施氮量与播种期对棉花产量和品质及棉铃对位叶光合产物的影响

【目的】本研究旨在揭示施氮量调控不同播种期棉铃对位叶光合产物形成与运转的生理机制,以期为棉花的合理氮肥运筹提供理论依据。【方法】试验于2005和2007年在中国农业科学院棉花研究所(河南安阳,黄河流域黄淮棉区)进行,以科棉1号和美棉33B品种为材料,设置大田不同播种期(4月25日和5月25日)和不同施氮量[低氮N 0 kg/hm2(N0)、适氮N 240 kg/hm2(N240)、高氮N 480 kg/hm2(N480)]处理,研究施氮量对不同播种期棉花产量和品质及棉铃对位叶光合产物的影响。【结果】1)4月25日播种条件下,随施氮量的增加棉铃对位叶中蔗糖含量先升高后降低,淀粉含量增加;随播种期的推迟,N240、N480处理下的棉铃对位叶蔗糖和淀粉含量差异不明显,但均显著高于N0处理;花后24~45 d,棉铃对位叶中蔗糖含量与叶氮浓度呈显著正相关,且相关系数随花后天数的增加而降低;花后17~24 d,蔗糖转化量与叶氮浓度呈显著负相关,至花后31~52 d,反而呈显著正相关(P0.01)。表明棉铃对位叶中适宜叶氮浓度有利于碳水化合物的累积。2)4月25日播种条件下,N0、N480处理对棉花单株铃数、铃重和皮棉产量影响为负效应,对纤维长度和麦克隆值影响较小;晚播低温条件下,N480处理的棉花铃重、皮棉产量、纤维比强度均有所提高,麦克隆值得以优化。因此,施氮量与播种期对纤维比强度和麦克隆值的影响存在补偿效应,晚播棉花增加施氮量可减小因低温而造成的纤维比强度降低的幅度,优化麦克隆值。【结论】本试验条件下,播种期(温度)和施氮量对棉铃对位叶光合产物含量、棉花产量和品质存在互作效应,其主导因素是播种期(温度),施氮量对其有补偿效应。随播种期的推迟,施氮量N 240 kg/hm2时棉花单铃重、产量及纤维品质降低的主要原因是晚播低温使棉铃对位叶中的光合产物(蔗糖和淀粉含量)增加,抑制了光合产物向棉铃及纤维的运输。晚播低温条件下,适量追施氮肥可调节棉铃对位叶中的氮浓度并提高光合产物再利用的能力,促进棉花单铃的形成,降低棉纤维比强度的下降幅度,优化麦克隆值。     

施氮量对不同开花期棉（Gossypium hirsutum L.）铃纤维细度和成熟度形成的影响

为兼顾试验的重复性和生态区域性,选用高品质棉（科棉1号）和常规棉（美棉33B）品种为材料,于2005年分别在江苏南京（118o50E, 32o02N,长江流域下游棉区）和江苏徐州（11711E, 3415N,黄河流域黄淮棉区）设置施氮量（低氮:N 0 kg/hm2;适氮:N 240 kg/hm2;高氮:N 480 kg/hm2）试验,研究施氮量对不同开花期棉铃纤维细度、成熟度和马克隆值形成的影响。结果表明:（1）施氮量显著影响棉纤维细度、成熟度和马克隆值的形成过程,但三者在不同开花期对氮素水平的响应不同,施氮量与开花期对棉纤维细度、成熟度和马克隆值的形成存在互作效应。8月10日前开花的棉铃,铃期［花后0～50 d （DPA）］日均温在23.3 oC以上,纤维细度、马克隆值以N 0 kg/hm2施氮量下最大,棉纤维马克隆值与纤维细度的相关性较大;8月25日开花的棉铃（铃期日均温在20.8～23.3 oC之间）,纤维成熟度、马克隆值以N 240 kg/hm2施氮量下最大;9月10日开花棉铃（铃期日均温低于20.8 oC）,纤维细度、成熟度和马克隆值均以N 480 kg/hm2最大,棉纤维马克隆值与纤维成熟度的相关性增强。（2）影响不同开花期间纤维细度、成熟度和马克隆值的主要因素是铃期日均温,最终纤维细度、成熟度和马克隆值在不同施氮量之间的变异与不同开花期（铃期日均温不同）间的变异比较,前者显著小于后者。综上,因开花期不同而形成的铃期日均温是决定细度、成熟度和马克隆值的最重要因素,施氮量可通过对位叶叶氮浓度NA影响棉纤维细度、成熟度和马克隆值的形成过程,增加施氮量可减小上述指标在不同开花期间的差异。     

秸秆投放、矿物氮施用及翻耕措施对玉米(Zea mays L.)和棉花(Gossypium hirsutum L.)秸秆分解的影响

With the present understanding that decomposing straw may not only affect soil properties,but possibly greenhouse gas emissions as well,focus among cnvironmental researchers has gradually expanded to include understanding of decomposition rate and stability of straw of different plants in different soils under different management conditions.Against such a background,a short-term(60 days)greenhouse simulation experiment was carried out to study the effects of straw placement,external mineral N source and tillage on straw decomposition of maize and cotton in two contrasting soils,a red soil(Ferrasol)and a black soil(Acrisol).The treatments included straw addition only(T1);straw addition mineral N(T2);and straw addition tillage(T3).Straw was either buried in the soil or placed on the surface.Sampling was done every 15 days.Placement,addition of external mineral N sources(Urea,46% N),straw type,soil type and exposure duration(15,30,45 and 60 dyas)affected straw decomposition.Decomposition was more in buried straw than in surface-placed straw at all sampling dates in red soil.The addition of an external N source significantly increased decomposition.The study could not,however,fully account for the effect of tillage on straw decomposition because of the limited effect of our tillage method due to the artificial barrier to mechanical iaterference supplicd by the mesh bags.     

氮素对花铃期干旱再复水后棉花纤维比强度形成的影响

2005—2006在南京农业大学卫岗试验站进行盆栽试验,设置正常灌水和棉花花铃期土壤短期干旱处理,每个处理再设置3个氮素水平（N 0、240、480 kg/hm2）,研究氮素对花铃期短期干旱再复水后棉花纤维比强度形成的影响。结果表明,干旱处理结束时,干旱处理棉花的纤维可溶性蛋白含量较正常灌水处理显著降低,而内源保护酶,即:超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性升高,丙二醛（MDA）含量增加;纤维加厚发育相关酶,即:蔗糖合成酶、磷酸蔗糖合成酶、β-1,3-葡聚糖酶和IAA氧化酶的活性均显著降低。在复水后第10d,干旱处理棉花的纤维内源保护酶活性迅速恢复到正常灌水处理水平,MDA含量降低,但纤维发育相关酶的活性仍低于相应正常灌水处理,纤维比强度亦显著低于正常灌水处理。在棉花的纤维加厚发育期土壤短期干旱再复水条件下,以N 240 kg/hm2最有利于形成高强纤维。干旱期间该处理棉花的纤维内源保护酶活性高,细胞膜脂过氧化程度最低,其纤维加厚发育相关酶活性均最高;复水后该处理的纤维内源保护酶活性迅速恢复,MDA含量最低,棉花的纤维加厚发育相关酶活性仍处于最高值,有利于纤维素的合成与累积,最终纤维比强度亦最大。施氮不足（N 0 kg/hm2）或过量施氮（N 480 kg/hm2）均表现出相反的趋势。     

Nonstructural carbohydrates in leaves subtending cotton bolls,fibers and embryos in response to nitrogen stress

A field study was conducted in 2013 and 2014 where cotton was exposed to three N regimes: (1) the control without N application (low N); (2) 260 kg N ha^?1 (medium N); (3) 520 kg N ha^?1 (high N). Boll size, lint mass per boll, seed mass per boll, fiber length and strength were significantly decreased under N deprivation in the two years. The increased carbohydrate levels of LSCB (leaf subtending the cotton boll) led to decreased carbohydrate levels of fibers in the low N relative to the other N treatments. The low N embryos exhibited lower starch concentrations at 17 and 31 DPA (days post anthesis), and TNC (total nonstructural carbohydrate) concentrations at 17, 31, 45 and 52 DPA compared to medium N embryos. Starch levels in LSCB had negative associations with those in fibers at 17, 31 and 45 DPA, but positive associations with those in embryos at 24 and 45 DPA. Fibers expressed negative associations with embryos in glucose level at 24 and 38 DPA, and in TNC levels at 17 and 45 DPA. The study suggests that carbon assimilate levels in fibers and embryos could explain the difference in boll yield components and fiber quality.     

氮素对棉花果枝、果节及蕾铃发生与脱落影响的模拟

为了探明氮素对棉花形态指标与蕾铃脱落的影响,该研究通过设置施氮量试验,以累积温光效应为驱动变量,以花铃期棉株下部果枝对位叶平均氮浓度为氮营养指标,模拟氮营养水平对棉花主要形态指标与蕾铃脱落率的动态影响。结果表明,棉花下部果枝对位叶氮浓度随花后天数呈幂函数下降趋势,其平均氮浓度出现的花后天数占花铃期总天数的比值较稳定,可作为植株N营养状态指标;棉株的果枝数、果节数、成铃数随累积温光效应（cumulative thermal and solar radiative effectiveness,TSE）呈logistic曲线变化,棉蕾数和幼铃数随TSE呈二次曲线变化,且各拟合方程中的参数响应N处理而变化,与花铃期棉株下部果枝对位叶平均氮浓度呈二次函数关系。利用独立的试验资料检验,在不同施氮水平下,棉株果枝数、果节数、棉蕾数、幼铃数、成铃数和脱落率的RMSE分别平均为1.1个/株、2.7个/株、2.4个/株、1.6个/株、1.4个/株和3.5%,模拟值与观测值具有较好的吻合度;在不同种植密度条件下,模拟值与观测值也具有较好的吻合度。本研究可为棉田施肥管理提供参考。     

Response of cotton fiber quality to the carbohydrates in the leaf subtending the cotton boll

This study investigated the effect of nitrogen (N) fertilization on leaf and boll N and carbohydrate concentrations in the development of fiber quality. A two‐year field study was conducted with two cotton (Gossypium hirsutum L.) cultivars, Kemian 1 (average fiber strength 35 cN tex^–1) and NuCOTN 33B (average fiber strength 32 cN tex^–1) at five (2008) and four (2009) N levels. The relationship between leaf and boll N and carbohydrate concentrations was assessed from measurements of N, carbohydrates, chlorophyll (based on SPAD readings), and free amino acids in the leaf subtending the boll, together with fiber carbohydrates and development of fiber quality. Results indicate that leaf N concentration more accurately reflected boll N status than the concentration of chlorophyll or free amino acids. Leaf sucrose and nonstructural carbohydrate had a quadratic relation with leaf N concentration (p < 1%). The optimal leaf N concentration ranged from 3.0% to 2.4%. During 24–38 d post‐anthesis (DPA), fiber sucrose was positively related to leaf sucrose and nonstructural carbohydrate (p < 5%), but was not correlated with leaf starch or total soluble carbohydrates. Fiber strength was positively correlated with fiber sucrose before 38 DPA, and it appeared to be more easily influenced by the fiber sucrose concentration than fiber length, fineness, or maturity. These results suggest that 24–38 DPA is a crucial period for fiber development which might be significantly influenced by physiological and ecological factors. In addition, sucrose or nonstructural carbohydrates in the subtending leaf could be used as a monitoring index to evaluate sucrose levels in the developing fiber, and also for predicting the final fiber strength.     

The difference in the formation of thermotolerance of two cotton cultivars with different heat tolerance

ABSTRACT

In order to study the mechanism of thermotolerance of cotton cultivars with different heat tolerance, the response of yield component and photosynthesis to short-term heat stress (HT; average temperature 34°C) was studied. Pot experiments were carried out in 2015 and 2016 by using cotton cultivar PHY370WR (heat tolerant cultivar) and Sumian15 (heat susceptible cultivar). Results showed that heat (34°C) treatment resulted in a significant (p < 0.05) reduction in cotton yield. Path analysis showed that the direct path coefficient (0.89) of boll weight was higher, compared with the boll number (0.46). With high-temperature stress, it was the difference of boll weight reduction contributed the majority to the difference of yield reduction between cultivars, not the difference of boll number reduction. Different decrease in photosynthesis between cultivars leads to the different decline in boll weight. Different thermotolerance between the two cultivars were as follows: the heat tolerant cultivar could maintain higher photosynthesis rate under HT, and it could recover more quickly and highly in photosynthesis than the heat susceptible cultivar. More importantly, the leaf functional period of heat tolerant cultivar was less shortened by HT than that of heat susceptible cultivar.     

施氮量对棉铃干物质和氮累积及分配的影响

以高品质棉（科棉1号）和常规棉（美棉33B）品种为材料,2005年在江苏徐州（11711E, 3415N）、2007年在河南安阳（11413E, 3604N）设置施氮量（低氮N 0 kg/hm2,适氮N 240 kg/hm2,高氮N 480 kg/hm2）试验,研究施氮量对棉铃干物质、氮累积分配和棉铃（纤维、棉子）品质的影响。结果表明:施氮可改变棉铃各部分干物质和氮素的累积特征,进而影响棉铃重和棉铃品质。在本试验N 240 kg/hm2水平下,单铃棉子和纤维的干物质累积量最大,棉铃各部分（铃壳、纤维、棉子）氮含量适中、氮累积量最高,最终铃重最大,棉纤维和棉子品质最优;在不施氮（N 0 kg/hm2）时,棉铃干物质和氮快速累积期开始较早、累积速率较低,最终干物质和氮累积量均较低,铃重最低,棉纤维和棉子品质最差。在N 480 kg/hm2水平下,棉铃各部分（铃壳、纤维、棉子）的氮含量和累积量提高,且在成熟棉铃中棉纤维干物质的分配系数下降,棉子中的氮分配系数提高,最终棉子中蛋白质含量上升,铃重和棉纤维比强度、棉子油分含量均降低。综上所述,施氮量过低影响棉铃干物质和氮素的累积,而施氮量过高则主要影响棉铃干物质和氮素在铃壳、棉子和纤维间的分配,二者均导致最终的铃重降低、棉纤维和棉子品质变劣。     

氮素营养水平对棉花不同部位叶片衰老的生理效应

通过3个氮素(N)水平(低氮0.kg/hm2、中氮189.50.kg/hm2、高氮395.0.kg/hm2)处理,研究棉花主茎功能叶和不同部位果枝叶衰老过程中的生理生化变化特征。以转基因抗虫棉33B为材料,采用随机区组设计,研究棉花生育期内不同施氮水平下棉花叶面积指数和叶片(主茎功能叶和果枝叶)生理指标(叶绿素含量、可溶性蛋白质含量和丙二醛含量)的差异,分析氮素影响不同部位叶片衰老的效应。结果表明:1)在本试验条件下,盛铃末期为各指标变化的转折点,表明这个时期是叶片生理功能衰老的起始期;2)氮素营养缺乏会引起整体叶片的叶绿素、可溶性蛋白质含量大幅度下降,丙二醛含量升高,加速了叶片的衰老进程;3)当氮素过多时,会加速下部叶片的衰老,上部果枝叶对氮素的缺乏最敏感,因此,施入适量的氮肥,可获得延缓整株叶片衰老的效果。     

Determination of a critical dilution curve for nitrogen concentration in cotton

Several nitrogen (N)‐rate field experiments were carried out in cotton to define dilution curves for critical N concentrations in individual plants (i.e., the minimum N concentration required for maximum growth at any growth stage). Nitrogen application rate had a significant effect on aboveground dry matter, N accumulation, and N concentration. As expected, shoot N concentration in plants decreased during the growing period. These results support the concept of critical N concentration in shoot biomass of single plants as described by Lemaire et al. (2007) and reveal that a dilution curve for critical N concentrations in cotton plants can be described by a power equation. The pattern of critical–N concentration dilution curves was consistent across the two sites. Nitrogen concentration for a given biomass varied greatly with the supply of N. After initial flowering, the N‐nutrition index (NNI) for aboveground biomass of individual plants increased with increasing N rates. Relationships between plant total N uptake and accumulated dry matter in the aboveground biomass can be described by the allometric‐relation equations for each dose of N. Nitrogen‐dilution curves can be used as a tool for diagnosing the status of N in cotton from initial flowering to boll opening. The relationship can also be used in the parameterization and validation of growth models for predicting the N response and/or N requirement of cotton.