Diclofop-methyl antagonism by broadleaf weed herbicides: the importance of leaf expansion rate

Avena saliva cv. Amuri and A. fatua were sprayed with diclofop methyl (1.0 kg a.i. ha^?1) alone and in combination with 2,4-D (1.1 kg a.i. ha^?1), bentazone (1.0 kg a.i. ha^?1), chlorsulfuron (15 g a.i. ha^?1) or dicamba (0.3 kg a.i. ha^?1). Effects of the herbicides on leaf extension rate during the first 8 to 10 days after spraying and subsequent growth (dry weight) after 57–75 days were determined by comparison with unsprayed plants. Diclofop-methyl applied alone did not cause a decrease in leaf extension rate of A. saliva or A. fatua until at least 4 days after spraying. All broadleaf weed herbicides in combination with diclofop-methyl caused a decrease in leaf extension rate of both species within 2 days of spraying. Ten days after spraying, leaf extension rates for plants sprayed with a broadleaf weed herbicide plus diclofopmethyl (all combinations) were lower than for unsprayed plants but greater than for plants sprayed with diclofop-methyl alone. With the exception of A. fatua sprayed with bentazone, long-term growth of plants sprayed with a broadleaf weed herbicide plus diclofop-methyl (all combinations) was lower than for unsprayed plants but greater than for plants sprayed with diclofop-methyl alone. Bentazone applied with diclofop-methyl caused a substantial decrease in leaf extension rate of A. fatua within 24 h of spraying but at harvest, dry weight of plants from this treatment was similar to or less than that for plants sprayed with diclofop-methyl alone. Application of diclofop-methyl with bentazone at a rate of 0.3 kg a.i. ha^?1 also caused a reduction in leaf extension rate of A. fatua within one day of spraying. At this rate of bentazone, dry weight of plants at harvest was intermediate to that of unsprayed plants and those sprayed with diclofop-methyl alone. It is proposed that decreased leaf expansion rate during the first few days afte spraying is the cause of broadleaf weed herbicide antagonism of diclofop-methyl.     

Abscisic acid as a protectant of Avena fatua L. against diclofop-methyl activity

The imposition of water stress before or al the time of spraying diclofop-methyl reduced efficacy against wild oat (Avena fatua L.). Similar reductions in herbicide performance were obtained by application of 20 μg of the methyl ester of abscisic acid (ABA) to plants with three to four leaves before spraying with I kg ha^?1 diclofop-methyl. Application of 40–100 μg ABA per plant effectively protected plants against damage from diclofop-methyl applied at 1 5–2 0 kg ha ^?1. The application of 20 μg ABA induced rapid stomatal closure and a reduction in leaf extension rate, which were sustained for 7–8 days after treatment. These changes were associated with an overall reduction in shoot growth. ABA-treated plants that were additionally sprayed with diclofop-methyl sustained ABA symptoms, but no additional weight loss or leaf chlorosis. The mechanism of the protective action of ABA on diclofop-methyl has not been determined.     

The response of resistant and susceptible plants to diclofop-methyl

Wild oat (Avena fatua L.) plants sprayed at the 2-or 3-leaf stages of growth with diclotop-methyl developed chlorosis over the entire leaf blade of all leaves. The leaves became necfrotic ⁷days after spraying Shool growth was inhibited. In wheat (Triticum aesicum L cv.Waldron) discrete chlorotic areas developed only where the herbicide convicted the 2nd or 3rd leaf with no visible injury so new growth uf'ter treutment. Growth inhibition of susceptible oat (Avena sativa L. cv. Garry) was sensitive to placement of diclutop-methyl near the upica and meristematic sites of the plant. Chlorosis and necrosis were independent of herbicide placement. Selective herbicide placement induced chlorosis only or both chlorosis and growth inhibition Root growth in wild oat and barley (Hordeum rulgare L. cv. Dickson) was strongly inhibited by 1–0 μM diclofop-methyl. Wild oat shoots were killed when seedlings were root-treated with 10 μM diclofop-melhyl. The 100 μM rool treatment killed barley shoots but only stunted the growth of wheat shoots by approximately 50%. In root-ireated wheat plants the shoots were turgid and developed a light purple colour, whereas in foliar-treated plants the shoots developed discrete chlorotic areas.     

The impact of foliar fertilizers on growth and biochemical responses of Thymus vulgaris to salinity stress

Salinity reduces plant biomass and may lead to death when severe. To cope with the negative effects of this stress, plant species present specific physiological or biochemical responses. In this work, we hypothesized that spraying salt-stressed thyme leaves with K⁺ and Ca²⁺ could mitigate the negative effects of salinity on plant growth and metabolism. To test this hypothesis, we grew thyme plants under salinity stress for two and four weeks before applying foliar sprays. Also, to test the effect of stress relief, treated plants were allowed two weeks of recovery after four weeks of salt stress. In general, after two and four weeks of salinity stress, the leaf fresh weight of thyme plants was reduced by 31 and 43%, respectively. Salinity also decreased the relative water content, water, and osmotic potentials and led to ion imbalances and nutrient deficiencies. Salinity altered concentration of some essential oils, but leaf antioxidant contents remained fairly stable, except for a significant increase for plants under NaCl?+?KCl two weeks after treatment. Our results indicated that stressed plants accumulated significantly more soluble sugars and amino acids in comparison with the control. Foliar sprays with KCl and CaCl₂ reversed the negative effects of salinity on plant biomass and induced the accumulations of compatible solutes. Moreover, concentrations of some essential oils and gallic acid increased in sprayed plants, but these effects were dependent on the type and duration of the treatment. Overall, spraying leaves with K⁺ and Ca²⁺ was able to mitigate salinity stress in Thymus vulgaris even during the recovery period.     

Red leaf blotch (Dactuliochaeta glycines) of soybeans (Glycine max) and its relationship to yield

Red leaf blotch of soybeans, caused by Dactuliochaeta glycines, was evaluated on soybean plants in field plots located in Zambia. Two experiments were conducted in each of two seasons. Experiment 1 had four cultivars that were either fungicide-sprayed or not sprayed. Disease severity was greatest on leaves at the lowest nodes from early vegetative through the reproductive growth stages. Area under the disease progress curve (AUDPC) values and percentage of nodes defoliated at growth stage R5 were significantly ( P  = 0.05) greater in unsprayed plots for all cultivars in both seasons. Yield losses ranged from 8 to 37% while reduced seed size ranged from 21 to 29% for the four cultivars. Number of pods per plant in fungicide-sprayed plots did not differ from those in unsprayed plots. However, the number of seeds per plant and seeds per pod were significantly ( P  = 0.05) greater in sprayed than unsprayed plots for some cultivars. In experiment 2, cultivar Tunia was either fungicide-sprayed at different times or not sprayed. The lowest attached leaf had the most variation in the amount of disease while ratings of the most median leaf in the canopy were generally less variable. The AUDPC values calculated from the lowest attached leaf, the mean of all attached leaves, and the median attached leaf differed significantly ( P  = 0.05) the number of times plants were sprayed with fungicide. Defoliation and vertical incidence of red leaf blotch from lower to higher nodes were significantly ( P  = 0.05) reduced in fungicide-sprayed plots in one season, but not the other. One thousand-seed weight and yield differed significantly ( P  = 0.05) with treatment as one application of triphenyltin acetate increased yields by 18% over unsprayed plots in season 1. One thousand-seed weight and yield, regressed on the AUDPC for the median leaf in the canopy, explained 92 and 72% of the variation, respectively.     

THE EFFECT OF MCPA ON THE AMINO ACID AND SUGAR COMPOSITION OF VICIA FABA LEAVES

Summary. The effect of spraying Vicia faba leaves with 5000 ppm MCPA is described. Three to 4 days after spraying, a marked increase (× 5 approx.) was found in the concentrations of leucine iso -leucine and valine in the leaves. No significant changes were detected in the other amino acids. Treatment with MGPA also caused a significant increase (× 4 approx.) in the glucose and fructose content of the leaves. Detached leaves (sprayed and unsprayed), when kept in a moist atmosphere for 3–4 days, exhibited very similar increases in amino acids and sugars to sprayed intact plants. Experiments using ¹⁴CO₂ revealed that in short term photosynthesis (30 min) of sprayed and unsprayed plants, 80–90% of the radioactivity was incorporated in sucrose, with about 5% in each of glucose and fructose. Over photosynthelic periods of 4 days, glucose and fructose were found to be almost as heavily labelled as sucrose in sprayed plants, but in the controls the distribution of radioactivity was similar to that in short term photosynthesis. It is suggested that the build up of amino acids and sugars in plants treated with MCPA is due to an interruption of the translocatory flow from the leaves, and that this build up of metabolites may be a contributory factor in the toxic action of this herbicide.
Effet du MCPA sur la composition en amino-acides et en sucre des feuilles de Vicia faba     

Field effectiveness of fosetyl-AI against citrus foot rot and brown rot1

The effectiveness of fosetyl-A1 against citrus foot rot caused by Phytophthora citrophthora has been evaluated in a 25-year-old orchard of sweet orange cv. Tarocco, showing severe symptoms of the disease and in a 10-year-old orchard of the clementine-type mandarin cv. Monreal, apparently healthy. All the trees were grafted on sour orange. In both orchards, three sprays at 200 g a.i. per 100 1 were applied in May, July and September for 3 years. The results were evaluated on the basis of yield and fruit quality. Trees of cv. Tarocco had yield increased by 25–44% whereas cv. Monreal yielded 3–16% higher than the unsprayed trees. Fruits of orange cv. Tarocco were collected from trees sprayed with fosetyl-A1 and plunged in a water suspension of P. citrophthora. Fruits treated 11 days before inoculation showed an infection rate of 8.7%) whereas those unsprayed were 77% infected. Fruits inoculated 21 days after the treatment with fosetyl-A1 were 32% infected whereas those unsprayed were 91%, infected. In other trials, trees of volkamer lemon were sprayed with a conidial and mycelial suspension of P. citrophthora at different times after application of fosetyl-A1. The number of infected fruits and leaves in the unsprayed trees was very high (up to total leaf drop) and decreased sharply with the number of sprays (1 to 3).     

Effect of 2,4-D on the water-soluble carbohydrate content of ragwort (Senecio jacobaea L.) leaves

Leaves of Senecio jacobaea plants sprayed with 2,4-D had a higher water-soluble carbohydrate (WSC) content than unsprayed leaves 9–14 days after spraying. Insofar as WSC is a measure of palatability, this implies an increased risk of Senecio poisoning in grazing cattle for more than 14 days after spraying with growth regulator herbicides. Total unsaturated pyrrolizidine alkaloid content may also be increased by 2,4-D, making the plant more toxic.     

Water utilization by S-ethyl dipropylthiocarbamate treated wheat

Wheat (Triticum aesticum L. var. Holley) was grown in 0.5 Hoaglands complete mineral nutrient solution containing sub-toxic concentrations of S-ethyl dipropyl-thiocarbamate (EPTC) (0, 0.0625, 0.125, 0.25, or 0.5mg/1). Total fresh and dry plant weights per pot decreasedas EPTC concentration increased. Leaf fresh and dry weight per pot decreased as EPTC concentration increased. Root fresh weight per pot was not greatly influenced by EPTC and dry weight per pot was statistically significantly decreased at the 0.5 mg/l EPTC concentration. Total plant water utilization and leaf water contents (mg/g DW) decreased as EPTC concentration increased, but evapotranspiration (ml/g FW or DW) per unit leaf tissue was increased to ca 145% of the untreated wheat. This increased evapotranspiration explains an EPTC induced accumulation of 14C-atrazine in leaves beyond the detoxification level which ultimately resulted in atrazine injury in EPTC pretreated plants.     

沙芦内含物PAAC对干旱胁迫下玉米幼苗叶片光合及蛋白氧化损伤的保护作用

采用沙培试验,培养期间用沙丘芦苇特有的多氨基芳香族化合物PAAC水溶液对培养的两种不同基因型玉米幼苗叶片进行喷施处理,研究幼苗叶片在正常供水和干旱胁迫下的相对含水量、光合作用、叶绿素荧光等参数的变化趋势。确定这些生理指标在评价作物抗旱性方面的作用,并与甜菜碱溶液喷施处理的作物参比,研究该内含物对植物蛋白氧化损伤的影响。结果表明:PAAC溶液能够明显地降低干旱下植物叶片蛋白质中羰基含量的上升,即该内含物能够有效地减弱干旱胁迫下植物蛋白氧化损伤程度,RWC相对较高,说明PAAC一定程度上降低水分的散失。当植物受到中度干旱胁迫时,PAAC显著地减缓玉米叶片光合速率的下降,同时Fv/Fm、qP、ETR等叶绿素荧光参数数值也明显高于同期的对照,表明PAAC具有保护类囊体膜上PSⅡ的光合学活性的作用,一定程度上增强了植物的抗旱能力。     

Factors affecting glyphosate activity in Imperata cylindrica (L.) Beauv. and Cyperus rotundus L. II: effect of shade

Imperata cylindrica and Cyperus rotundus were grown under three different light regimes; unshaded, 50% shade, and 75% shade and no shade plus 75% shade before and after spraying, (temporary shade) in a heated greenhouse. Six weeks after the start of the experimenis, glyphosate was applied to the plants at 0·2, 0·4 and 0·8 kg/ha (for Imperata) or 0·3, 0·6 and 1·2 kg/ha (for Cyperus). Glyphosate toxicity was enhanced as shade increased. In Imperata, all shade regimes at all rates of glyphosate eaused greater damage to the plants than the unshaded regime. The reduction in shoot dry weight, rhizome dry weight and total carbohydrate content of Imperate rhizotties at 75% continuous and temporary shaiie conditions, with the lowest rate of glyphosate, was almost twice as much as the reduction in the same features m the unshaded plants caused by the highest rate of glyphosate. In Cyperus. glyphosate at the intermediate and highest rates decreased the shoot dry weight at 75% continuous shade by 79% and 98% respectively. Plants in 50% shade were significantly affected only at the highest rate of glyphosate. Sprouting ability of the tubers al 75% continuous shade was inhibited when the tubers were replanted for recovery. Enhanced toxicity of glyphosate in reduced light intensity was attributed to the morphological changes in the nature of the leaves caused by shade.     

硼调控干旱胁迫下马铃薯生长发育及抗性的生理机制

为了探讨叶面喷施硼（Na2B4O7·10H2O溶液）对马铃薯植株在干旱胁迫下生长发育及抗性的影响及其生理机制,在甘肃省景泰县条山集团马铃薯种植基地,对中度干旱和轻度干旱处理的两垄地,每隔3m进行一个硼浓度（Na2B4O7·10H2O）喷施处理,浓度依次为0、10、20、30、40、60 g·L-1,每个浓度（3 m长）的喷施量为166．7 ml。结果表明：叶面喷施硼相对增加了干旱胁迫下马铃薯的块茎产量及生物量,使干旱胁迫下叶片含水量和色素含量下降幅度减小;叶面喷施硼还从整体上表现为抗氧化酶活性的提高,并抑制了超氧阴离子产生速率的增加。通过去花与不去花植株生长发育的比较,发现去花后马铃薯植株地上部分重和地下部分重均有所下降,但施硼相对提高了块茎产量及地下部分重。可见,叶面喷施硼能促进马铃薯植株在干旱胁迫下的生长发育,提高其抗旱性及块茎产量,且这种变化可能与其促进光合产物向地下部分输送密切相关。     

Detection of triazine and urea herbicide residues by various characteristics of oat seedlings in bioassays

Atrazine, simazine, diuron, and linuron applied to soil increased the percentage moisture of oat (Avena sativa L.) shoots in bioassays at the lowest dose tested of 0·25 ppm. Further increases occurred up to 2 ppm but at higher concentrations the percentage moisture decreased. At all doses of each herbicide, shoot dry weight was decreased. In oats grown on soil collected from a peach orchard which had received repeated annual applications of these herbicides, the percentage moisture of the oat shoots was higher than the control value whenever the oat dry weight was decreased and provided a method of residue detection as sensitive as dry weight measurements. Treatment of oats by soil application of the above herbicides in bioassays also caused increases in the electrical conductivity of an aqueous extract of the oat shoots per mg of dry weight and this characteristic was slightly more sensitive than dry weight in detecting herbicides in orchard soil. The conductivity of the extract per mg of water in the shoots, however, only increased as percentage moisture decreased. The weight of neutral water-soluble material in oat shoots decreased much more rapidly than dry weight in bioassays with standard herbicide concentrations. Determination of the weight of neutral water-soluble material in oat plants grown on orchard soil samples indicated the presence of herbicide residues in 50% of the cases in which residues were not detectable by dry weight. The weight of neutral material as a percentage of dry weight was almost as sensitive. Chemical analysis of soil in which oat plants had a decreased level of neutral water-soluble compounds indicated that this characteristic had a lower limit of detection for herbicide residues of approximately 0.10 ppm.     

Foliar spray of a cell wall protein fraction from the biocontrol agent <Emphasis Type="Italic">Pythium oligandrum</Emphasis> induces defence-related genes and increases resistance against Cercospora leaf spot in sugar beet

After a cell wall protein fraction (CWP) of Pythium oligandrum was sprayed on sugar beet leaves, we screened leaves for induced expression of defence-related genes and for resistance against Cercospora leaf spot. In a western blot analysis, the CWP was primarily retained on the surface of leaves without degradation for at least 48 h after spraying. In northern blot analyses, four defence-related genes (β-1, 3-glucanase, acidic class III chitinase, 5-enol-pyruvylshikimate-phosphate synthase and oxalate oxidase-like germin) were expressed more rapidly in CWP-treated leaves compared to control leaves treated with distilled water (DW). When CWP was applied to a suspension of cultured cells of sugar beet, an oxidative burst was observed that did not occur after the DW treatment. In growth chamber trials after inoculation with Cercospora beticola, the severity of Cercospora leaf spot was significantly reduced in CWP-treated plants compared to the DW-treated controls. In a field experiment, CWP treatment was also effective against the disease. CWP did not reduce growth rate of the pathogen in plate tests. The results together suggest that the CWP from P. oligandrum can be retained on the leaf surface and induce expression of disease resistance genes, thereby reducing Cercospora leaf spot on sugar beet.     

Factors affecting glyphosate activity in Imperata cylindrica (L) Beau, and Cyperus votundus L. I. Effect of soil moisture

Established Greenhouse grown plants of cogongrass Imperata cylindrica (L) Beauv.) and purple nutsedge (Cyperus rotundusL.) were given three different soil moisture regimes; field capacity, moderate stress and extreme stress, followed 6 weeks later by glyphosate [(N-phosphonomeihyl) glydne] applications to the shoots at 0.2,0.4 and 0.8 kg/ha for Imperata and 0.3,0.6 and 1.12 kg/ha for Cyperus. Field capacity watering stimulated most vegetative growth in hoth species. Glyphosate given at field capacity decreased shoot dry weight in both species, and rhizome length, rhizome dry weight and total carbohydrate in Imperata and total number of tuber-bulbs in Cyperus. In contrast. at extreme soil moisture stress, glyphosate showed reduced activity which appeared to be related to the physiological and morphological behaviour of the plants arising from the drought trealment. Application of waier to the roots of the plants grown at soil moisture stress. I week before and I week afler glypbosate spraying, enhanced glyphosate activity, probably because of the recovery of processes disturbed by ibe soil moisture deficit.     

Bioassays using detached tobacco leaves to determine the sensitivity of Peronospora tabacina to fungicides

Two bioassay methods are described which use detached tobacco leaves to measure the sensitivity of Peronospora tabacina to systemic fungicides. Tobacco leaves (13–15 cm²), treated with fungicides before or after detachment from the plant, were inoculated with sporangia in water drops and, after incubation in beakers and Petri plates, the disease severity and/or production of sporangia was determined 4–7 days after treatment with the fungicides. Of 15 systemic fungicides applied to detached leaves, eight N-phenylamides at 0.066?1.0 μg ml^?1 controlled blue mould; metalaxyl was the most effective fungicide. Isolates of P. tabacina, collected in the field from tobacco plants grown in soil treated with metalaxyl, were not resistant to the fungicide applied to detached leaves prior to inoculation. The fungicide, applied to leaves before detachment, was used to measure the efficacy of five systemic N-phenylamide fungicides sprayed on the basal and unsprayed distal portions of the leaves. Blue mould was controlled on the basal portion of the leaf by all the fungicides at 0.66?1.0 μg ml^?1, but it required the application of 3–30 times more chemical on the basal portion to achieve comparable blue mould control on the distal part of the leaf.     

Differential growth and response to atrazine between and within susceptible and resistant biotypes of Chenopodium album L.

Differential growth and response to atrazine were examined in greenhouse experiment with three populations of Chenopodium album from southwestern Ontario: two known susceptible (SI. SII) and one resistant (R). Germination of the resistant biotype was less than SII but the same as SI. R seedlings were not as mature at 16 days and weighed less at 23 days than seedlings of SI and SII. Within SI. early-(ESI) and late-flowering (LSI) variants were recognized. Older plants of R (37 and 44 days) had a greater growth rate than two of the susceptible populations (LSI and SII). In terms of vegetalive, floral, and total biomass. mature individuals of ESI were less productive than the other populations, but devoted a greater percentage of dry weight to floral production. Young plants (37 days old) were sprayed with atrazine at 00125, 0.25, 0.5, 1.25, 2.5 and 5 kg/ha. Population ESI was most sensitive to at razine; height and weight of stems and production of new leaves showed decreases at 0.25 and 0.125 kg/ha. respectively, compared to the untreated. Populations LSI and SII showed greater tolerance and decreases in these characters occurred at a higher rate of atrazine. Leaf weight per plant decreased at 0.25 kg/ha as a result of decreases in weight per unit area of leaf for all susceptible population. Growth of R as measured by the above criteria was not affected by atrazine treatments but leaf weight per unit area was slightly reduced at 2.5 and 5.0 kg/ha Single leaves of 48 day old plants were infused with at razine concentrations of 0.5, 2.0, 3.0 and 20.0 ppm. Leaf chlorosis increased with concentration and injury was greater in populations LSI and SII than in ESI. A small amount of chlorosis occurred in R.     

Spiders in sprayed and unsprayed cotton fields in Israel,their interactions with cotton pests and their importance as predators of the Egyptian cotton leaf worm,spodoptera littoralis

Densities of spiders in sprayed and unsprayed cotton fields were determined during 1981 and 1982. Eighteen families were found in an unsprayed field and 13 in sprayed fields. Species of Clubionidae, Gnaphosidae and Philodromidae comprised more than half of the total number collected. The mean weekly number of spiders per meter of cotton row was 9.1 in the unsprayed field and 5.1–5.6 in sprayed fields. Spider populations fluctuated similarly in sprayed fields in both observation years, with only one peak in July, whereas there were two peaks in the unsprayed field. Spiders played an important role in suppressing pest populations and in delaying pest outbreaks early in the cotton growing season. Thus, early pesticide applications to cotton fields are unnecessary. In a biocontrol experiment, spiders suppressed larvae of the Egyptian cotton leaf worm,Spodoptera littoralis (Boisd.), thereby reducing damage to cotton leaves.     

Epidemics of apple powdery mildew (Podosphaera leucotricha) in a mixed cultivar orchard

Epidemics of apple powdery mildew were monitored on leaves of vegetative extension shoots in a mixed-cultivar orchard in 1979. 1980 and 1981. Cultivars Cox's Orange Pippin. Golden Delicious. Ida Red and Suntan were very susceptible but little mildew developed on cv. Discovery in any year. Results with cvs Crispin and Spartan were less consistent due, in part, to differing patterns of vegetative growth. The rankings of cultivars for disease incidence (proportion of leaves with mildew), number of colonies and mildewed area were similar, and were also consistent on fungicide-sprayed and unsprayed trees in 1981. Less disease occurred on fungicide-treated Golden Delicious than on Cox's Orange Pippin. Most infections occurred on the rolled leaves at the shoot tip. Spore production was greatest on leaves at positions -1 to -4 where leaf 0 was the youngest and leaf - 1 the adjacent and older unrolled leaf.     

低钾胁迫下干旱对烤烟幼苗生理特性及钾含量的影响

为探究低钾胁迫下不同干旱程度对烤烟幼苗生理特性及烟株钾含量的影响,以烤烟品种‘K326’为试验材料,采用室内水培法,分别设置不同钾水平(低钾0.15 mmol·L^-1,常钾5.00 mmol·L^-1)和模拟干旱程度(PEG-6000浓度分别为0、5%、10%、15%、20%)双因素处理,对烟株生理指标、光合特性及烟株各部位钾含量进行测定。结果表明：相同PEG-6000浓度下,低钾水平处理的烟株地上部及根系干质量、鲜质量、根系活力、烟叶光合指标(除胞间CO₂浓度和水汽压饱和亏外)和各部位钾含量均低于常钾水平,其中低钾水平下烟株地上部及根系钾含量较常钾水平分别降低了10.62%～21.70%和35.96%～58.82%。常钾水平下,随着PEG-6000浓度的升高,烟株根系干质量、根系活力、叶片净光合速率、气孔导度、水分利用率、叶片可溶性蛋白含量、叶片POD、CAT活性均表现为先升高后降低,且均在PEG-6000浓度为10%时达到最大值,与PEG 0处理相比,各指标分别增加了16.01%、131.66%、27.87%、73.6...