Aiming at important challenges faced by Chinese agricultural production, including increased fertilizer application without yield increase, excessive soil nutrient accumulation, over-application of chemical fertilizers and declining nutrient use efficiency, this paper reviews the historical development and research advances into soil and plant nutrient management in China. It discusses the need for Chinese plant nutrition research not only to follow international cutting-edge research advances but also closely combine Chinese agricultural production practices to contribute to the sustainable development of agriculture by significantly improving both nutrient use efficiency and crop yield.

The root system plays a very important role in plant anchorage, water and nutrient uptake, as well as synthesis and storage of metabolites. Quantitative analysis of root architecture, or the spatial configuration and distribution of the root system in the soil, will facilitate our understanding of root structure, function and their interactions in the ecosystem. Here, we introduce the concepts of root architecture and summarize recent progress in quantitative analysis of root architecture, with some examples of major research methods and techniques currently being used in this area.

Arbuscular mycorrhizal (AM) symbiosis is the mutualistic association between AM fungi and most terrestrial plants: the plant roots offer carbohydrates to the fungi; in return, the fungi assist the plants with uptake of mineral nutrients, particularly phosphate, from soil, and their subsequent transfer to the root cortical cells. The formation of AM symbiosis involves complicated pathways of signal exchange and transduction, with stringent and coordinated programs. This mini-review focuses on the current knowledge in the signal transduction pathways in AM plants. Such pathways in higher plants are similar, in part, to nodulation signal pathways in legumes and are related to calcium signaling. Many detailed action models in AM signal transduction are not clear yet but may be revealed soon.

Nitrogen (N) is an essential macro-nutrient for plants. Nitrate and ammonium are the main N sources absorbed by plants. Both nitrate and ammonium transport systems can be kinetically divided into two systems: the low-affinity transport system and the high-affinity nitrate transport system. This review introduces recent advances in the physiological and molecular mechanisms of inorganic N transport in plants.

This paper summarizes the latest advances in the molecular and genetic analysis of low phosphate (Pi) responses in Arabidopsis thaliana. Emphasis is on the functional involvement of the SUMOylation pathway, several transcription factors involved in low Pi responses, Pi homeostasis regulation and Pi recycling by phospholipases in Pi-starved Arabidopsis. The potential functional relations among the genes identified so far in low-Pi responses in Arabidopsis are also discussed.

Plants play a pivotal role in the global sulfur cycle as the dominant reducer of inorganic sulfur. Inorganic sulfate in the soil is taken up by plant roots, reduced, and assimilated into cysteine, the first organic reduced sulfur, from which many critical sulfur-containing metabolites are derived and play essential roles in plant development, abiotic stress tolerance, disease and insect resistance, as well as crop yield and grain quality. Sulfur may have the most complex metabolism and regulation and serve more biological functions than any other nutrients in plants. This review summarizes the recent advances in metabolism and regulation of sulfur and its roles in stress tolerance. Important unsolved problems in sulfur metabolism and the emerging issue of sulfur

Calcium is an essential plant nutrient. Calcium deficiency may occur in acidic soils with low base saturation. Since the transpiration from enclosed tissues and fruit is low, Ca deficiency readily develops in fruit trees and vegetables with enclosed tissues or fruit. Calcium may traverse the root through an apoplastic or symplastic pathway. Calcium is also believed to be directly taken up by an actual fruit with a non-vascular bundle structure. At the molecular level, Ca enters plant cells through Ca2+-permeable ion channels in their plasma membranes, whereas low [Ca2+] in unstimulated cells is maintained by Ca2+-ATPase and Ca2+/H+ antiporters. The rapid influx of Ca2+ through cation channels in the plasma membranes, tonoplast and/or endoplasmic reticulum generates transient elevation and oscillation of [Ca2+]cyt that initiate cellular responses to a diverse range of developmental cues and environmental challenges. The cellular [Ca2+]cyt sensors include calmodulin, calcium-dependent protein kinases and calcineurin B-like proteins that allow plant cells to respond appropriately to [Ca2+]cyt signals. This article provides an overview of the mechanisms of Ca2+ transport across cellular membranes, the origins and specificity of [Ca2+]cyt signals and the characteristics of cellular [Ca2+]cyt sensors.

Iron is an essential microelement for plant growth and development. The acquisition, translocation and utilization of iron are cmplicated processes. Many genes and gene families are involved. Here, we review the progress of research into the molecular mechanisms of iron uptake and metabolism during the past 10 years and provide a molecular regulation model of iron uptake in strategy I plants.

Boron (B) is an essential mineral nutrient for higher plants. However, its physiological role in plants and its molecular mechanism are still not well understood. This paper summarizes substantial progress achieved in recent years and unresolved questions. The molecular mechanisms of B cross-linking with rhamnogalacturonan II (RG-II) to form B-RG-II complex and its important role in the development and stability of the cell wall was verified. Moreover, the enhanced formation of B-RG-II seems to be closely related to the conquering of land during plant evolution. As well, genetic engineering has confirmed that the first B transporter, BOR1, involved in xylem loading and cloned in Arabidopsis, and NIP5;1, a member of the major intrinsic protein family, function as a boric acid channel for B uptake and are crucial for plant growth and development under B limitation in Arabidopsis. Finally, some valuable germplasms for high B-utilization efficiency were screened in rapeseed, wheat, and barley, and the mapping and cloning of quantitative trait loci for tolerance to B deficiency or B toxicity are in good progress.

Zinc is an essential trace element for all organisms because it serves as a catalytic or structural cofactor for many different proteins. Organisms have evolved complicated zinc transport and regulation systems to maintain a proper intracellular concentration of zinc for normal function. In this paper, we review the transport system and gene expression regulation of zinc in both yeast and plants, and describe the quantitative trail loci of zinc.

Copper is an essential trace element for organisms. Sophisticated regulation mechanisms are involved in copper uptake, distribution, sequestration and export in yeast and plants. In this review, we focus on the current knowledge of copper transporters, metallochaperone and regulation of gene expression at the transcriptional level.