For the purpose of dissecting the mechanism of root growth in response to potassium (K) deficiency in cotton (Gossypium hirsutum L.), young seedlings of NuCOTN99B grown in half-strength modified Hoagland’s solution with low K nutrient (0.05mmol L-1) were investigated for the root configuration, content of endogenous free indole acetic acid (IAA), and amount of ethylene released from the roots 4 d after treatment. Compared with the treatment with moderate K nutrient (0.50mmol L-1, control), the K deficient treatment significantly inhibited root length and the formation of lateral roots. The reduced lateral roots mainly resulted from the shortened branched root zone, and there was no change in the lateral root density. Under K deficient condition, the greatest reductions for root length, total root surface area, and root volume occurred in fine roots (0.05mm diameter<0.20mm), followed by the coarse roots (diameter 0.45mm) and the middle roots (0.25mm diameter<0.45mm). The fine roots were more important in nutrient uptake than the middle and the coarse roots. Thus, the K starving damage was greater in cotton seedlings than the growth inhibition of roots. When the cotton seedlings exposed to K deficient media for 4 d and 10 d, the total root length and the total root surface area were 35.7-38.0% and 47.7–50.6% of the values of the control plants; whereas the K accumulation was approximately 25% and 16% to the control values, respectively. As expected, the endogenous free IAA content in the roots grown in K deficient media reduced by 50%, whereas the amount of ethylene released from roots increased by nearly 6-fold, which partially explained the inhibition of lateral root formation and root elongation by K deficiency.

The objective of the present study was to elucidate the mechanism of tolerance to potassium (K) deficiency in cotton (Gossypium hirsutum L.) through comparing the differences of K uptake, translocation, and utilization in a K-efficient cultivar Liaomian 18 (non-Bt cotton) and a K-inefficient cultivar NuCOTN99B (American Bt cotton). The seedlings of the 2 cultivars were hydroponically cultured in a growth chamber and treated with sufficient K of 2.5 mmol L

Coronatine is a phytotoxin that affects the accumulation of defence-related metabolites in plants but information on how its effects may be mediated by environmental stress is scanty. An experiment was carried out to determine the changes in growth, gas exchange, relative water content, chlorophyll (Chl) content, antioxidant enzymes and lipid peroxidation in maize (Zea mays L., var. Nongda 3138’) seedlings treated with coronatine under simulated drought stress. Seedlings raised hydroponically in a growth chamber with simulated drought for 8d (longperiod drought) or 3d (short-period drought) were treated with or without coronatine at the three-leaf stage. Under the drought condition, treated with coronatine signifi cantly increased the fresh weight and relative water content in leaves of seedling leaves. The increase was accompanied by increased rates of photosynthesis and transpiration, and the maintenance of Chl pigments. Coronatine had no effects on catalase (CAT), guaiacol peroxidase (POD) and glutathione reductase (GR) under normal condition, but it signifi cantly enhanced activities of CAT, POD and GR in stressed seedlings under the long-period drought treatment. Under the short-period drought treatment, the POD and GR activity in the seedlings treated with coronatine were much higher than in those not treated. Malondialdehyde (MDA) increased sharply under drought condition, but treatment with coronatine signifi cantly reduced it by 15%. The total Chl content of leaves under the drought condition was markedly increased by the treatment with coronatine. Seedlings subjected to a short-period drought had reduced water content, but recovered fairly well by the treatment with coronatine with negligible effects on most physiological and biochemical processes. The application of coronatine alleviated the drought stress in maize seedlings and enhanced their tolerance of water stress through changes in physiological and anti-oxidant enzyme activities.

Coronatine (COR) is a chlorosis-inducing phytotoxin that mimics some biological activities of methyl jasmonate. This study investigated whether COR confers salinity tolerance to cotton and whether such tolerance is correlated with changes in the activity of antioxidant enzymes. COR at 0.01 mM was applied hydroponically to cotton seedlings at the two-leaf stage for 24h. A salinity stress of 150mM NaCl was imposed after completion of COR treatment for 15 d. Salinity stress reduced biomass of seedlings and increased leaf superoxide radicals, hydrogen peroxide, lipid peroxidation, and electrolyte leakage. Activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and glutathione reductase (GR), and of the stable free radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH), scavenging activity were altered by salinity to varying degrees. Pretreatment with COR increased the activities of CAT, POD, GR, and DPPH scavenging activity in leaf tissues of salinity-stressed seedlings. Thus, COR might reduce the production of reactive oxygen species by activating antioxidant enzymes and DPPH-radical scavenging, thereby preventing membrane peroxidation and denaturation of biomolecules.

This study investigated whether uniconazole confers drought tolerance to soybean and if such tolerance is correlated with changes in photosynthesis, hormones and antioxidant system of leaves. Soybean plants were foliar treated with uniconazole at 50 mg L 1 at the beginning of bloom and then exposed to water deficit stress at pod initiation for 7 d. Uniconazole promoted biomass accumulation and seed yield under both water conditions. Plants treated with uniconazole showed higher leaf water potential only in water-stressed condition. Water stress decreased the chlorophyll content and photosynthetic rate, but those of uniconazole-treated plants were higher than the stressed control. Uniconazole increased the maximum quantum yield of photosystemand ribulose-1,5-bisphosphate carboxylase/oxygenase activity of water-stressed plants. Water stress decreased partitioning of assimilated 14C from labeled leaf to the other parts of the plant. In contrast, uniconazole enhanced translocation of assimilated 14C from labeled leaves to the other parts, except stems, regardless of water treatment. Uniconazole-treated plants contained less GA3, GA4 and ABA under well-watered condition than untreated plants, while the IAA and zeatin levels were increased substantially under both water conditions, and ABA concentration was also increased under water stressed condition. Under waterstressed conditions, uniconazole increased the content of proline and soluble sugars, and the activities of superoxide dismutase and peroxidase in soybean leaves but not the malondialdehyde content or electrical conductivity. These results suggest that uniconazole-induced tolerance to water deficit stress in soybean was related to the changes of photosynthesis, hormones and antioxidant system of leaves.

Seedling responses of two transgenic Bacillus thuringiensis (Bt) cotton (Gossypium hirsutum L.) cultivars, 99B and SGK9708-41, to salinity stress were studied under 0, 50, 100 and 200mM NaCl treatments. Cotton seedling growth, indicated by height, leaf area, and fresh and dry weights, of both cultivars was reduced by NaCl in a concentration-dependent manner. Total N concentrations of seedling roots, stems and leaves of both cotton cultivars decreased with increasing NaCl concentrations. For both cultivars, soluble protein content increased in leaves and decreased in stems due to salt stress, and decreased in roots by 50 and 100mM NaCl. Bt protein concentrations in leaves of both cultivars were decreased by salt stress, but still were biologically effective to control the neonate bollworm larvae in seedling cotton.

研究了影响棉花钾吸收动力学参数的因素，初步确定了钾吸收动力学方法在棉花上应用的条件，比较了转基因抗虫棉新棉99B和常规棉中棉所35苗期的钾吸收特性。结果表明，棉花钾吸收动力学参数受到苗龄、耗竭液中起始钾浓度及培养液中钾浓度的显著影响，在苗龄较小（3～4叶苗与4～5叶苗相比）、耗竭液中起始钾浓度较高（0.35与0.2mmol•L-1相比）、培养液中钾浓度较高（2.0与0.5mmol•L-1相比）的情况下，Km、Cmin均比较高，而Imax在前两种条件下较高、在后一种条件下较低。在5～6叶期，新棉99B的Imax显著降低于中棉所35，而Km、Cmin显著高于后者（培养液中K+为0.5mmol•L-1），耗竭液中起始K+为0.2mmol•L-1），说明新棉99B吸收有限钾的能力低于中棉所35。

应用ICP-MS系统检测了甲哌锚处理对转Bt基因抗虫棉棉籽中各种无机元素含量的影响，结果表明：ICP-MS可以迅速、有效地检测出棉籽中54种无机元素的含量。其中K，P，Mg，Ca，Na五种人体必需宏量元素，含量范围为138.3～13 835.1μg•g-1；14种人体必需微量元素含量范围为14.2ng•g-1～81.7μg•g-1，从高到低依次为Si，B，Mn，Sr，Zn，Ni，Cu，Mo，Fe，Co，Se，V，I，Sn；五种重金属元素含量范围为0.1～455.3ng•g-1，从高到低依次为Pb，Cd，Cr，As，Hg；甲哌鎓处理显著降低了人体必需宏量元素Ca、微量元素Fe，Si，Mn，Co，Ni，Cu，I含量；重金属Pb，Cd和Cr含量分别降低68%，67%和54%，均达显著水平，对其他宏量、微量元素无显著影响。对于棉籽中的其他30种元素，甲哌鎓处理显著提高了La等八种元素、降低了W等七种元素含量。这些结果表明，甲哌鎓处理一定程度上增加了棉籽作为食油用的安全性。

为了满足棉花叶片衰老（以缺钾诱导）过程中根冠通讯研究的需要，在营养液培养条件下探索了棉花子叶期至一叶期幼苗的单接穗单砧木嫁接、双接穗单砧木（Y型）和单接穗双砧木（A型）嫁接技术。通过研究营养液中钾浓度、砧木和接穗的苗龄配合、嫁接部位及砧木保留子叶对嫁接成活率的影响，综合考虑嫁接成活率和成活后用缺钾诱导嫁接苗衰老的速度，确定单接穗单砧木嫁接和Y型嫁接的砧木均在不含钾的沙床中出苗后（萌发后3d）转移至钾浓度为0.1 mmol L-1（中度钾胁迫）的1/2改良Hoagland营养液中培养5d至第1片真叶出现，接穗在不含钾的沙床中出苗后（萌发后3d）再生长2d，采用砧木留子叶法在子叶节处嫁接。A型嫁接的适宜条件和方法为砧木和接穗苗龄（第1片真叶刚出现）相同，嫁接前的培养方法同Y型砧木，嫁接部位在砧木子叶节下2-3cm处。单接穗单砧木、Y型和A型嫁接的平均成活率分别可达到95%、85%和90%以上。

缺钾及冈缺钾而导致的早衰已成为当前我国棉花生产的主要限制囚素，而根系的生长发育与钾素营养互相影响、关系密切。本试验在生长室内营养液培养条件下，调查缺钾对棉花幼苗根系性状的影响，测定根系游离吲哚乙酸（IAA）和乙烯释放量。结果显示，与适钾处理（0.50mmol L-1）相比，缺钾处理（0.05 mmol L-1）显著抑制了根系伸长和侧根发生，而且侧根的减少主要由侧根发生区的缩短所致，侧根发生密度并无变化，似乎缺钾减慢了侧根发育的进程。但不改变可以形成侧根的中柱鞘细胞的发育状况。此外，细根（0.05-0.20mm）生长受缺钾的影响最大，绝对根长、根表面积、根体积及其占总根系的比例均显著降低；中等根（0.25-0.45mm）受到影响最小，粗根（>0.45mm）居中。由于细根的吸收活性强于中等根和粗根，因而缺钾幼苗的钾营养状况较根系牛长更为恶化，处理4d和10d的整株钾积累最仅分别为适钾处理的25%左右和16%左右，而其总根长和根系总表面积分别相当于适钾处理的35.7%-38.0%（处理4d）和47.7%～50.65（处理10d）。与适钾条件相比，缺钾使根系的游离吲哚乙酸（IAA）含量降低约505，而乙烯释放量提高将近6倍，这可能是缺钾抑制棉花幼苗根系生长的重要原因之一。