The use of nitrogen (N) fertilizers has contributed to the production of a food supply sufficient for both animals and humans despite some negative environmental impact. Sustaining food production by increasing N use efficiency in intensive cropping systems has become a major concern for scientists, environmental groups, and agricultural policymakers worldwide. In high-yielding maize systems the major method of N loss is nitrate leaching. In this review paper, the characteristic of nitrate movement in the soil, N uptake by maize as well as the regulation of root growth by soil N availability are discussed. We suggest that an ideotype root architecture for efficient N acquisition in maize should include (i) deeper roots with high activity that are able to uptake nitrate before it moves downward into deep soil; (ii) vigorous lateral root growth under high N input conditions so as to increase spatial N availability in the soil; and (iii) strong response of lateral root growth to localized nitrogen supply so as to utilize unevenly distributed nitrate especially under limited N conditions.

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Root growth has a fundamental role in nitrogen (N) use efficiency. Nevertheless, little is known about how modern breeding progress has affected root growth and its responses to N supply. The root and shoot growth of a core set of 11 representative Chinese maize (Zea mays L.) hybrids released between 1973 and 2009 were investigated under high N (4 mmol L(-1), HN) and low N (0.04 mmol L(-1), LN) levels in a solution culture system. Compared with LN, HN treatment decreased root dry weight (RDW), the root: shoot ratio (R/S), and the relative growth rate for root dry weight (RGR(root)), but increased the total root length (TRL) and the total lateral root length (LRL). The total axial root length (ARL) per plant was reduced under HN, mostly in hybrids released before the 1990s. The number of seminal roots (SRN) was largely unaffected by different N levels. More recently released hybrids showed higher relative growth rates in the shoot under both HN and LN. However, the roots only showed increased RGR under HN treatment. Correspondingly, there was a positive linear relationship with the year of hybrid release for TRL, LRL and ARL under HN treatment. Together, these results suggest that while shoot growth of maize has improved, its root growth has only improved under high N conditions over the last 36 years of selective breeding in China. Improving root growth under LN conditions may be necessary to increase the N use efficiency of maize.

Pastoralists claim that traditional management practices involving light to moderate grazing ensure sustainable yield and promote the multifunctional services provided by rangeland ecosystems. Nectar production is a key ecosystem function crucial to successful apiculture and to the sustainability of services provided by pollinators in the Tibetan alpine rangeland.Here, we evaluated whether traditional (light to moderate) grazing promotes plant biodiversity and nectar production at the level of individual plants and at the level of an entire community. We compared plant species diversity and nectar production of the dominant nectariferous species (Saussurea nigrescens) at the individual plant level and at the community level in ungrazed, lightly grazed, moderately grazed, and heavily grazed plots in each of three Tibetan alpine meadow sites. Individual nectar production was quantified as nectar volume × floret number per capitulum × capitulum per plant. Community nectar production was calculated as individual nectar production ×the number of flowering plants per 1.0 m 2 plot. We found that nectar production at the floret, individual, and community levels was significantly higher in lightly and moderately grazed plots compared to heavily grazed or ungrazed plots. This somewhat counterintuitive observation (particularly with regard to ungrazed plots) resulted from the fact that light and moderate grazing increased floret and capitulum number, and the number of flowering individuals per plot as a result of lowered competition for light. Moreover, species richness was significantly correlated with nectar production (as a result of light to moderate grazing) both at the individual level and at the community level. These results support the traditional view that light to moderate grazing not only promotes plant biodiversity but also ensures a sustainable yield in nectar production (and forage). Thus, traditional grazing management practices are more "eco-friendly" 3 / 18 compared to recent and widespread practices involving either grazing exclusion or overgrazing in the Tibetan rangelands examined in this study.

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β-1,3-Glucanase is considered as a useful enzymatic tool for β-1,3-glucan degradation to produce (1→3)-linked β-glucan oligosaccharides with pharmacological activity properties. To validly isolate β-1,3-glucanase-producing microorganisms, the soil of Wolfiporia extensa, considered an environment rich in β-1,3-glucan-degrading microorganisms, was subjected to high throughput sequencing. The results demonstrated that the genera Streptomyces (1.90%) and Arthrobacter (0.78%) belonging to the order Actinomycetales (8.64%) in the phylum Actinobacteria (18.64%) were observed in soil for P. cocos cultivation (FTL1). Actinomycetes were considered as the candidates for isolation of glucan-degrading microorganisms. Out of 58 isolates, only 11 exhibited β-1,3-glucan-degrading activity. The isolate SYBCQL belonging to the genus Kitasatospora with β-1,3-glucan-degrading activity was found and reported for the first time and the isolate SYBC17 displayed the highest yield (1.02 U/mg) among the isolates. To check the β-1,3-glucanase contribution to β-1,3-glucan-degrading activity, two genes, 17-W and 17-Q, encoding β-1,3-glucanase in SYBC17 and one gene QLK1 in SYBCQL were cloned and expressed for verification at the molecular level. Our findings collectively showed that the isolates able to secrete β-1,3-glucanase could be obtained with the assistance of high-throughput sequencing and genes expression analysis. These methods provided technical support for isolating β-1,3-glucanase-producing microorganisms.

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