陆地棉是世界上最重要的纤维作物。株高作为植物株型的重要组成部分，影响着作物的种植模式、产量和经济系数。前期研究中，我们分离并鉴定了一个棉花HD-ZIP基因（GhHB12），该基因调控棉花的非生物和生物胁迫应答反应和生长发育过程。在本研究中，我们证明GhHB12基因受生长素诱导表达，过表达GhHB12基因能激活HY5、ATH1和HAT4基因的表达，抑制生长素的时空分布、极性运输和信号传导，并改变细胞壁扩张相关基因的表达，最终抑制棉花株高。这些结果表明，GhHB12可以通过影响生长素的信号传导和细胞壁的扩展来调节棉花株高。

A rational plant population is an important attribute to high yield of cotton, because it can provide a beneficial micro environment within the canopy for plant growth and development as well as yield formation. A 2-yr field experiment was conducted to determine the optimal plant density based on cotton yield in relation to the canopy micro environment (canopy temperature, relative humidity and light transmittance). Six plant densities (1.2-5.7 plants m-2) were arranged with a completely randomized block design. The highest cotton yield (1 507 kg ha-1) was obtained at 3.0 plants m-2 due to more bolls per unit ground area (79 bolls m-2), while the lowest yield (1 091 kg ha-1) was obtained at 1.2 plants m-2. Under the moderate plant density (3.0 plants m-2), there was a lower mean daily temperature (MDT, 27.1°C) attributing to medium daily minimum temperature (Tmin, 21.9°C) and the lowest daily maximum temperature (Tmax, 35.8°C), a moderate mean canopy light transmittance of 0.51, and lower mean daily relative humidity (MRH) of 79.7% from June to October. The results suggest that 3.0 plants m-2 would be the optimal plant density because it provides a better canopy micro environment.

N fertilization of 300 kg N ha-1 is normally applied to cotton crops in three splits: pre-plant application (PPA, 30%), first bloom application (FBA, 40%) and peak bloom application (PBA, 30%) in the Yangtze River Valley China. However, low fertilizer N plant recovery (NPR) (30-35%) causes problems such as cotton yield stagnation even in higher N rate, low profit margin of cotton production and fertilizer release to the environment. Therefore, it is questioned: Are these three splits the same significance to cotton N uptake and distribution? An outdoor pot trial was conducted with five N rates and 15N labeled urea to determine the recovery and distribution of 15N from different splits in cotton (Gossypium hirsutum L. cv. Huazamian H318) plant. The results showed that, cotton plant absorbed fertilizer 15N during the whole growing period, the majority during flowering for 18-20 d regardless of N rates (150-600 kg ha-1). Fertilizer 15N proportion to the total N accumulated in cotton plant increased with N rates, and it was the highest in reproductive organs (88% averaged across N rates) among all the plant parts. FBA had the highest NPR (70%), the lowest fertilizer N lose (FNL, 19%), and the highest contribution to the fertilizer 15N proportion to the total N (46%) in cotton plant, whereas PPA had the reverse effect. It suggests that FBA should be the most important split for N absorption and yield formation comparatively and allocating more fertilizer N for late application from PPA should improve the benefit from fertilizer.

The green-fluorescent protein (gfp) gene was evaluated as a screening marker during cotton (Gossypium hirsutum L.) transforming and plant regeneration. High expression of GFP (green-fluorescent protein) was observed in transgenic cells as early as 42 h after co-culture with Agrobacterium. Most of the stable transformation events were detected in the cells of primary vascular tissue. GFP transient expression could be detected on all the explants after co-culturing for 4 d, however, the highest GFP stable expression was recorded when the explants were co-cultured for 3 d. We believe the transient and stable expression of a foreign gene in genetic transformation were two relative but different events, because high transient expression did not surely lead to high stable transformation. Under the same conditions of in vitro culture, transgenic and non-transgenic calli exhibited different morphological characters on different stages of development. High concentration of plant growth regulators (PGRs) was efficient for somatic embryogenesis of the transgenic calli, which means that the transgenic calli need relatively higher dose of hormone for further growth and somatic embryogenesis than non-transgenic ones. Strong GFP-expression was observed in leaf, stem, petioles, floral tissues, and seedlings of T1 progeny. Segregation ratios of eight transgenic lines were scored for expression of GFP in the T1 progeny that providing further evidence of stable transformation. These results proved that GFP is a powerful reporter gene for protocol optimization, selection, and monitioring in whole transformation events.