为减轻烟嘧磺隆对甜玉米(Zea mays L. seccharata Sturt)的药害作用,探究甜玉米幼苗抗氧化系统对烟嘧磺隆胁迫的响应机制,本研究以一对甜玉米姊妹系(对烟嘧磺隆表现耐药性的甜玉米自交系HK301和对烟嘧磺隆表现敏感的甜玉米自交系HK320)为试材,研究烟嘧磺隆胁迫对不同耐药性甜玉米品种氧化压力、抗氧化酶、抗氧化系统非酶类物质和抗氧化酶关键基因表达量的影响。结果表明,烟嘧磺隆胁迫后,与对照(HK301-CK)相比,HK301的超氧阴离子自由基( O 2 - · )产生速率、过氧化氢(H₂O₂)含量和丙二醛(MDA)含量先增加后减少,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、单脱氢抗坏血酸还原酶(MDHAR)、脱氢抗坏血酸还原酶(DHAR)、谷胱甘肽还原酶(GR)活性均呈先升高后降低的趋势,抗坏血酸(AsA)含量、脱氢抗坏血酸(DHA)、还原型谷胱甘肽(GSH)含量先增加后减少,氧化型谷胱甘肽(GSSG)含量持续增加,抗坏血酸氧化还原状态(AsA/DHA比值)显著降低,谷胱甘肽氧化还原状态(GSH/GSSG比值)无显著差异。与对照(HK320-CK)相比,HK320的 O 2 - · 产生速率和H₂O₂含量显著增加, CAT、APX、DHAR、GR活性先升高后下降,SOD、MDHAR活性和GSH含量、GSH/GSSG 比值、AsA/DHA 比值呈下降趋势,DHA含量持续增加,GSSG含量无显著差异。烟嘧磺隆胁迫后,相较于HK320,HK301显著上调了SOD、CAT、APX、MDHAR、DHAR和GR基因的相对表达量。综合分析显示,不同耐药性甜玉米幼苗通过调节体内抗氧化物质含量和酶活性来清除活性氧,从而提高幼苗对除草剂的耐药性。本研究为揭示烟嘧磺隆胁迫下甜玉米幼苗抗氧化系统的代谢机制提供了理论依据。

Sucrose-phosphate synthase (SPS) from mature apple (Malus domestica Borhk. cv. Gala) leaves was purified 34-fold to a final specific activity of 15.3 μmol mg protein h. The enzyme showed hyperbolic saturation kinetics for both fructose-6-phosphate (F6P) (Km= 0.36 mM) and uridine-5'-diphosphoglucose (UDPG) (Km = 6.49 mM). Glucose-6-phosphate (G6P) was found to be an activator of apple SPS, and the activation was dependent upon the F6P concentration. At a concentration of 2 mM, G6P significantly decreased the Km for F6P and increased SPS activity. However, higher concentrations of G6P did not further stimulate SPS activity. In contrast to SPS from other plant species, inorganic phosphate (Pi) had little or no inhibitory effect on apple SPS. The apple leaf enzyme was inhibited 7-10% by 10 mM Pi when F6P concentrations were in the range of 2-10 mM. We observed that sorbitol-6-phosphate, an intermediate metabolite in sorbitol biosynthesis, was a competitive inhibitor of SPS with a Ki of 1.83 mM. Sorbitol-6-phosphate also inhibited G6P activation of SPS. Our results suggest that sucrose biosynthesis may be altered by the products of sorbitol biosynthesis in apple leaves.

Although graphene oxide (GO) has extensive recognized application prospects in slow-release fertilizer, plant pest control, and plant growth regulation, the incorporation of GO into nano herbicides is still in its early stages of development. This study selected a pair of sweet corn sister lines, nicosulfuron (NIF)-resistant HK301 and NIF-sensitive HK320, and sprayed them both with 80 mg kg of GO-NIF, with clean water as a control, to study the effect of GO-NIF on sweet corn seedling growth, photosynthesis, chlorophyll fluorescence, and antioxidant system enzyme activity. Compared to spraying water and GO alone, spraying GO-NIF was able to effectively reduce the toxic effect of NIF on sweet corn seedlings. Compared with NIF treatment, 10 days after of spraying GO-NIF, the net photosynthetic rate (A), stomatal conductance (G), transpiration rate (E), photosystem II photochemical maximum quantum yield (F/F), photochemical quenching coefficient (q), and photosynthetic electron transfer rate (ETR) of GO-NIF treatment were significantly increased by 328.31%, 132.44%, 574.39%, 73.53%, 152.41%, and 140.72%, respectively, compared to HK320. Compared to the imbalance of redox reactions continuously induced by NIF in HK320, GO-NIF effectively alleviated the observed oxidative pressure. Furthermore, compared to NIF treatment alone, GO-NIF treatment effectively increased the activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in both lines, indicating GO induced resistance to the damage caused by NIF to sweet corn seedlings. This study will provides an empirical basis for understanding the detoxification promoting effect of GO in NIF and analyzing the mechanism of GO induced allogeneic detoxification in cells.© 2024. The Author(s).

The work explored sucrose metabolism in the leaves subtending the cotton boll (SBL) and its role in boll weight after waterlogging in cotton. Results showed that net photosynthesis rate (Pn), relative water content, contents of Chlorophyll a and Chlorophyll b, initial ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) activity and cytosolic fructose-1, 6-bisphosphatase (cy-FBPase) activity decreased with waterlogging in the SBL on fruiting branches 2-3 (FB2-3) and FB6-7. Activities of sucrose synthase (SuSy) and sucrose phosphate synthase (SPS) increased to the maximum up to 6 days of waterlogging then decreased with prolonged waterlogging. Rubisco activation and specific leaf weight increased and gene expressions of SuSy, SPS and rubisco activase (RCA) were all up-regulated with the duration of waterlogging, especially for the SBL on FB6-7. The induction of activity and gene expression of SuSy was most significant indicating its crucial role in sucrose metabolism after waterlogging. For the SBL in the later period of boll development on upper FB10-11 and FB14-15, the pattern seemed opposite to that of FB2-3 and FB6c7 as compensation effect in vegetative growth existed. Correlation analysis revealed that initial Rubisco activity and cy-FBPase activity were the main limitation to Pn reduction after waterlogging. Reduction in Pn, sucrose transformation rate and initial Rubisco activity directly decrease boll weight in waterlogged cotton. Besides the role in sucrose metabolism after waterlogging, SuSy also had a positive significant correlation with the duration of rapid-accumulation period for seed fiber weight (P<0.05). These findings elucidated mechanisms to waterlogging that affected seed fiber weight, which resulted from alteration in carbohydrates, enzymes and genes. Copyright © 2014. Published by Elsevier Ireland Ltd.

Herbicides are pesticides used to eradicate unwanted plants in both crop and non-crop environments. These chemistries are toxic to weeds due to inhibition of key enzymes or disruption of essential biochemical processes required for weedy plants to survive. Crops can survive systemic herbicidal applications through various forms of detoxification, including metabolism that can be enhanced by safeners. Field studies were conducted near Louisville, Tennessee and Painter, Virginia to determine how the herbicides mesotrione, topramezone, nicosulfuron, and atrazine applied with or without the safener isoxadifen-ethyl would impact the nutritional quality of "Incredible" sweet corn ( Zea mays L. var. rugosa). Several herbicide treatments increased the uptake of the mineral elements phosphorus, magnesium, and manganese by 8-75%. All herbicide treatments increased protein content by 4-12%. Applied alone, nicosulfuron produced similar levels of saturated, monounsaturated, and polyunsaturated fatty acids when compared to the nontreated check, but when applied with isoxadifen-ethyl, fatty acids increased 8 to 44% relative to the check or control. Nicosulfuron plus isoxadifen-ethyl or topramezone or the combination of all three actives increased the concentrations of fructose and glucose (40-68%), whereas reducing levels of maltose or sucrose when compared to the nontreated check (-15 to -21%). Disruptions in biochemical pathways in plants due to the application of herbicides, safeners, or other pesticides have the potential to alter the nutrient quality, taste, and overall plant health associated with edible crops.

Sucrose phosphate synthase (SPS; EC 2.4.1.14) and sucrose synthase (SS; EC 2.4.1.13) are key enzymes in the synthesis and breakdown of sucrose in sugarcane. The activities of internodal SPS and SS, as well as transcript expression were determined using semi-quantitative RT-PCR at different developmental stages of high and low sucrose accumulating sugarcane cultivars. SPS activity and transcript expression was higher in mature internodes compared with immature internodes in all the studied cultivars. However, high sugar cultivars showed increased transcript expression and enzyme activity of SPS compared to low sugar cultivars at all developmental stages. SS activity was higher in immature internodes than in mature internodes in all cultivars; SS transcript expression showed a similar pattern. Our studies demonstrate that SPS activity was positively correlated with sucrose and negatively correlated with hexose sugars. However, SS activity was negatively correlated with sucrose and positively correlated with hexose sugars. The present study opens the possibility for improvement of sugarcane cultivars by increasing expression of the respective enzymes using transgene technology.© 2010 German Botanical Society and The Royal Botanical Society of the Netherlands.

Aluminium (Al) toxicity is a major chemical constraint limiting plant growth and production on acidic soils. Melatonin (N-acetyl-5-methoxytryptamine) is a ubiquitous molecule that plays crucial roles in plant growth and stress tolerance. However, there is no knowledge regarding whether melatonin is involved in plant responses to Al stress. Here, we show that optimal concentrations of melatonin could effectively ameliorate Al-induced phytotoxicity in soybean (Glycine max L.). The concentration of melatonin in roots was significantly increased by the 50μM Al treatment. Such an increase in endogenous melatonin coincided with the upregulation of the gene encoding acetyltransferase NSI-like (nuclear shuttle protein-interacting) in soybean roots. Supplementation with low concentrations of melatonin (0.1 and 1μM) conferred Al resistance as evident in partial alleviation of root growth inhibition and decreased H2O2 production: in contrast, high concentrations of melatonin (100 and 200μM) had an opposite effect and even decreased root growth in Al-exposed seedlings. Mitigation of Al stress by the 1μM melatonin root treatment was associated with enhanced activities of the antioxidant enzymes and increased exudation of malate and citrate. In conclusion, melatonin might play a critical role in soybean resistance to Al toxicity.