不同氮（N）水平下玉米的生理和代谢差异是田间合理氮素营养管理的基础，对提高氮肥利用率和减少环境污染具有重要作用。本文在明确长期不同氮肥处理下玉米氮效率和产量响应的前提下，利用非靶代谢组学方法分析了相应的差异代谢物及其代谢途径的差异。结果表明，氮胁迫（包括缺乏和过量），通过调节碳代谢产物（包括糖醇和TCA循环中间体）和氮代谢产物（包含各种氨基酸及其衍生物）影响碳氮代谢的平衡。缺氮胁迫时，L-丙氨酸、L-苯丙氨酸、L-组氨酸和L-谷氨酰胺显著下调，而过量氮时，L-缬氨酸、脯氨酸和L-组氨酸显著上调。除了上述碳氮代谢中的糖醇和氨基酸外，在该实验条件下，一些次生代谢物如黄酮类化合物（包括山奈酚、木犀草素、芸香素和香叶木素）和激素类（包括吲哚乙酸、反式玉米素和茉莉酸）可以初步被筛选作为氮胁迫诊断的指标。本研究还表明，N2处理（120 kg·ha^-1 N）和N3处理（180 kg·ha^-1 N）的叶片代谢水平相似，这与12年试验中两处理之间生理指标和产量的变化趋势一致。本研究在代谢水平上验证了氮肥减施即施用量从180 kg·ha^-1（当地推荐）减少到120 kg·ha^-1的可行性，为不降低产量条件下减少氮肥施用，进而提高氮肥利用率和保护生态环境提供了理论基础。

磷（P）是一种不可再生资源，也是植物生长的关键营养元素，对作物产量的提高起着重要作用。磷肥的过量施用在农业生产中很普遍，这不仅浪费了磷肥资源，还造成了磷的积累和地下水污染。为了获得较高的产量和磷素利用效率（PUE），我们假设农业系统的表观磷平衡可以作为确定磷投入阈值的关键指标。因此，我们进行了长达12年的定位田间试验，包括6个施磷处理，施磷量分别为0、45、90、135、180和225 kg P₂O₅ ha^–1，以明确作物产量、PUE和土壤Olsen-P对磷平衡的反应并优化磷投入。结果表明，当磷肥施用量超过某一水平时，周年产量不再增加，当周年磷肥施用量为90–135 kg P₂O₅ ha^–1时可以实现较高的产量和PUE。当磷平衡阈值为2.15–4.45 kg P ha^–1时可以实现最佳产量和最小的环境风险。基于磷平衡阈值估算的磷投入为95.7–101 kg P₂O₅ ha^–1，施磷量在此阈值内时可以协同提高产量与PUE（90.0–94.9%）。此外，本研究发现磷投入-产出平衡框架的建立有助于评估土壤Olsen-P在未来的变化，其中土壤磷平衡每增加100 kg P ha^–1，有效磷含量上升4.07 mg kg^–1。总之，磷平衡可以作为农业生产中磷管理的一个重要指标，为限制磷过剩和制定更高产、高效和环保的磷肥管理策略提供有力参考。

Gossypium hirsutum races are believed to be potential reservoirs of desirable traits, which can play crucial roles to overcome the existing narrow genetic base of modern Upland cotton cultivars.  However, prior to utilizing the races in cotton improvement programs, understanding their genetic constitutions is needed.  Thus, this study used molecular and morphological techniques to characterize 110 G. hirsutum germplasm including 109 semi-wild accessions and one Upland cotton cultivar, CRI12.  In the study, 104 SSR markers detected 795 alleles, with an average of 7.64 alleles per marker, ranging from 3 to 14, and average polymorphism information content (PIC) value of 0.71.  And 96 of the markers were found to be highly informative, with PIC value≥0.50.  Pairwise genetic similarity coefficient across the accessions ranged from 0.19 to 1.00, with an average value of 0.46.  Morphological characterization was done using fiber length, fiber strength, micronaire, fiber uniformity index, and fiber elongation.  Pairwise taxonomic distance within the accessions ranged from 0.17 to 3.41, with a mean of 1.33.  The SSR and fiber quality traits data set based unweighted pair group method of arithmetic mean (UPGMA) analysis grouped the accessions into 7 and 12 distinct clusters, respectively, that corresponds well with the results of principal component analysis (PCA).  Our study revealed the existence of vast molecular and morphological diversities within the accessions and provided valuable information on each semi-wild accession for quick and better informed germplasm utilization in cotton breeding programs.   

Telomeres form the ends of eukaryotic chromosomes and serve as protective caps that keep chromosomes structure independency and completeness. The first plant telomere DNA was isolated from Arabidopsis thaliana and was shown to have tandemly repeated sequence 5´-TTTAGGG-3´. The Arabidopsis-type telomere has been found in many plants, but several reports indicate that this sequence is absent in some plants. Up to now, no research has been conducted on the telomere of cotton. In this paper, the Arabidopsis-type telomere sequence was amplified and cloned using the primers designed based on the fragment containing telomere sequence in an Arabidopsis bacterial artificial chromosome (BAC). Fluorescence in situ hybridization (FISH) with cotton metaphase chromosomes using the Arabidopsis-type telomere sequence as probes indicated that the signals were located at all chromosome ends of seven diploid and two tetraploid cotton species with different signal intensities among chromosome complements of different cotton species, even between long and short arms of the same chromosome. To identify the signals of FISH, the genome DNA of Xinhai 7, a cultivar of Gossypium barbadense, digested by BAL-31 nuclease was introduced in this study. The result of BAL-31 digestion indicated that the hybridization signals of FISH represent the outermost DNA sequence of each cotton chromosomes. So we first proved that the telomeric repeats of cotton cross-hybridize with that of Arabidopsis. The results of terminal restriction fragment (TRF) showed significant variation in telomere length among cotton species. The telomere length of cultivated cotton was close to 20 kb and was larger than those of wild cotton species whose telomere length ranged from 6 to 20 kb.