Drought stress during soybean seed filling affects storage compounds through regulation of lipid and protein metabolism

Soybean seeds have high lipid and protein contents. Adverse environmental conditions restrict seed yield and quality. We examined the changes in storage compounds caused by drought stress from R5 stage (beginning seed growth stage). Under drought stress, contents of lipid in seed were remarkably low compared to control at 24 and 29 days after treatment. Protein contents in seed were immediately decreased after water deficit treatment. On the other hand, soluble sugar contents in seed were increased by drought stress. Drought stress decreased the expression of genes involved in lipid biosynthesis (PK, BCCP2, and KAS1) and increased the genes expression involved in lipid degradation (ACX2, MS, and PEPCK). These results suggest that the increasing of sugar content in seed under drought stress was complemented by degradation of lipids. The expressions of genes encoding storage protein (Gy4 and β-conglycinin) were also decreased by drought stress. This study showed how drought stress during seed filling affects seed quality, especially lipid and protein contents, that may facilitate further research on seed storage compounds metabolism under environmental stresses.     

Management of genetically modified herbicide-tolerant sugar beet for spring and autumn environmental benefit

When used in genetically modified herbicide-tolerant (GMHT) crops, glyphosate provides great flexibility to manipulate weed populations with consequences for invertebrates and higher trophic levels, for example birds. A range of timings of band and overall spray treatments of glyphosate to GMHT sugar beet were compared with a conventional weed control programme in four field trials over 2 years. Single overall sprays applied between 200 and 250 accumulated day degrees (above a base air temperature of 3 degrees C; degrees Cd) and band applied treatments applied at 10% or 20% ground cover within the crop rows generally gave significantly greater weed biomass and seed rain than conventional treatments, while later band sprays (more than 650 degrees Cd) reduced seed return. Two overall sprays of glyphosate produced low weed biomass and generally lowest seed return of all treatments but tended to give some of the highest yields. However, the early overall sprays (200-250 degrees Cd) and band sprays gave as good or better yields than the conventional and were generally equivalent to the two overall-spray programme. Viable seeds in the soil after the experiment were generally higher following the early overall (200-250 degrees Cd) and the band spray treatments than following the conventional. The results show that altered management of GMHT sugar beet can provide alternative scenarios to those of the recent Farm Scale Evaluation trials. Without yield loss they can enhance weed seed banks and autumn bird food availability compared with conventional management, or provide early season benefits to invertebrates and nesting birds, depending on the system chosen. Conventional weed control does not have the flexibility to enable these scenarios that benefit both agriculture and environment, although there may be some options for increasing weed seed return in autumn.     

Exogenously applied glycinebetaine enhances seed and seed oil quality of maize (Zea mays L.) under water deficit conditions

A field trial was carried out to appraise up to what extent exogenous application of a potential osmoprotectant, glycinebetaine (GB), could ameliorate the inhibitory effects of shortage of water on maize seed and seed oil composition and oil antioxidant potential. Two maize cultivars, Agaiti-2002 (drought tolerant) and EV-1098 (drought sensitive), were exposed to drought treatments at the vegetative growth stage. Both the maize cultivars used in the present study are being widely cultivated in Pakistan and have been an important source of developing different maize hybrids. Two levels of glycinebetaine (0 or 30 mM) were foliar-applied at the vegetative stage. Water stress reduced the kernel sugar, oil, protein, moisture contents and most of the seed micro- and macro-nutrients analyzed of both maize cultivars, but it increased the contents of seed fiber and ash contents. Among different seed oil un-saturated fatty acids, water stress increased the oil oleic acid contents with a decrease in linoleic acid contents, which resulted in increased oil oleic/linoleic ratio of both maize cultivars. However, no variation was observed in oil stearic and palmitic acid contents due to water stress. A considerable increase in seed oil α-, γ-, δ- and total tocopherols and flavonoids was observed in both maize cultivars. However, oil phenolic content and 1,1′-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging activity decreased. Foliar-applied GB significantly increased the contents of seed sugar, oil, protein, moisture, fiber, ash, GB contents and micro- and macro-nutrients of both maize cultivars under well irrigated and water deficit conditions. Furthermore, exogenous application of GB increased the oil oleic and linoleinic acid contents. All different lipophilic compounds estimated in the seed oil increased due to foliar applied GB. Furthermore, GB also increased seed oil antioxidant activity appraised in terms of oil DPPH free radical scavenging activity. By summarizing the results, it seemed that exogenously applied GB remained in intact form until later stages of growth and counteracted the inhibitory effects of water deficit on seed and seed oil composition similarly of both maize cultivars.     

Brassinolide alleviates salt stress and increases antioxidant activity of cowpea plants (Vigna sinensis)

Soil salinity is one of the most severe factors limiting growth and physiological response in Vigna sinensis plants. Plant salt stress tolerance requires the activation of complex metabolic activities including antioxidative pathways, especially reactive oxygen species and scavenging systems within the cells which can contribute to continued growth under water stress. The present investigation was carried out to study the role of brassinolide in enhancing tolerance of cowpea plants to salt stress (NaCl). Treatment with 0.05?ppm brassinolide as foliar spray mitigated salt stress by inducing enzyme activities responsible for antioxidation, e.g., superoxide dismutase, peroxidase, polyphenol oxidase, and detoxification as well as by elevating contents of ascorbic acid, tocopherol, and glutathione. On the other hand, total soluble proteins decreased with increasing NaCl concentrations in comparison with control plants. However, lipid peroxidation increased with increasing concentrations of NaCl. In addition to, the high concentrations of NaCl (100 and 150?mM) decreased total phenol of cowpea plants as being compared with control plants. SDS-PAGE of protein revealed that NaCl treatments alone or in combination with 0.05?ppm brassinolide were associated with the disappearance of some bands or appearance of unique ones in cowpea plants. Electrophoretic studies of ??-esterase, ??-esterase, polyphenol oxidase, peroxidase, acid phosphatase, and superoxide dismutase isoenzymes showed wide variations in their intensities and densities among all treatments.     

Drought resistance in rice seedlings conferred by seed priming

Seed priming is a method by which seeds are subjected to different stress conditions to impart stress adaptation in seedlings germinating and growing under stressful situations. Drought stress is a major reason behind failure of crops. We studied the effects of hydropriming, dehydration priming (induced by PEG), and osmopriming (induced by NaCl and KH₂PO₄) on subsequent germination, growth and anti-oxidant defense mechanisms of 2-week-old rice seedlings under continuing dehydration stress. Unprimed seeds grown in PEG showed significantly lower germination and growth along with significantly higher reactive oxygen species (ROS) and lipid peroxidation levels. Among the priming methods, 5 % PEG priming was found to be the best in terms of germination and growth rate along with the lowest amount of ROS and lipid peroxidation (malondialdehyde [MDA]) values. MDA levels were reduced significantly by all of the priming methods. Hence, reduction of lipid peroxidation may be a key factor underlying the drought tolerance produced by the priming treatments. Glutathione peroxidase (GPX) activity seemed to bear an excellent correlation with oxidative stress resistance through seed priming. The PEG priming produced minimum peroxidative damage and superior germination and growth rate along with efficient GPX activity, overexpressed MnSOD and maintenance of HSP70 expression in normal as well as in drought condition. Therefore, in PEG-primed seeds the existence of robust protective mechanisms is definitely indicated.     

Changes of antioxidants levels in two maize lines following atrazine treatments.

Growth and antioxidants levels of shoot of 10-d-old maize lines (Zea mays L. Hybrid 351 and Giza 2) differentially responded to atrazine treatment at the recommended field dose (RFD) during the following 20 d. Atrazine significantly reduced shoot fresh and dry weights but significantly accumulated H(2)O(2), lipid peroxides and carbonyl groups in Giza 2 during the whole experiment; an effect that prolonged with either elapse of time or increasing the herbicide dose. Meanwhile, ascorbic acid (AsA) and reduced glutathione (GSH) contents were significantly decreased along with significant inhibitions in activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.7), guaiacol peroxidase (GPX; EC 1.11.1.7), and glutathione-S-transferase (GST; EC 2.5.1.18). Similar responses were observed in Hybrid 351 only during the first 12 d, and seemed to be overcome thereafter. These findings indicate an induced oxidative stress in maize following atrazine treatments. Such state appeared to be counterbalanced in Hybrid 351 but continued in Giza 2 concluding Giza 2 as more susceptible to atrazine than Hybrid 351. Therefore, the differential susceptibility of Giza 2 to atrazine is related to deficiency in antioxidant levels.     

Exogenous application of spermine and putrescine mitigate adversities of drought stress in wheat by protecting membranes and chloroplast ultra-structure

Polyamines (PAs) are positively charged molecules known to mitigate drought stress; however, little is known about their mechanism of alleviating drought stress. We investigated the effects of PAs exogenously applied as a seed primer and as a foliar spray on the growth, membrane stability (MS), electrolyte leakage (EL), Na+ and K+ cations, reactive oxygen species (ROS), catalase (CAT; EC 1.11.1.6) and guaiacol peroxidase (GPX; EC 1.11.1.7) activity and chloroplast ultra-structure in wheat (Triticum aestivum L.; cv. Sakha-94) under drought stress. Three PA solutions, namely, putrescine, spermine and a mixture of the two (Mix), were each applied at a concentration of 100 µM. Our study demonstrated that the retardation of chlorophyll loss and elevation of Rubisco levels were involved in PA-enhanced growth under drought stress. These relationships were mainly reflected in elevated fresh weight and dry weight in response to foliar spraying with all PA solutions and seed priming with the Mix solution. The elevated growth seemed to be due to increased photosynthetic pigments, protein and Rubisco. In contrast, drought decreased growth, photosynthetic pigments, protein and Rubisco. MS was enhanced by PAs applied as a seed primer or foliar spray, as shown by clear reductions in EL %, malondialdehyde (MDA) content and the Na+/K+ ratio as well as reduced ROS markers and elevated CAT (but not GPX) activity. Further study showed that the Mix solution of PAs, applied either during seed priming or as a foliar spray, improved chloroplast ultra-structure, suggesting that improvements in Rubisco and photosynthetic pigments were involved in PA maintenance of chloroplast stability. Therefore, the present study showed that elevated CAT activity is the main mechanism through which PAs reduce ROS and MDA, thereby improving MS and protecting mesophyll cells structurally and functionally under drought stress in wheat.     

Influence of exogenously applied paclobutrazol on some physiological traits and growth of Stevia rebaudiana under in vitro drought stress

This investigation was carried on to find out the changes occurred in Stevia rebaudiana in response to paclobutrazol (PBZ; 0–4 mg L^?1) treatment and drought stress. Polyethylene glycol (PEG; 0–6 % w/v) was used to stimulate drought stress. Drought stress reduced fresh and dry weight, water content, chlorophylls, carotenoids, anthocyanins, water soluble carbohydrates, reducing sugar and proline amounts. Electrolyte leakage, MDA, α-tocopherol and glycine betaine contents increased in drought-stressed plants. The activity of P5CS and PDH enzymes and protein content showed no significant changes under drought stress. PBZ (with or without PEG) treatments decreased fresh and dry weight and water content. In PBZ-treated plants, less pigments was damaged by drought stress. PBZ treatment reduced the negative effect of drought stress on lipid peroxidation which resulted in lower electrolyte leakage and MDA content, compared to the same PEG level without PBZ. PBZ (with or without PEG) treatments increased glycine betaine, α-tocopherol, proline and protein contents. The amount of water soluble carbohydrates, reducing sugar and activity of P5CS and PDH were not affected by PBZ treatments. SDS-PAGE analysis revealed that drought stress increased a 25 kD protein with a critical function in plant development under stresses. According to the results, PEG provoked a severe drought stress in S. rebaudiana that could partly be restored by PBZ treatment.     

保水技术对干旱胁迫下桔梗种子萌发及幼苗生长和生理特征的影响

以完整饱满的桔梗种子为材料,采用沙培控水方法进行盆栽实验,在沙粒(500g/盆)中分别均匀混入不同浓度梯度的保水剂(SAP)、保水剂与Na基膨润土(SAP+Na)、保水剂与Ca基膨润土(SAP+Ca)共3种保水处理技术,研究了不同保水技术对桔梗种子萌发以及幼苗生长、抗旱生理指标的影响。结果显示:1g SAP、(1+9)~(1.5+2)g SAP+Na、(1+9)g SAP+Ca均可显著提高桔梗种子的萌发,促进根系的生长速率,增加叶片中的相对含水量,增强叶片SOD、CAT活性,提高叶片游离脯氨酸、可溶性多糖及可溶性蛋白含量,减少干旱胁迫对细胞膜的破坏,有效降低了相对电导率,同时,处理提高了叶片中叶绿素与类胡萝卜素含量,增强了叶片产生光合色素的能力,有效增加ASA、GSH的含量,从而可抵御干旱造成的氧化胁迫,但随着混施浓度的增大,桔梗叶面抵御干旱胁迫的能力则会下降。研究表明,混施一定浓度SAP、SAP+Na和SAP+Ca可有效提供桔梗种子萌发所需适宜环境,减轻干旱胁迫对桔梗幼苗的伤害,且保水剂中混施Na基膨润土或者Ca基膨润土比单纯施保水剂效果更加明显。     

Boron induced changes in biochemical constituents,enzymatic activities,and growth performance of wheat

The present study investigates how excess boron (B) affects and alters the biochemical constituents and enzymatic activities of wheat (Triticum aestivum var. ‘Raj 4037’), consequently leading to reduced plant growth and yield. Plants were raised in soils supplemented with various concentrations of B (0, 1, 2, 4, 8, 16, and 32 µg B g^?1 soil). Biochemical constituents including soluble leaf protein contents, total phenol contents, soluble sugar contents, proline contents, enzymatic activities of peroxidase (POX), and nitrate reductase (NR) were analyzed. In addition, growth parameters namely shoot–root length, shoot–root fresh and dry weight, seed number and seed weight were analyzed to assess the impact of B toxicity. Results indicate that change in biochemical constituents were correlated with B treatments. Boron concentrations beyond 4 µg g^?1 significantly increased soluble leaf protein contents, total phenol contents, soluble sugar contents, and proline contents. The POX activity was found to be positively correlated with B treatments. B significantly affects nitrogen metabolism and nitrate accumulation which is reflected by the downregulation of NR activity at higher B concentrations. B induced changes in physiological parameters of the plant which subsequently led to the reduction in growth, biomass production, and yield attributes. Out of the various concentrations of B, 8 µg g^?1 was moderately toxic while 16 and 32 µg g^?1 generated high toxicity and induced B stress response to confer tolerance in wheat. Further, a possible mechanism of B toxicity response in wheat is suggested.     

Physiological and biochemical changes in different sugar beet genotypes infected with root-knot nematode

Ten genotypes of sugar beet plant either monogerm or multigerm seeds were screened under greenhouse conditions for both susceptibility and biochemical reaction to root-knot nematode (RKN) Meloidogyne incognita. All the tested genotypes were susceptible to nematode infection according to the number of root galls and gall indices. All infected genotypes exhibited significant reduction in chlorophyll a, b and carotenoids compared to non-infected ones. The total indole acetic acid and total phenolic compounds contents (mean of both shoot and root) increased significantly in most infected genotypes compared to non-infected genotypes except Disk-01-99 and Monte Rosa as well as LP16 and LP15 genotypes, respectively. Also, total polyamine contents (putrescine, spermidine and spermine) showed significant increases in response to infection with nematodes in all genotypes. The same trend was observed in lipid peroxidation expressed with malondialdehyde content in all tested genotypes. Activities of polyphenol oxidase, peroxidase, superoxide dismutase and catalase enzymes were also induced in most infected genotypes compared with non-infected genotypes. Generally, infection with RKNs induced the appearance of new protein bands at molecular masses 303, 288, 42 and 37?KDa in all infected genotypes. The differentiation in the appearance and/or disappearance of protein bands according to susceptibility to infection reflects the variation between genotypes in defense against infection.     

Changes in total nitrogen, soluble protein, and peroxidases in the expanding leaf zone of eastern cottonwood

Nitrogen content and soluble protein and anodal peroxidase banding in acrylamide gel changed with leaf and internode development in the expanding leaf zone of eastern cottonwood (Populus deltoides Bartr.). Nitrogen per unit leaf area was high near the apex and decreased to a constant value at the sixth node below it. Soluble protein banding was qualitatively similar for leaves and internodes in this zone, but anodal peroxidases differed between leaves and internodes. The major leaf peroxidase band was absent from the second leaf below the apex but present in the fourth and sixth leaves; its appearance and intensification seemed to parallel the development of photosynthetic activity. The major internode peroxidase band was present in the apex, second, fourth, and sixth internodes, and intensified during internodal development. It is suggested that these two “isoenzymes” may have different functions in vivo.     

Ultraviolet-B and water stress effects on growth,gas exchange and oxidative stress in sunflower plants

The effects and interaction of drought and UV-B radiation were studied in sunflower plants (Helianthus annuus L. var. Catissol-01), growing in a greenhouse under natural photoperiod conditions. The plants received approximately 1.7 W m(-2) (controls) or 8.6 W m(-2) (+UV-B) of UV-B radiation for 7 h per day. The UV-B and water stress treatments started 18 days after sowing. After a period of 12 days of stress, half of the water-stressed plants (including both UV-B irradiated or non-irradiated) were rehydrated. Both drought and UV-B radiation treatments resulted in lower shoot dry matter per plant, but there was no significant interaction between the two treatments. Water stress and UV-B radiation reduced photosynthesis, stomatal conductance and transpiration. However, the amplitude of the effects of both stressors was dependent on the interactions. This resulted in alleviation of the negative effect of drought on photosynthesis and transpiration by UV-B radiation as the water stress intensified. Intercelluar CO(2) concentration was initially reduced in all treatments compared to control plants but it increased with time. Photosynthetic pigments were not affected by UV-B radiation. Water stress reduced photosynthetic pigments only under high UV-B radiation. The decrease was more accentuated for chlorophyll a than for chlorophyll b. As a measure for the maximum efficiency of photosystem II in darkness F (v)/F (m) was used, which was not affected by drought stress but initially reduced by UV-B radiation. Independent of water supply, UV-B radiation increased the activity of pirogalol peroxidase and did not increase the level of malondialdehyde. On the other hand, water stress did not alter the activity of pirogalol peroxidase and caused membrane damage as assessed by lipid peroxidation. The application of UV-B radiation together with drought seemed to have a protective effect by lowering the intensity of lipid peroxidation caused by water stress. The content of proline was not affected by UV-B radiation but was increased by water stress under both low and high UV-B radiation. After 24 h of rehydration, most of the parameters analyzed recovered to the same level as the unstressed plants.     

Mycorrhizal influence on protein and lipid of durum wheat grown at different soil phosphorus levels

 Root colonization by arbuscular mycorrhizal fungi (AMF) may affect protein and lipid composition of plants by altering P nutrition or by eliciting other metabolic responses in the host plant. This study was conducted to determine the effects of an AMF and soil P on seed protein and lipid contents and yield of two genotypes of durum wheat (Triticum durum L.). Plants were grown in a greenhouse using soil: sand mixes with different levels of P, and with or without the AMF Glomus mosseae [(Nicol. and Gerd.) Gerd. and Trappe]. Percentage AMF root colonization decreased as P added to soil increased. The wheat genotype CR057 had higher AMF root colonization but lower seed P and protein concentrations than CR006. Without added soil P, protein concentration was significantly lower and lipid concentration and seed dry weight higher in arbuscular mycorrhizal (AM) than in nonAM plants. Seed lipid and protein contents were highly correlated with P content of plants. In nonAM plants, seed lipid and protein contents were low with no added soil P and did not differ with added soil P. Seed protein/lipid (Pro/L) concentration ratios of AM plants were higher than those of nonAM plants only when no P was added to the soil. The data indicate different patterns of seed P accumulation and different relationships between seed P and protein and lipid in AM and nonAM plants. Thus, both the presence and degree of AMF root colonization affected seed lipid metabolism in these durum wheat genotypes. Accepted: 18 May 1999     

The effect of iprodione on sclerotium germination, root infection and mycelial spread of Sclerotium cepivorum in salad onions

Iprodione seed treatment at 125 g a.i./kg seed and stem base sprays at 0–3 and 0.125 g a.i./m row delayed the appearance and reduced the incidence of stem base symptoms and root infection with Sclerotium cepivorum in autumn- and spring-sown salad onions. Viability of sclerotia was unaffected by the treatments but their germination was delayed. The spread of mycelium between plants was suppressed but growth of hyphae within infected roots was much less affected.     

干旱胁迫对远志种子萌发及幼苗生长和生理特性的影响

以远志(Polygala tenuifolia Willd.)为研究对象,采用不同浓度(2.5%~25%)聚乙二醇(PEG-6000)模拟不同程度的干旱胁迫,探讨干旱胁迫对远志种子萌发及幼苗生理生化特性的影响。结果表明:(1)随着干旱胁迫强度的增加,远志种子的发芽启动时间推迟,发芽率、发芽势、发芽指数和活力指数降低,但种子发芽率在2.5%~15%PEG胁迫下与对照无显著性差异,而在20%PEG胁迫下均显著低于对照,在25%PEG胁迫下种子不能萌发;在干旱胁迫条件下,远志幼苗生物量降低,胚芽生长受到显著抑制,胚根长度则先伸长后缩短。(2)远志幼苗叶绿素含量在2.5%~10%PEG范围内随胁迫强度的增加和时间的延长而持续上升,在15%和20%PEG胁迫下则表现为先上升后下降,在10%PEG胁迫处理第15天时含量最高,为对照的1.34倍。(3)幼苗叶片的游离脯氨酸、可溶性糖和可溶性蛋白含量随PEG胁迫强度的增加和时间的延长而增加,各指标均在20%PEG胁迫处理第15天时含量最高,分别为对照的1.99倍、1.53倍和1.50倍。(4)随着PEG胁迫时间的延长,远志幼苗叶片超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性先上升后下降,并在10%PEG胁迫处理第10天时活性最强;过氧化物酶(POD)活性随着胁迫时间的延长表现出先上升后下降又上升的特性,并在20%PEG胁迫处理第5天时活性最强;叶片丙二醛(MDA)含量在15%和20%PEG胁迫处理下持续上升,在2.5%~10%PEG胁迫范围内先上升后又有所下降。研究发现,远志种子在轻、中度干旱胁迫下仍可正常萌发,而且幼苗能通过调节自身生长、渗透调节物质含量和抗氧化酶活性主动适应干旱环境,对干旱环境表现出较好的适应能力。     

Tolerance of Mycorrhiza infected pistachio (Pistacia vera L.) seedling to drought stress under glasshouse conditions

The influence of Glomus etunicatum colonization on plant growth and drought tolerance of 3-month-old Pistacia vera seedlings in potted culture was studied in two different water treatments. The arbuscular mycorrhiza (AM) inoculation and plant growth (including plant shoot and root weight, leaf area, and total chlorophyll) were higher for well-watered than for water-stressed plants. The growth of AM-treated seedlings was higher than non-AM-treatment regardless of water status. P, K, Zn and Cu contents in AM-treated shoots were greater than those in non-AM shoots under well-watered conditions and drought stress. N and Ca content were higher under drought stress, while AM symbiosis did not affect the Mg content. The contents of soluble sugars, proteins, flavonoid and proline were higher in mycorrhizal than non-mycorrhizal-treated plants under the whole water regime. AM colonization increased the activities of peroxidase enzyme in treatments, but did not affect the catalase activity in shoots and roots under well-watered conditions and drought stress. We conclude that AM colonization improved the drought tolerance of P. vera seedlings by increasing the accumulation of osmotic adjustment compounds, nutritional and antioxidant enzyme activity. It appears that AM formation enhanced the drought tolerance of pistachio plants, which increased host biomass and plant growth.     

种子大小和干旱胁迫对辽东栎幼苗生长和生理特性的影响

在温室内遮阴条件下,设置80%、60%、40%和20%田间持水量(对照、轻度、中度和重度干旱)4个处理,研究种子大小和干旱胁迫对盆栽辽东栎幼苗生长和生理特性的影响。结果表明: 大种子(3.05±0.38 g)幼苗的单株叶面积、总干质量和根冠比在所有处理均显著大于小种子(1.46±0.27 g)幼苗,前者的株高、基径、叶片数、比叶面积、相对生长率和净同化率等生长参数在轻度、中度和重度干旱处理均不同程度大于后者。大种子幼苗叶片过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性均高于小种子幼苗,前者叶片丙二醛(MDA)、可溶性蛋白、游离脯氨酸含量和叶绿素总量在部分干旱处理显著大于后者。除根冠比外,其他生长参数均随干旱胁迫增强逐渐减小,重度干旱处理大、小种子幼苗总干质量分别比对照降低19.4%和20.0%。POD、CAT和SOD活性均随干旱胁迫增强先升后降,在中度干旱处理,大、小种子幼苗POD活性分别显著高于对照126.7%和142.1%,CAT活性分别显著高于对照170.0%和151.9%。在重度干旱处理,大、小种子幼苗MDA含量分别显著高于对照86.5%和68.9%。可溶性蛋白、游离脯氨酸含量和叶绿素总量均随干旱胁迫增强先升后降,在中度干旱处理,大、小种子幼苗可溶性蛋白含量分别显著高于对照320.7%和352.7%。辽东栎大种子幼苗可依赖其生长和生理方面的优势比小种子幼苗具有更强的干旱耐受性,在退化次生林人工辅助实生更新中应优先选用抗逆性更强的大种子幼苗。     

Fusion of small unilamellar vesicles with viable EDTA-treated Escherichia coli cells.

Fusion characteristics of EDTA-treated Escherichia coli cells with small unilamellar vesicles were investigated, using a membrane fusion assay based on resonance energy transfer. Ca2+-EDTA treatments of Escherichia coli O111:B4 (wild type), E. coli C600 (rough), and E. coli D21f2 (deep rough) which permeabilize the outer membrane by inducing the release of lipopolysaccharide and outer membrane proteins resulted in fusion activity of the intact and viable bacteria with small unilamellar vesicles. No fusion activity was observed when the EDTA treatment was omitted. Fusion could be elicited at low pH and by a combination of a higher pH and Ca2+. The low-pH-induced fusion was composed of a fast and a slow reaction. The latter and the Ca2+-induced fusion could be completely inhibited by trypsin treatments of the EDTA-treated cells, which also resulted in the simultaneous disappearance of two outer membrane protein bands (50 and 58 kilodaltons) and the appearance of proteins banding at 22, 52, and 54 kilodaltons. The most efficient fusion was obtained with negatively charged liposomes composed of cardiolipin. In contrast to the Ca2+-induced fusion, fusion was observed at low pH with small unilamellar vesicles containing lipids with decreased negative charge (phosphatidylserine). Fluorescent and phase-contrast microscopy revealed that essentially all bacteria were engaged in fusion. We propose that a Ca2+-EDTA treatment of E. coli cells results in the appearance of phospholipids and the exposure of a protein(s) in the outer leaflet of the outer membrane, both of which could mediate fusion with liposomes.     

Seed priming with boron improves growth and yield of fine grain aromatic rice

Boron (B) is amongst the important micronutrients required for rice from start till physiological maturity. This study was conducted to explore the role of boron application in seedling emergence, leaf appearance and elongation, chlorophyll content, water relations and yield related traits of fine rice. Boron was applied as seed priming. For priming seeds of fine rice cultivars Super Basmati and Shaheen Basmati were soaked in 0.001 and 0.01?% aerated B solutions (w/v); while untreated dry seeds and water soaked (hydropriming) seeds were taken as control. Substantial improvement in seedling emergence was noted by seed priming in 0.001 and 0.01?% solutions. Rate of leaf emergence and elongation and tiller appearance were also improved in seedlings raised from seeds primed in 0.001?% B solution in the tested cultivars. Likewise, leaf chlorophyll contents were significantly improved by B especially with 0.001?% concentration; as was the case for water relations of rice cultivars. At final harvest, all yield contributing parameters were improved by B priming. Increase in yield was due to decrease in panicle sterility by B treatments. A linear increase in leaf and grain B contents was observed with increase in concentration of B priming solution. Overall, B application at very low rate substantially improved seedling emergence, leaf appearance and elongation, tillering, chlorophyll, water relations and yield related traits resulting in better yield and grain B contents. In this regard, seed priming offers an effective and pragmatic way of B application.