Freezing damage is a major limiting factor to Pistachio cultivation in cold climates. Assessment of pistachio genotypes to freezing stress is important for the selection of tolerance cultivars in these regions. In this study, nine genotypes belong to six Pistacia species (P. terebinthus L., P. atlantica Desf., P. atlantica subsp. kurdica P. atlantica subsp. mutica, P. khinjuk Stocks., P. vera var. Sarakhs, P. vera cv. Badami-Riz-Zarand I, P. vera cv. Badami-Riz-Zarand II) and an interspecies hybrid named UCB1 (P. atlantica × P. integrrima) were evaluated to freezing stress at temperatures of −4, −8, −12 and, −16°C in the months of December, January and February. Results showed that electrolyte leakage (EL) percentage and means of eco-physiological parameters varied among genotypes with the highest soluble carbohydrates and phenolic compounds observed in species of P. atlantica subsp. kurdica and P. vera var. Sarakhs respectively. In February, the highest calcium and potassium concentrations of shoot were observed in P. terebinths and P. vera var. Sarakhs genotypes respectively. The highest EL percentage was observed at −16°C in P. atlantica and P. khinjuk and the lowest in P. terebinthus and P. vera var. Sarakhs.

Cotton fibre yield and quality are markedly influenced by drought and high-temperature stress. We examined the traits of the leaf stomata in 39 cotton genotypes subjected to exogenous phytohormone abscisic acid (ABA) signalling, electrolyte leakage under 40°C thermal stress, and relative GhHsfA, GhbZIP and GhHSP70 expression levels under two treatments. Stomatal density and area ranged from 66 to 182/mm2 and 663 to 1305 μm2, respectively. Under exogenous ABA signalling, the changes in stomatal aperture (ΔSAp) were in the range of 2.5–31.2%; ΔSAp and relative GhHsfA, GhbZIP and GhHSP70 expression levels were significantly correlated, respectively. Electrolyte leakage increased unequally among cotton genotypes after heat stress. The changes in electrolyte leakage (ΔEL) and relative GhHsfA, GhbZIP and GhHSP70 expression levels were very strongly correlated, respectively. Their relative expression levels could be used as references for the rapid identification of stress-tolerant cotton strains. Cluster analysis of the 39 cotton genotypes indicated that Xinluzao36, Shiyang1, shinong98-7 and Zhongmiansuo293 are heat- and drought-resistant. We integrated both analysis of physiological parameters and molecular methods to identify cotton varieties with the drought and heat tolerance, in order to provide a reference for the selection of materials and methods for the research and production of cotton.

Rapid, non-destructive methods for measuring seed germination and vigour are valuable. Standard germination and seed vigour were determined using 81 soybean seed lots. From these data, seed lots were separated into high and low germinating seed lots as well as high, medium and low vigour seed lots. Near-infrared spectra (950–1650 nm) were collected for training and validation samples for each seed category and used to create partial least squares (PLS) prediction models. For both germination and vigour, qualitative models provided better discrimination of high and low performing seed lots compared with quantitative models. The qualitative germination prediction models correctly identified low and high germination seed lots with an accuracy between 85.7 and 89.7%. For seed vigour, qualitative predictions for the 3-category (low, medium and high vigour) models could not adequately separate high and medium vigour seeds. However, the 2-category (low, medium plus high vigour) prediction models could correctly identify low vigour seed lots between 80 and 100% and the medium plus high vigour seed lots between 96.3 and 96.6%. To our knowledge, the current study is the first to provide near-infrared spectroscopy (NIRS)-based predictive models using agronomically meaningful cut-offs for standard germination and vigour on a commercial scale using over 80 seed lots.

The mode of action of quinclorac was investigated in broadleaf and grass species. Quinclorac induced characteristic auxinlike symptoms in broadleaf species but not in susceptible grasses. In susceptible grasses, quinclorac caused necrotic bands near the zones of elongation in shoots and roots. Electrolyte leakage was induced by quinclorac in smooth crabgrass and other susceptible grasses but not in tolerant grass or susceptible broadleaf species. In smooth crabgrass, increased electrolyte leakage and reduced fresh weight were rate dependent, and initially specific to young tissues. An inhibitory effect on elongation in the youngest leaf of smooth crabgrass and in primary roots of corn was detected 6 and 3 h after quinclorac treatment, respectively. Electrolyte leakage required more than 12 and 6 h in the leaf and root, respectively. Depolarization of corn root cell membrane potential was not observed in a 6-h treatment period. Results presented here provide additional evidence that quinclorac activity differs between susceptible broadleaf and grass species. In addition, the action of quinclorac appears to be similar in both shoot and root tissues of susceptible grasses. It is proposed that quinclorac-induced electrolyte leakage in susceptible grasses is a secondary response and that the primary mechanism of action involves inhibition of an as yet unknown metabolic process associated with cell expansion.

Effects of difenzoquat on wild oats grown under controlled environmental conditions were studied. Seedling height and fresh weight were significantly reduced 5 days after postemergence treatment. Dose-dependent increase in cell membrane permeability was detected after a 12-h exposure to the herbicide. Scanning electron micrographs showed normal leaf hairs and cuticular wax but swollen guard cells 10 days after treatment. Ultrastructural changes occurred before the visible symptoms. The primary effect of difenzoquat appears to be the disruption of the tonoplast and plasmalemma. The tonoplast showed greater damage than the plasmalemma. Secondary effects included damage to mitochondria and chloroplasts. Mitochondria were swollen and often ruptured, but the effect did not increase with the duration of exposure. Chloroplasts became spherical in shape, and their contents were also affected. The changes included: accumulation and then disappearance of starch granules, swelling of frets, fusion of granal thylakoids, detachment and then rupture of the outer membrane of the envelope, and clumping of ribosomes. By contrast, natural senescence caused greater injury of the plasmalemma than the tonoplast, a marked increase in size of plastoglobuli, and loss of starch grains without early accumulation.

Field and laboratory experiments were conducted to evaluate the effect of glyphosate concentration, surfactant concentration, and ammonium sulfate on the control of giant burreed when applied through a ropewick applicator. Under non-flooded conditions, a 30% (v/v) solution of glyphosate applied with a ropewick applicator gave the highest giant burreed injury in 1987 and 1988, and reduced corm and rhizome viability compared to the nontreated control in 1987. Warm, dry conditions may have been responsible for poor long-term control in 1988 by reducing translocation of glyphosate to rhizomes. Addition of ammonium sulfate or surfactant did not influence glyphosate toxicity to giant burreed when applied with a ropewick applicator. In the laboratory, leaf necrosis at the point of application was observed with surfactant at 0.6% or 1.2% regardless of glyphosate concentration. Absorption of 14C-glyphosate increased two-fold with the addition of surfactant, and translocation to roots and rhizomes decreased almost two-fold as surfactant concentration was increased from 0 to 1.2%. Electrolyte leakage increased with 30% glyphosate when surfactant concentration was increased from 0 to 1.2%. Localized leaf necrosis and disruption of tissues inside the leaf may be responsible for reduced giant burreed control with glyphosate and surfactant applied in high concentrations.

Protoporphyrinogen oxidase (protox)-inhibiting herbicides damage cell membranes, resulting in electrolyte leakage. A whole-plant dose-response study and a rapid assay that measured electrolyte leakage was used to determine the response of wild mustard, soybean, and protox inhibitor–susceptible and protox inhibitor–resistant common waterhemp to increasing doses of three protox inhibitors: acifluorfen, fomesafen, and sulfentrazone. For the dose-response study, whole plants were treated with the three protox-inhibitor herbicides. Electroconductivity assay 1 consisted of cutting discs from leaf tissue and submerging them in an incubation medium containing concentrations of acifluorfen, fomesafen, or sulfentrazone. In electroconductivity assay 2, the entire leaf was treated with solutions containing acifluorfen, fomesafen, or sulfentrazone. The whole-plant dose-response study showed increasing visible injury with increasing herbicide rates for all species and all herbicides. The order of visible injury was wild mustard > susceptible common waterhemp > resistant common waterhemp > soybean. In assay 1, electrolyte leakage from leaf discs treated with acifluorfen or fomesafen increased with increasing herbicide concentrations, and was similar for all species. In contrast, electrolyte leakage from leaf discs treated with sulfentrazone did not increase with increasing herbicide concentrations for any species. In assay 2, only wild mustard leaf discs increased in electrolyte leakage with increasing herbicide rates of acifluorfen, fomesafen, and sulfentrazone and followed the regression curves established by the whole-plant dose-response study. However, assay 2 was not able to distinguish between susceptible wild mustard and tolerant soybean, or between susceptible and resistant waterhemp.

Genetic diversity identified in the Capsicum genepool has been utilized extensively to improve pepper disease resistance, fruit quality and varied yield attributes. Little attention has been dedicated to evaluating the breadth of potential diversity within Capsicum for fresh-cut attributes and genetic enhancement of fresh-cut fruit quality. We evaluated fresh-cut attributes in pepper accessions with diverse fruit phenotype selected from available cultivars and the USDA, ARS Capsicum genebank. Subjective assessment of product quality and objective measurement of package atmospheric composition, tissue juice leakage and membrane electrolyte leakage after 7, 10 and 14 d of storage identified significant differences for fresh-cut attributes among as well as within sweet bell, large elongate, jalapeno and serrano germplasm. Sweet bell and large elongate fruited accessions generally exhibited increasing electrolyte leakage over days of storage, whereas jalapeno and serrano accessions maintained stable electrolyte leakage levels. Jalapeno and serrano fruit classes were typified by faster decline in package headspace O2 and accumulation in CO2 partial pressures in comparison to sweet bell and large elongated fruit classes. Regression analysis demonstrated a relationship between overall visual quality and electrolyte leakage after 14 d of storage for sweet bell and large elongated fruit classes. The results demonstrate extensive variation in Capsicum germplasm to improve pepper for fresh-cut applications and facilitate research to better understand physiological and heritable determinants of fresh-cut product quality.

Cultivated orchids are the most abundantly attacked by polyphagous mealybugs. This study documented how different density of mealybug Pseudococcus longispinus (Targioni Tozzetti) infestation is associated with a response of antioxidative systems of Phalaenopsis × hybridum ‘Innocence’. The degree of cell damage, estimated by electrolyte leakage measurement and the level of thiobarbituric acid reactive substances (TBARS), the content of pigments as well as the activity of antioxidative enzymes and proline level, as measurements of stress and stress compensation in moth orchid were examined. The highest electrolyte leakage (EL) value among samples from colonized plants was found in the orchids from series III (50 individuals/plant), whereas the lowest in the plants from series II (20 individuals/plant). The TBARS content reached the highest level at the lowest number of feeding insects (series I). Peroxidase activity toward guaiacol was significantly increased in series I (5 individuals/plant). The highest catalase activity was recorded in plants colonized by the highest number of scale insects (series III). Whereas, the highest value of proline was in series II. The content of individual photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) in plant tissues did not vary significantly between control and colonized orchids. The results have not confirmed hypothesis that the increasing number of mealybugs occurring on plant enhanced plant physiological response. The degree of longtailed mealybug infestation on plants was positively correlated only with electrolyte leakage and catalase activity in leaf tissues.

Antioxidants protect seeds from oxidative damage during storage, supporting the maintenance of seed viability and the ability to germinate post-storage. No data on antioxidants during long-term storage are available for the seeds of the halophyte Suaeda maritima. Therefore, changes in lipid-soluble antioxidants in the tocopherol family (α-, γ-, δ-tocopherol), were investigated in seeds stored for up to 16 years at 4°C at a seed moisture content of 10–13%, as well as changes in the water-soluble antioxidant glutathione (GSH) and electrolyte leakage. Seed oil content was also measured and determined to be 22%. During the first 3 years of storage, seed viability remained high and the concentration of total tocopherol was stable. Thereafter, both seed viability and α-tocopherol concentration rapidly decreased and electrolyte leakage increased, while γ-tocopherol and δ-tocopherol concentrations did not correlate with seed viability. Although the concentrations of neither GSH nor glutathione disulphide (GSSG) alone were correlated with seed viability, the glutathione half-cell reduction potential (EGSSG/2GSH) was strongly correlated with viability throughout storage and increased before the onset of viability loss. Hence, in this species EGSSG/2GSH appeared to be an ‘early warning’ system preceding viability loss while α-tocopherol concentration changed concomitantly with viability.

Sunflower (Helianthus annuus L.) seeds show more germination at high temperatures (25–30°C) than at temperatures below 20°C. Osmopriming with polyethylene glycol-6000 for 3–5 days at 15°C strongly increases germination at suboptimal temperatures. This stimulatory effect of priming persists after seed redrying and during subsequent storage at 20°C (55% RH) for at least 14 weeks. However, primed seeds deteriorate faster than untreated seeds during accelerated aging (45°C, 100% RH). The longer the priming treatment, the higher is the amount of germination but at the same time the higher is the sensitivity of seeds to accelerated aging. Priming enhances the respiratory activity of seeds transferred onto water and their ability to convert 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene. These effects remain after drying the seeds and are maintained in part during dry storage, whereas they disappear during accelerated aging. These results suggest that ACC-dependent ethylene production might be a good indicator of seed vigour; it increases with duration of priming and decreases very early during aging, well before significant loss of seed viability. Decrease in ACC conversion to ethylene indicates that aging is probably associated with membrane deterioration since in vivo ACC oxidase activity depends on membrane properties. However, no increase in electrolyte leakage is observed during aging.

In this paper, the response to temperature of three physiological processes has been examined in detail in seedlings of sorghum and pearl millet. These have been compared with their field performance under high temperature conditions with the aim of developing laboratory-based screening techniques for seedling thermotolerance. Membrane thermostability, as assessed by electrolyte leakage, seedling re-growth and protein synthetic ability were measured in seedlings exposed to a range of temperatures using a thermal gradient bar. The effect of genotype, seedling age and pre-treatment was examined. Differences between genotypes were only apparent after seedlings had been given a brief high temperature pre-treatment (2 h at 43°C). Similar results were found with all three methods used and their suitability for use in the screening of large numbers of entries is discussed. Significant correlation was found between the ability of membrane thermostability to acclimate and seedling survival in the field.