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    Methods for determining microalgal nutrient limitation
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    Abstract:
    The merits and methodological limitations of several main approaches for determining microalgal nutrient limitation are briefly reviewed and compared. (1) The elemental ratios of microalgae can reflect the status of nutrient limitation,but the result is far from constant and easily influenced by light,CO_(2) availability and nutrient status. (2) Enrichment experiments have been commonly used to determine the nutrient limitation in phytoplankton and natural water,but it can be influenced by the species composition of the seeding inocula phytoplankton sample and addition of one macronutrient may induce limitation of other nu trients. (3) Nutrient uptake kinetics can be used for detecting microalgal nutrient limitation, as nutrient limited cells exhibit increased uptake capacity or efficiency for the specific nutrient after it is re-supplied. But the uptake rates vary with a range of factors including microalgal species, nutrient history and nutrient status. (4) Biochemical approach has been used extensively in the study of N, P and Fe deprivation, but this method entails destruction of the sample and time consuming, and complicated process. (5) Fourier-transform infrared microspectroscopie analysis can reveal dramatic spectral differences between nutrient-limited and nutrient-replete microalgal cells and represents a novel method to investigate macromolecular synthesis in response to changes in nutrient supply. But this method has the limitation of requiring bulky and expensive equipment. (6) The chlorophyll fluorescence measurements are non-destructive and highly sensitive, thus require only small volumes and low concentration of experimental samples. These characteristics make it become an increasing potential approach for exploring nutrient status of microalgae and their physiological response to varying environmental conditions.
    The concept of nutrient use efficiency is the central to the understanding of ecosystem function. We reviewed the concept of nutrient use efficiency and resorption, its expression and calculation, affecting factors and biochemical basis, we also analyzed the current problems in the studies of nutrient use efficiency, and pointed out the directions for future research work of this field.
    Citations (5)
    Improving crop nutrient efficiency becomes an essential consideration for environmentally friendly and sustainable agriculture. Plant growth and development is dependent on 17 essential nutrient elements, among them, nitrogen (N) and phosphorus (P) are the two most important mineral nutrients. Hence it is not surprising that low N and/or low P availability in soils severely constrains crop growth and productivity, and thereby have become high priority targets for improving nutrient efficiency in crops. Root exploration largely determines the ability of plants to acquire mineral nutrients from soils. Therefore, root architecture, the 3-dimensional configuration of the plant's root system in the soil, is of great importance for improving crop nutrient efficiency. Furthermore, the symbiotic associations between host plants and arbuscular mycorrhiza fungi/rhizobial bacteria, are additional important strategies to enhance nutrient acquisition. In this review, we summarize the recent advances in the current understanding of crop species control of root architecture alterations in response to nutrient availability and root/microbe symbioses, through gene or QTL regulation, which results in enhanced nutrient acquisition.
    Nutrient cycle
    Essential nutrient
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    Quantifying nutrient limitation of primary productivity is a fundamental task of terrestrial ecosystem ecology, but in a high carbon dioxide environment it is even more critical that we understand potential nutrient constraints on plant growth. Ecologists often manipulate nutrients with fertilizer to assess nutrient limitation, yet for a variety of reasons, nutrient fertilization experiments are either impractical or incapable of resolving ecosystem responses to some global changes. The challenges of conducting large, in situ fertilization experiments are magnified in forests, especially the high‐diversity forests common throughout the lowland tropics. A number of methods, including fertilization experiments, could be seen as tools in a toolbox that ecologists may use to attempt to assess nutrient limitation, but there has been no compilation or synthetic discussion of those methods in the literature. Here, we group these methods into one of three categories (indicators of soil nutrient supply, organismal indicators of nutrient limitation, and lab‐based experiments and nutrient depletions), and discuss some of the strengths and limitations of each. Next, using a case study, we compare nutrient limitation assessed using these methods to results obtained using large‐scale fertilizations across the Hawaiian Archipelago. We then explore the application of these methods in high‐diversity tropical forests. In the end, we suggest that, although no single method is likely to predict nutrient limitation in all ecosystems and at all scales, by simultaneously utilizing a number of the methods we describe, investigators may begin to understand nutrient limitation in complex and diverse ecosystems such as tropical forests. In combination, these methods represent our best hope for understanding nutrient constraints on the global carbon cycle, especially in tropical forest ecosystems.
    Terrestrial ecosystem
    Citations (104)