization, and population density on growth, reproduction, and survival. For laboratory plants, nitrogen fertilization was the most important variable, with biomass and reproductive effort being greatest at the high nitrogen level. As salinity increased, biomass decreased only in plants not limited by nitrogen. Increasing density caused biomass per plant to decrease at both high and low nitrogen levels. For field plants, density was the most important variable, with biomass per plant and survival both decreasing as density increased. As density increased, size inequality among individuals increased but biomass per unit area and individual reproductive effort remained relatively constant. Nitrogen fertilization slightly enhanced survival, but did not affect biomass. It is suggested that density-dependent processes may be significant even in relatively harsh physical environments.  相似文献   

2.
Buysse  Jan  Smolders  Erik  Merckx  Roel 《Plant and Soil》1993,155(1):191-194
Theoretical plant growth models postulate an important role for growth substrates such as sugars and amino acids. To test this experimentally, spinach plants were grown under controlled conditions and with nitrogen added daily, following different exponential addition schemes. Plants were harvested during exponential growth. Free amino acid levels or free sugar levels were only weakly correlated with growth and biomass partitioning. Factor analysis showed however that the product of free sugar concentration and amino acid concentration yielded a parameter adequately reflecting the plant's nutritional state.It is concluded that growth and biomass partitioning under limiting N conditions cannot be modelled solely based on N substrate levels.  相似文献   

3.
The mechanisms that allow broadly distributed aquatic plants to inhabit variable resource environments are unclear, yet understanding these mechanisms is important because broad environmental tolerance is often linked to invasiveness in terrestrial and aquatic plants. In an experimental stream, we examined the effects of different nutrient concentrations on the growth rate, biomass, and foliar nutrient concentrations of a cosmopolitan and potentially invasive aquatic plant, Nasturtium officinale (R. Br.). Nasturtium seedlings were grown under six nutrient treatment levels ranging from 0.64 μm N:0.09 μm P to 1531 μm N:204.13 μm P, for 8 weeks. Absolute and relative growth rates, and biomass of seedlings increased along a gradient of increasing nutrient concentrations but the effect of nutrient concentration was dependent on growing time. Seedling biomass varied among nutrient treatments in weeks 4 through 8 of the experiment, but did not differ in week 2. By week 8, the two highest nutrient treatments had greater biomass than the two lowest nutrient treatments. Foliar nitrogen concentration increased, whereas carbon concentration and C:N ratios decreased in response to increasing nutrients. Nasturtium grows slowly in nutrient-poor conditions but rapidly increases its growth, biomass accrual, and nitrogen storage as conditions become nutrient-rich. The response of Nasturtium to enhanced nutrient conditions may indicate how aquatic nuisance species successfully invade and dominate plant communities in streams, where resources often vary both temporally and spatially.  相似文献   

4.
Summary Two CAM plant species (Kalanchoe daigremontiana and K. tubiflora) were cultivated in pure cultures with two different levels of nitrogen and water supply. A comparison of the plant dry weight showed that the productivity was severely reduced under low nitrogen or/and water conditions. Additionally the proportion of the different organs contributing to the total biomass, and thus the ratio of root/shoot dry weight shifted substantially. At the same time the production of leaf buds in ratio to leaf biomass was increased. Concentrations of organic nitrogen and nitrate in the shoots were drastically reduced under low nitrogen or/and water conditions, but organic nitrogen concentration in the roots remained relatively high. The leaf conductance over a day was investigated only for K. daigremontiana, and decreased with reduced water and nitrogen supply. The results indicate that CAM plants do not have the predicted high nitrogen use efficiency. Under environmental stress they change from biomass production towards provisions for life preservation.  相似文献   

5.
Van Der Werf  Adrie  Enserink  Tessa  Smit  Bert  Booij  Remmie 《Plant and Soil》1993,155(1):183-186
In this paper we model allocation of carbon and nitrogen to roots and leaves as a function of the nitrogen status of a plant. Under steady-state conditions, allocation of carbon and nitrogen to leaves is exponentially (positively) correlated with plant nitrogen concentration, whereas allocation to roots is correlated negatively, also in an exponential manner.Allocation functions derived under steady-state conditions are used to simulate biomass partitioning under non-steady-state nutrient conditions. Upon nitrogen deprivation, measured and simulated values are rather similar with time, suggesting that allocation functions derived under steady-state conditions also hold under non-steady-state conditions.  相似文献   

6.
光照和氮素对喜旱莲子草形态特征和生物量分配的影响   总被引:3,自引:0,他引:3  
研究了两个光照梯度和3个土壤氮素水平交互作用对喜旱莲子草(Alternan thera philoxeroides(Mart.)Griseb.)形态特征和生物量分配的影响。结果表明,全光照促进喜旱莲子草总生物量的积累,但在遮荫条件下,喜旱莲子草可以通过增加株高、光合叶面积和改变生物量分配来适应弱光生境。土壤中氮素含量对喜旱莲子草生长有明显影响,总生物量、株高、叶面积、茎生物量比和叶生物量比等随土壤氮素水平增加而增加。光照和氮素的交互作用对总生物量、根生物量比、茎生物量比和叶生物量比也有显著影响。随着氮素水平的增高,遮荫和高光照处理下喜旱莲子草的叶面积、总生物量和叶生物量比之间的差异减小,而株高和根生物量比之间的差异增大。此外,光照强度对茎生物量比的影响具有明显的氮素浓度依赖性,低氮条件下,茎生物量比在高光照处理下显著高于遮荫处理,而在中氮条件下,遮荫处理却显著高于高光照处理,且在高氮处理下其差异进一步加大。这些结果表明喜旱莲子草在高氮素环境下能够通过形态可塑性和生物量分配模式的改变来适应弱光环境所带来的不利影响。研究结果不但可为研究喜旱莲子草对异质生境的入侵机制提供资料,也可为进一步研究喜旱莲子草的入侵和扩散与农业等生态系统中土壤氮素残留的关系提供参考。  相似文献   

7.
We isolated two bacterial strains from an experimentally lead (Pb)-polluted soil in Hungary, 10 years after soil contamination. These strains represented the two most abundant cultivable bacterial groups in such soil, and we tested their influence on Trifolium pratense L. growth and on the functioning of native mycorrhizal fungi under Pb toxicity in a second Pb-spiked soil. Our results showed that bacterial strain A enhanced plant growth, nitrogen and phosphorus accumulations, nodule formation, and mycorrhizal infection, demonstrating its plant-growth-promoting activity. In addition, strain A decreased the amount of Pb absorbed by plants, when expressed on a root weight basis, because of increased root biomass due to the production of indoleacetic acid. The positive effect of strain A was not only evident after a single inoculation but also in dual inoculation with arbuscular mycorrhizal fungi. Strain A also exhibited higher tolerance than strain B when cultivated under increasing Pb levels in the spiked soil. Molecular identification unambiguously placed strain A within the genus Brevibacillus. We showed that it is important to select the most tolerant and efficient bacterial strain for co-inoculation with arbuscular mycorrhizal fungi to promote effective symbiosis and thus stimulate plant growth under adverse environmental conditions, such as heavy-metal contamination.  相似文献   

8.
Spinach plants were grown in pots under controlled conditions in three different soils (a loamy sand, a silt loam at low mineral-N level and a silt loam at the double mineral-N level). The nitrogen uptake pattern varied considerably between the three soil types and was used to validate an equation between the relative growth rate and nitrogen content. This equation is based on the growth response of spinach plants grown hydroponically at equal environmental conditions either at optimum nitrogen supply (complete nutrient solution) or with a relative nitrate addition rate of 0.30 day–1, 0.225 day–1 or 0.15 day–1 effecting an exponential increase in nitrogen uptake. Growth in potted soil was slightly overestimated. Part of this bias was explained by the lower shoot weight ratio observed for the soil grown plants. This was demonstrated by the improvement in growth predictions when using net assimilation rate rather than relative growth rate as the driving variable in the model.  相似文献   

9.
Nicotiana tabacum is emerging as a crop of choice for production of recombinant protein pharmaceuticals. Although there is significant commercial expertise in tobacco farming, different cultivation practices are likely to be needed when the objective is to optimise protein expression, yield and extraction, rather than the traditional focus on biomass and alkaloid production. Moreover, pharmaceutical transgenic tobacco plants are likely to be grown initially within a controlled environment, the parameters for which have yet to be established. Here, the growth characteristics and functional recombinant protein yields for two separate transgenic tobacco plant lines were investigated. The impacts of temperature, day-length, compost nitrogen content, radiation and plant density were examined. Temperature was the only environmental variable to affect IgG concentration in the plants, with higher yields observed in plants grown at lower temperature. In contrast, temperature, supplementary radiation and plant density all affected the total soluble protein yield in the same plants. Transgenic plants expressing a second recombinant protein (cyanovirin-N) responded differently to IgG transgenic plants to elevated temperature, with an increase in cyanovirin-N concentration, although the effect of the environmental variables on total soluble protein yields was the same as the IgG plants. Planting density and radiation levels were important factors affecting variability of the two recombinant protein yields in transgenic plants. Phenotypic differences were observed between the two transgenic plant lines and non-transformed N. tabacum, but the effect of different growing conditions was consistent between the three lines. Temperature, day length, radiation intensity and planting density all had a significant impact on biomass production. Taken together, the data suggest that recombinant protein yield is not affected substantially by environmental factors other than growth temperature. Overall productivity is therefore correlated to biomass production, although other factors such as purification burden, extractability protein stability and quality also need to be considered in the optimal design of cultivation conditions.  相似文献   

10.
Overman AR  Scholtz RV 《PloS one》2011,6(12):e28515
The expanded growth model is developed to describe accumulation of plant biomass (Mg ha(-1)) and mineral elements (kg ha(-1)) in with calendar time (wk). Accumulation of plant biomass with calendar time occurs as a result of photosynthesis for green land-based plants. A corresponding accumulation of mineral elements such as nitrogen, phosphorus, and potassium occurs from the soil through plant roots. In this analysis, the expanded growth model is tested against high quality, published data on corn (Zea mays L.) growth. Data from a field study in South Carolina was used to evaluate the application of the model, where the planting time of April 2 in the field study maximized the capture of solar energy for biomass production. The growth model predicts a simple linear relationship between biomass yield and the growth quantifier, which is confirmed with the data. The growth quantifier incorporates the unit processes of distribution of solar energy which drives biomass accumulation by photosynthesis, partitioning of biomass between light-gathering and structural components of the plants, and an aging function. A hyperbolic relationship between plant nutrient uptake and biomass yield is assumed, and is confirmed for the mineral elements nitrogen (N), phosphorus (P), and potassium (K). It is concluded that the rate limiting process in the system is biomass accumulation by photosynthesis and that nutrient accumulation occurs in virtual equilibrium with biomass accumulation.  相似文献   

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