除草剂草甘膦对棉田土壤酶活性的影响

为了明确草甘膦对棉田土壤酶活性的影响,于2013年进行室内模拟试验,分别研究了草甘膦不同处理对河南安阳和安徽安庆棉田土壤中过氧化氢酶、脲酶、磷酸酶活性的影响。结果表明,草甘膦按照50~5000mg·kg-1处理对2个采样点土壤中的过氧化氢酶均有抑制作用,并且浓度越高,抑制作用越强;50、250、500mg·kg-1处理对这2个棉田土壤脲酶的影响表现为先抑制后激活,而5000 mg·kg-1处理对安庆棉田土壤脲酶表现为先抑制后激活,对安阳棉田则表现抑制作用;500 mg·kg-1处理对安阳棉田土壤磷酸酶表现为抑制作用,对安庆棉田则表现激活效应,而5000 mg·kg-1处理对这2个棉田磷酸酶均表现出激活效应。统计分析表明,50、250 mg·kg-1处理对这2个棉田土壤过氧化氢酶、脲酶、磷酸酶活性无显著影响,500 mg·kg-1处理对土壤酶活性有显著的影响,但随着培养时间延长逐渐恢复到对照水平,5000 mg·kg-1处理对土壤酶活性的影响达到极显著水平。     

Effects of Exogenous 24-epibrassinolide on Photosynthetic Physiology of CottonSeedlings under Low Temperature

[Objective] The objective of this study was to investigate the effects of exogenous 24-epibrassinolide (EBR) on the photosynthetic physiology of cotton seedlings under low temperature and to provide basis for improving the cold tolerance of cotton by using EBR as growth regulator. [Method] Taking CCRI 60, Lumianyan 28 and Simian 3 as materials, a field experiment was carried out in Institute of Cotton Research of CAAS(Anyang county, Henan province). Before the first low temperature treatment, the cotton seedlings were sprayed with distilled water (Control) and different concentrations of EBR (0.1 mg·L^－1 and 0.2 mg·L^－1), respectively. After 3 days, the relative electrical conductivity, chlorophyll content, rapid chlorophyll fluorescence induction kinetic curve (OJIP) and fluorescence parameters were measured. [Result] Under low temperature, the relative conductivity of CCRI 60, Lumianyan 28 and Simian 3 spraying with EBR decreased by 17.7%～32.8% compared with control, and there was no significant difference between CCRI 60 and Lumianyan 28 in different concentrations of EBR treatments, butthe relative conductivity of Simian 3 treating with 0.2 mg·L^－1 EBR was significantly lower than those treatments with 0.1 mg·L^－1 EBR . The chl a and chl b contents increased by 9.7%～32.6% and 15.0%～18.9%, respectively. The maximum photochemical efficiency of photosystemⅡ (F_v/F_M) and photosynthetic performance index on absorption basis(PI_ABS) increased significantly. PI_ABS of CCRI 60 increase the maximum by 75.6% using 0.1 mg·L^－1 EBR. Lumianyan 28 and Simian 3 increased the maximum by 101.1% and 265.6% using 0.2 mg·L^－1 EBR, respectively; Absorbed photon flux per cross section (ABS/CSm), electron transport flux (further than QA) per active reactive center (ETo/RC) and probability for electron transport (φEo) are significantly increased. [Conclusion] Exogenous EBR can enhance the ability of low temperature tolerance of cotton seedlings and alleviate the inhibition of photosynthesis in cotton at low temperature. The study showed that 0.1 mg·L^－1 EBR performs well in CCRI 60 and 0.2 mg·L^－1 in Lumianyan 28 and Simian 3.     

铜基营养保护剂对棉花生长和产量的影响

2013―2014年采用盆栽试验研究了不同种类及浓度的铜基营养保护剂对棉花生长、产量及防病效果等的影响。结果表明:4种铜基营养保护剂在喷施质量浓度为1 g·L-1和2 g·L-1时,与喷施清水相比,皮棉产量分别增加4.22%~13.38%和21.89%~38.36%;增加了棉株地上部干物质质量,最高达23.96%;降低了棉花病情指数26.75%~40.91%和22.78%~37.78%,但处理间差异不显著。因此,在棉花上喷施铜基营养保护剂既可促进棉花生长,增加棉花产量,又可提高棉花的防病效果。     

Effects of Melatonin on the Antioxidant Enzyme Activities and Seed Germination of Cotton (Gossypium hirsutum L.) under Salt-Stress Conditions

[Objective] Cotton (Gossypium hirsutum L.) seed germination, in which melatonin plays an important regulatory role, is seriously affected by soil salinization. Cotton seed germination, antioxidant enzyme activity levels and other physiological indicators were analyzed to clarify the regulatory effects of exogenous melatonin on cotton seed germination under salt-stress conditions. [Method] The experiment was conducted in a greenhouse of Hebei Agricultural University in Baoding City, Hebei Province from 2018 to 2019 using Guoxin Cotton 9 as the material. The germination rate, germination potential, seed biomass after germination, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities, as well as the malondialdehyde (MDA) content, of cotton seeds were measured after exposure to different melatonin concentrations (0, 10, 20, 50 and 100 μmol·L^－1) and 150 mmol·L^－1 NaCl treatments. [Result] After germination, the germination rate, germination potential, radical length and seed biomass significantly decreased, as did the SOD, POD and CAT activities. However, the MDA content significantly increased under salt-stress conditions. Low exogenous melatonin concentrations (10 and 20 μmol·L^－1) increased the germination potential, germination rate and biomass of cotton seeds, and promoted the elongation of radicals; however high melatonin concentrations (50 and 100 μmol·L^－1) inhibited cotton seed germination and decreased seed biomass after germination. Low melatonin concentrations (10 and 20 μmol·L^－1) increased the SOD, POD and CAT activities and decreased the MDA content in cotton seeds. [Conclusion] Low melatonin concentrations could promote germination and improve the salt tolerance of cotton seeds, while high melatonin concentrations could inhibit their germination. A 20 μmol·L^－1 melatonin concentration is appropriate for regulating cotton seed germination under salt-stress conditions.     

Generation and Glyphosate Resistance Analysis of G10eve Transgenic Cotton

[Objective] Novel germplasm of cotton was generated for development of cultivars with high resistance to glyphosate. [Method] The glyphosate resistance gene G10eve was preliminarily analyzed using bioinformatics methods and introduced into 'Coker 312' via Agrobacterium-mediated transformation. The expression of G10eve was estimated by PCR (Polymerase chain reaction) and qRT-PCR (Quantitative real-time PCR). The content of shikimic acid and tolerance to glyphosate were determined in response to application of glyphosate to 'Coker 312' and transgenic plants. [Result] A total of 28 independent positive transgenic lines were obtained. The transformation efficiency and the rate of seedling differentiation were up to 49.3% and 40.6%, respectively. PCR and qRT-PCR analysis showed that G10eve was integrated into the cotton genome, and the G10eve expression level differed significantly among the transgenic lines. At the cotyledon stage, the transgenic cotton showed resistance to 8 mL·L^－1 glyphosate, whereas 'Coker 312' showed phytotoxicity to the 2 mL·L^－1 glyphosate treatment. No significant accumulation of shikimic acid was detected in transgenic plants before or after glyphosate treatment, which indicated the typical physical characteristic of glyphosate resistance. [Conclusion] Overexpression of G10eve in cotton improved resistance to glyphosate. Thus, novel germplasm of cotton resistant to glyphosate was generated.     

棕色棉茎尖基因枪遗传转化

为了建立高效的棉花茎尖遗传转化体系,以棕色棉品种新彩棉5号为材料,采用茎尖培养和基因枪遗传转化方法,通过对凝固剂种类、活性炭含量、卡那霉素浓度、渗透处理时间、轰击压力、轰击距离等因素的优化,建立了棕色棉新彩棉5号茎尖基因枪遗传转化技术体系。结果表明,不同凝固剂种类、活性炭含量、卡那霉素浓度、渗透处理时间、轰击压力和轰击距离对棕色棉茎尖转化率有明显影响。最佳的遗传转化体系为:前渗处理4 h,轰击压力7.586 MPa(1100 psi),轰击距离9 cm,轰击后恢复培养4 d,然后在MSB+8 g·L~(-1)琼脂+125mg·L~(-1)卡那霉素筛选培养基中筛选25 d。获得抗性芽后,在添加1 g·L~(-1)活性炭的生根培养基中诱导抗性芽生根,并获得抗性再生植株。通过PCR和q PCR检测,5200个茎尖共获得16株阳性转基因植株,转化率为0.31%。该技术体系的建立为棕色棉的遗传转化奠定了基础,为彩色棉育种提供了新的材料。     

Interaction of Plant Density with Mepiquat Chloride Affects Plant Architecture and Yield in Cotton

[Objective] The effect of planting density and mepiquat chloride (DPC) on cotton plant architecture, growth, yield, and quality at Anyang City, Henan Province, China, was studied. [Method] Field experiments with cotton variety Lumianyan 28 were conducted with five planting densities (15 000, 45 000, 75 000, 105 000, and 135 000 plants·hm^－2) and application of DPC at three concentrations (0, 195, and 390 g·hm^－2). [Result] Increasing cotton plant density resulted in increased internode length and plant height but also caused the decrease of inclination of fruiting branches and leaves as well as elevated dry matter allocation to leaves and fruiting branches, which led to a decrease in dry matter accumulation. Application of DPC reduced the azimuth angle of fruiting branches and plant height, but increased the insertion angle of fruiting branches with the main stem, leaf length, and petiole length. Planting density and DPC treatment showed a significant interaction on fruiting branch insertion angle, plant height, stem diameter, and dry matter allocation to fruits and leaves. The interaction of DPC and planting density had a complementary effect on the spatial distribution of cotton-yielding bolls. The final dry matter was highest (14 362 kg·hm^－2) at the planting density of 105 000 plant·hm^－2 and DPC application of 390 g·hm^－2, which resulted in the highest seed yield (3 257 kg·hm^－2). [Conclusion] For maximization of cotton yield and quality, a plant density of 75 000 to 105 000 plants·hm^－2 and DPC application of 195 to 390 g·hm^－2 in the Yellow River cotton-producing region is recommended. The results may help to optimize labor-saving cotton management and to generate a plant architecture suitable for mechanical harvesting in the Yellow River cotton-producing region.     

不同咸水利用方式对棉花叶绿素荧光参数及土壤盐分的影响

【目的】本研究旨在科学合理地利用浅层咸水资源。【方法】依托短期定位试验开展了在第3年和第4年不同咸水利用方式下(CK:造墒和蕾期灌淡水;T1:造墒和蕾期灌咸淡混配矿化度3 g·L^-1的微咸水;T2:淡水造墒蕾期灌矿化度5 g·L^-1咸水;T3:造墒和蕾期灌矿化度5 g·L^-1咸水;T4:淡水造墒蕾期不灌水)棉花长势、叶绿素荧光参数、土壤盐分累积及其运移的变化。【结果】T1和T2处理的齐苗率、株高、干物质质量、叶面积指数、叶绿素荧光参数、产量及霜前花率与CK无显著差异,土壤盐分含量较CK有所增加,但未对棉花生长产生明显抑制。T3处理的棉花长势指标、叶绿素荧光参数较CK显著降低,0~100 cm土壤盐分含量较CK明显增加。【结论】从土壤质量安全和咸水高效利用的角度考虑,连续4年用3 g·L^-1的咸淡混合水灌溉或用淡水与5 g·L^-1的咸水轮灌不仅能节约淡水,且不影响棉花产量。本研究结果为当地在棉花生产中安全利用咸水提供技术参考。     

秸秆还田对滨海盐碱地棉苗光合特性及生长的影响

为探讨秸秆还田对滨海重度盐碱地棉苗光合特性及生长的影响,设置增施有机肥、播前秸秆还田、冬前秸秆还田3个处理,测定了棉花苗期3个层次土壤含盐量、水分和容重,棉花叶片光合参数、叶片SPAD值以及干物质积累和棉花产量。结果表明,与对照相比,增施有机肥和秸秆还田的处理各个土层含盐量和容重明显降低,棉苗叶片LAI和SPAD明显增大,光合能力提高,干物质积累量、根冠比以及棉花产量明显增加。其中,冬前秸秆还田各土层含盐量低于2.00 g·kg-1,容重保持在1.15~1.40 g·cm-3,叶片SPAD值高于40.0,LAI提高65.5%,光合性能系数增高23.4%~92.8%,非光化学淬灭系数(NPQ)降低12.2%,干物质积累总量增大46.3%,根冠比提高56.5%,产量提高36.2%。因此,在本试验条件下,冬前秸秆还田更有利于滨海盐碱地改良及棉苗的正常生长。     

Applying Plant Growth Regulators at Early Stages Affects Maturation of Cotton

[Objective] Early initiation and early maturity are the foundation of high yield and good quality of cotton. The purpose of this study is to determine the effects of plant growth regulators applied at the seedling and squaring stage on the early initiation of flower bud and the rate of the opened cotton boll (ROCB) during later development period, and to provide practical measures for hastening the maturity of cotton. [Method] Several plant growth regulators were applied from cotyledonary to squaring stage under greenhouse and field conditions, water was used as the control. The first fruiting branch node (indicating the initiation of flower bud), the number of bud prior to blooming and the ROCB at mid-term of boll maturation period (23 September, 2017) were compared among treatments. [Result] Under greenhouse conditions, gibberellic acid (GA₃) applied at the cotyledonary stage with 140 μmol·L^－1 as well as the three consecutive applications of sodium nitrophenolate (CSN, 2.23 μmol·L^－1) at the cotyledonary, two-leaf and four-leaf stage made the first fruiting branch node move down by about 0.9 nodes. In field experiments, the application of gibberellin₄₊₇(GA₄₊₇, 288 and 576 μmol·L^－1) at the cotyledonary stage significantly decreased the first fruiting branch node by about 0.4 nodes. Also, the application of 6-benzylaminopurine (6-BA, 44.4 μmol·L^－1) at the three-leaf stage significantly decreased the first fruiting branch node by 0.2 nodes. However, there was no significant correlation between the first fruiting branch node and the ROCB in late September. Moreover, the application of Brassinolide (BR, 0.10 μmol·L^－1) at the bud stage increased the ROCB in late September, which was mainly associated with the increased boll set in the lower and middle fruiting branches. [Conclusion] The reasonable distribution of bolls (concentrated in the lower and middle fruiting branches as well as inner fruiting sites) is more important for the earliness of cotton than lowering the first fruiting branch node.     

脱落酸对棉花体细胞胚胎发生的影响

【目的】研究脱落酸(Abscisic acid, ABA)对棉花体细胞胚胎发生过程中下胚轴脱分化和再分化的影响,优化体细胞胚胎发生体系和初步解析脱落酸调控棉花体细胞胚胎发生分子机制。【方法】以棉花品种中棉所24(CCRI 24)下胚轴为外植体,设置5个ABA浓度0、0.02、0.04、0.06、0.08μmol·L^-1,分别以A0、A1、A2、A3、A4表示,添加至MSB(MS培养基+B5维生素)培养基诱导愈伤和胚性愈伤,研究ABA对棉花下胚轴初始细胞脱分化、愈伤组织诱导和胚性愈伤组织诱导的影响。【结果】ABA促进下胚轴初始细胞脱分化;显著提高愈伤组织的脱分化率和增殖率;0.02μmol·L^-1ABA显著提高胚性愈伤分化率,0.04~0.08μmol·L^-1ABA显著降低胚性愈伤分化率。ABA处理后胚性愈伤和非胚性愈伤的增殖率均显著提高且质地受到影响。0.02~0.08μmol ABA处理下,LBD和LBD在愈伤起始期上调表达。0.02μmol·L^-1ABA处理下,在愈伤增殖早期和中期BBM、LEC1和AGL15上调表达,愈伤增殖后期FUS3、LEA、ABI3基因上调表达。【结论】脱落酸调控的棉花体细胞胚胎发生与相关标记基因的时空性表达密切相关,这些基因表达水平的增加是ABA调控愈伤和胚性愈伤分化的分子基础。     

中国北方主要棉区土壤供钾能力及其与产量和品质的关系

2012―2013年在山东平原县、河北威县、新疆昌吉市代表性棉田上采集土壤(0~20 cm)和棉花样品,分析北方棉区土壤钾素状况、供钾能力及其与棉花产量和纤维品质的关系。结果表明,平原、威县、昌吉棉田速效钾含量平均分别为217、128、232 mg·kg-1,供钾能力平均分别为128.2、105.1、213.6 kg·hm-2,每生产100 kg皮棉棉花地上部分别吸收K 9.77、7.82、12.25 kg。不同棉区土壤速效钾含量与皮棉产量和地上部吸钾量相关性不同,在平原和昌吉,当土壤速效钾含量分别小于123 mg·kg-1和220 mg·kg-1时,与皮棉产量和地上部吸钾量具有显著正相关。3个植棉区棉花的吸钾量与子棉产量、皮棉产量都呈显著的正相关。棉花地上部吸钾量、纤维吸钾量和纤维含钾量与纤维品质指标的相关性不同地点差异大。     

A Regeneration System for Cotton Variety Xinluzao 45 via Somatic Embryogenesis

[Objective] The purpose of this study was to expand upland cotton genotypes suitable for regeneration via somatic embryogenesis, so as to provide excellent receptor materials for the genetic transformation of cotton. [Method] Six different hormone combinations were studied to establish a somatic embryo regeneration system for hypocotyl explants of Xinluzao 45, a widely planted variety in Xinjiang Province. [Result] Faint yellow callus was induced on a medium consisting of hormone combinations C1 (0.1 mg·L^－1 acetic acid dichlorobenzene oxide [2, 4-D] + 0.1 mg·L^－1 kinetin [KT]) or C5 (0.1 mg·L^－1 2, 4-D + 0.5 mg·L^－1 indo-3-butyric acid + 0.1 mg·L^－1 KT). The generated callus was able to successfully induce embryogenic callus on hormone-free medium containing doubled KNO3. The embryogenic callus then developed into somatic embryos and regenerated plants. Maximum rates of callus induction and regeneration were 92.2% and 40.3%, respectively. Although no significant difference was observed in the rate of callus induction of Xinluzao 45 hypocotyls between hormone combinations C1 and C5, the incidence of induced embryonic callus was higher on C1 than on C5. [Conclusion] The somatic embryo regeneration system developed in this study provides technical support that will facilitate Agrobacterium-mediated transformation of upland cotton Xinluzao 45.     

Nitrogen Fertilizer and Its Residual Effect on Cotton Yield and Biomass Accumulation

[Objective] The optimum nitrogen rate of 300 kg·hm^－2 is well documented for cotton in the Yangtze River Valley, China. It can be reduced to 225 kg·hm^－2 without reducing yield in late sowing under high planting density. The aim of this study was to determine the possibility of further reducing the nitrogen application rate at the first flower stage, its residual effects and influence on cotton yield formation rule. [Method] A pot experiment was conducted with five nitrogen levels (120, 150, 180, 210 and 240 kg·hm^－2) in 2014, but only 180 kg·hm^－2(for studying nitrogen residual effect) in 2015, to study the cotton growth process, yield and its components and biomass accumulation. [Result] Nitrogen levels significantly affected the yield and biomass accumulation, but not the growth process and nitrogen residual effect. Maximum seed cotton yield (30.5 g·plant^－1), boll weight (3.8 g) and biomass accumulation, especially in the reproductive and vegetative organs, was recorded in the 180 kg·hm^－2 nitrogen treatment. In the rapid accumulation period, the proportion of biomass accumulation in the reproductive organs was the highest. [Conclusion] In a soil with medium fertility level, the application of 180 kg·hm^－2 nitrogen was optimal, because the strength of biomass accumulation in reproductive organs increased during the rapid accumulation period.     

Determination of Phytic Acid in Cottonseed Kernels by Ion Chromatography

Cottonseed meal is an important plant protein resource of feed industry and breeding industry, although it contains many antinutritional factors. Phytic acid, as one of the mainly antinutritional factor, cannot be digested easily by monogastric animals, such as fowls and pigs, consequently results in the decreased bio-availability of material elements and leads to the environment pollution by the phytate in excreta. Thus far, study of breeding cottons containing low phytic acid gradually becomes the hotspot, and the method of fully extracting phytic acid from cotton seeds and precise measurement is becoming more and more important and necessary. A new method for the rapid extraction and determination of phytic acid in cottonseed kernels by ion chromatography was developed in this study. After the diethyl ether treatment of dry cottonseed kernel powder, the samples were suspended in 10ml 0.66 mol·L^－1 HCl and boiled for 1 hour. Then the samples were shaken at 4 ℃ for 12 hours and centrifuged. The supernatant was diluted and purified for loading. To analyze the sample, DIONEX ICS-2000 ion chromatography, AG11-HC Guard (4 mm×50 mm) protection column and AG11-HC Guard (4 mm×250 mm) separation column were used in controlled conditions (washing buffer: 30.0 mmol·L^－1 KOH; ream speed: 1.0 mL·min^－1; collecting time: 25 min; 75 mA current; temperature: 30 ℃; loading amount: 20 μL). The results showed that R2 of linear regression is 0.999, which means the regression relation is great. In addition, the standard deviations of all the indexes are within 5% and the average recovery rate is 98.64%-102.31%. The detection limit, showing the minimum detectable concentration of analyte in the sample, is 0.059 μg·mL^－1, and the quantitation limit, showing the minimum amount of analyte in a sample can be quantitatively determined, is 0.196 μg·mL^－1. This method is easy and accurate with great reproducibility, showing a strong application value.     

利用光谱-盐分指数监测棉田土壤盐分

通过对棉田土壤盐分的光谱反演研究,为土壤盐渍化遥感动态监测提供可能。利用ASD地物光谱仪测定新疆兵团第六师共青团农场盐渍化棉田土壤光谱,结合土壤化学参数分析确定反映棉田土壤盐渍化程度的敏感波段,构建最佳盐分指数对棉田土壤盐分进行监测。结果表明,随盐渍化程度(0.084~1.659 g·kg-1)的加重,土壤光谱反射率呈上升趋势,在近红外区(1350~1850 nm)差异尤为显著,该波段范围光谱反射率与土壤盐分呈极显著相关(r=0.880**),且对土壤盐分响应敏感,为识别盐渍化土壤的敏感波段;选择盐渍化光谱敏感波段建立了盐分指数SI1,BI,SI2,NDSI,SI3监测棉田土壤盐渍化的模型,其中SI1和BI的RMSE分别为0.151和0.149、RE为7.5%和6.3%,预测能力强,可推荐为棉田土壤盐分监测的最佳模型。     

种植密度和缩节胺调控对麦后直播棉产量和冠层特征的影响

2013―2014年以早熟棉(中棉所50)为材料,采用裂区设计,在江苏省南京市研究了种植密度(7.50万、9.75万和12.00万株·hm~(-2))和缩节胺(DPC)调控(0,52.5和105.0 g·hm~(-2))对麦后直播棉产量和冠层特征的影响。结果表明:皮棉产量在不同种植密度下以12.00万株·hm~(-2)处理最低,在不同DPC用量水平下以0 g·hm~(-2)处理最低;种植密度与DPC调控存在互作效应,以种植密度9.75万株·hm~(-2)、DPC用量52.5~105 g·hm~(-2)处理产量较高,且产量构成中以铃数对产量的直接效应最大。对冠层特征影响表明,下部果枝夹角和长度随种植密度增加而降低,而中、上部果枝的夹角和长度、叶面积指数均以种植密度9.75万株·hm~(-2)处理较高;不同部位果枝夹角和长度、叶面积指数均随DPC用量增加而降低,而透光率则相反。相关分析表明,下部果枝夹角大、中部果枝较长及上部果枝夹角小且叶面积指数和透光率较高,有利于提高产量和霜前花率。综上,该棉区麦后直播棉种植密度9.75万株·hm~(-2)、DPC用量52.5~105 g·hm~(-2)(蕾期、开花期和打顶后用量比例为1∶2∶4),有利于改善棉花冠层特征,实现早熟高产。     

Effects of Low Phosphorus Stress on Root Morphology and Physiological Characteristics of Different Cotton Genotypes at the Seedling Stage

[Objective] Phosphorus is one of three major required nutrients for cotton growth and development. A phosphorus deficiency will lead to retarded cotton growth, undeveloped roots, and the abscission of buds and bolls, which results in serious reductions in cotton yield and quality. While applied phosphorus is easily fixed in soils, it is mostly transferred to occluded P, which is not available to plants. Therefore, this study aimed to provide theoretical support for the study of response mechanisms to low phosphorus stress and the efficient phosphorus uptake and utilization of different cotton genotypes. [Method] The effects of phosphorus accumulation and utilization, leaf photosynthetic characteristics and root morphology of two genotypes of cotton (CCRI 79 and SCRC 28) were studied in hydroponic cultures having different phosphorus concentrations. [Result] CCRI 79 had higher phosphorus utilization rates of 90.92 mg·mg^－1 at the low phosphorus level (KH2PO4 1.0×10^－5 mol·L^－1) and 23.09 mg·mg^－1 at the high phosphorus level (KH2PO4 0.5 mol·L－1) compared with SCRC 28. When phosphorus was deficient, the total root length, total root surface area and total root volume of SCRC 28 increased by 13.05%, 18.78% and 10.50%, respectively, while the total root length, total root surface area and total root volume of CCRI 79 decreased significantly. [Conclusion] Here, we found that SCRC 28 had a root morphology and physiological characteristics that allowed it to adapt to low phosphorusstress, while CCRI 79 utilized phosphorus more efficiently.     

Effects of the Seed Film Coating Salicylic Acid on the Chilling Tolerance of Cotton Seedlings

The objective of this study was to investigate the effect of the different concentrations of the seed film coating salicylic acid on the cold tolerance of cotton seedlings using the sand culture method. The physiological response of cell membrane permeability, protective enzyme activity and osmotic adjustment of cotton seedling were measured before and after at low temperature stress and at normal temperature. The results showed that 1-10 mmol·L^－1 of seed film coating with salicylic acid seed coating treatment could effectively alleviate damage to cotton seedlings at low temperature, and the accumulation of the relative electrical conductivity and malondialdehyde were reduced on cotton seedlings. The activity of superoxide dismutase, peroxidase, catalase, and soluble protein, soluble sugar and proline contents increased sharply. These results indicate that film coating with salicylic acid can alleviate the effects of low temperature stress on seedling growth inhibition and improve the cotton seedlings by providing chilling tolerance, and the optimum treatment concentration salicylic acid is 5 mmol·L^－1.     

Effects of Exogenous Proline on the Growth,Physiological Characteristics,and Proline Metabolism of Cotton Seedlings under Boron Deficiency Stress

[Objective] This study investigates the effects of exogenous proline on the growth, physiological responses, and proline metabolism of cotton (Ekang No.8) seedlings treated with varying boron (B) concentrations. [Method] We conducted a randomized experiment with six treatments using the hydroponic method in a greenhouse at Huazhong Agricultural University. We applied three different concentrations of boron, including 0.02 μmol·L^－1 (low-concentration B), 2.5 μmol·L^－1 (medium-concentration B), and 100 μmol·L^－1 (sufficient-concentration B). The first two are boron-deficient treatments. We also applied an exogenous proline treatment at 20 μmol·L^－1(0 μmol·L^－1 as control). When any significant difference among the treatments were observed, the related indicator was measured. [Result] The results showed that exogenous proline inhibited the growth of cotton seedlings under sufficient-concentration B treatment while promoting the absorption of B by roots under low-concentration B treatment. The application of exogenous proline to the seedlings under low-concentration B treatment reduced the contents of proline and H₂O₂ in leaves but increased the accumulation of MDA and H₂O₂ in roots. The activities of SOD and antioxidant enzymes (APX) in the roots and leaves were dramatically enhanced. Conversely, POD activity reduced significantly and there was no significant change in CAT activity relative to low-concentration B treatment. More importantly, we found that the application of exogenous proline under B deficiency increased the activities of P5CS, P5CR, OAT (synthetase), and PRODH (degrading enzyme) in proline metabolic pathways. [Conclusion] Applying exogenous proline under sufficient-B concentration inhibits growth. The application of proline to seedlings under low-B concentration promotes the absorption of B by roots, increases the activity of APX, and decreases the membrane lipid peroxidation in leaves. A B deficiency leads to proline accumulation in plants. The addition of proline under low-B concentration can reduce the proline content in leaves, which is caused by affecting the critical synthetase and catabolic enzyme activities in the proline metabolism pathway (Glu and Orn pathway). The main reason for this occurrence is the significant increase of proline dehydrogenase (PRODH) activity.