فیزیولوژی گیاهان
سال:1392 | دوره: | شماره: |تعداد مقالات:8

The effect of different thiourea (TU) concentrations (10 and 20 mM) on antioxidants, protease activity and protein content with and without H2O2 (50 mM) induced stress was investigated in wheat leaves. A gradual decrease in protein content with a peak at 72 hours was observed in stressed as well as control leaves. This gradual decrease in leaf protein content at different time intervals was completely prevented by 20 mM TU treatment. Leaf protease activity was increased due to oxidative stress by H2O2 while it decreased after 20 mM TU treatment under stressed and non-stressed condition. In general, catalase (CAT) activity increased under oxidative stress and after both thiourea treatments. However, at 72 hours, CAT activity reduced along with simultaneous increase in peroxidase activity under H2O2 induced stress. Actually, stress induced reduction in CAT activity at 72 hours was compensated with peroxidase. Oxidative stress and TU treatments generally raised the peroxidase activity. TU treatment followed by oxidative stress condition also increased the leaf peroxidase activity irrespective of applied concentration. Again, H2O2 and TU treatment induced reduction in CAT activity at 96 hours was compensated with a prompt increase in peroxidase activity. Collectively, H2O2 treatment increased the antioxidant and protease activities. Moreover, thiourea treatments prevented the protein loss (20mM TU), decreased the protease activity and enhanced the CAT and peroxidase activities which resulted in protective effects. Dose dependent effects of TU treatments were observed mostly.

Freshly harvested tomato fruit (Solanum lycopersicum) were pre-treated with 0, 50, and 100 mM prohexadione-calcium (Pro-Ca) and then stored at 1oC for 21 days to investigate the effect of Pro-Ca treatment on electrolyte leakage (EL), malondialdehyde (MDA), proline and total phenols contents, and activity of phenylalanine ammonia-lyase (PAL) in relation to chilling injury (CI). Treatment with Pro-Ca, without significant difference between two applied concentrations, mitigated chilling injury, reduced EL and MDA content and increased proline content. Also, our results indicated that during storage time fruits treated with Pro-Ca exhibited significantly higher PAL activity, but total phenols content was not significantly affected by Pro-Ca treatments. These results suggested that Pro-Ca protects tomato fruit from CI by activation of PAL enzyme, enhancing proline contents and reducing MDA content, and thus maintaining membrane integrity.

Critical growth stage of cotton crop was investigated by artificially imposing water stress under field conditions. The crop was given water deficit stress for a period of 30 days at squaring (SS) and first boll split (BS) phases by maintaining the leaf water potential (yw) at –2.2+0.2 MPa whereas in control plots yw was maintained at -1.6+0.2 MPa by irrigation scheduling. The average irrigation water applied during two years was 2432 m3, 2174 m3, and 2194 m3 in NS, SS, and BS treatments, respectively. The results revealed that the imposed water stress, at either stage of crop, had adverse effects on cotton crop performance. The main stem height decreased by 12% and 7.4%, inter-nodal length by 9.2% and 4.3% in SS and BS, respectively over NS treatment. The decrease in dry biomass production was 4% and 7% in leaf; 21% and 11% in stalk and 20% and 13% in fruit in SS and BS treatments, respectively. Gas exchange characteristics were also adversely affected by imposed water stress showing a decrease of 18% and 28% in stomatal conductance, 16% and 22% in transpiration rate and 24% and 30% in net photosynthetic rate in SS and BS treatments, respectively. The decrease in seed cotton yield was 9.5% and 2.8% in SS and BS treatments, respectively. Chlorophyll (SPAD values), electrolyte leakage and cell injury values increased over non stressed crop. Lint percentage and fibre strength increased whereas fibre length decreased significantly in BS treatment. It was concluded that the squaring phase is more critical to water deficit stress in cotton.

Callus cultures were established in vitro from leaf explants of Malva neglecta and were sub-cultured several times until a rapid-growing cell line was obtained. The calluses were exposed to different doses of ultraviolet (UV) radiation as follows: 0, 432, 864, and 1296 J/m2 for UV B and 0, 612, 1284, and 1836 J/m2 for UV C, corresponding to 0, 30, 60, and 90 min radiations, in tandem. Exposure to UV, in particular for longer periods, reduced the viability and membrane integrity of Malva cells. This however, increased total contents of flavonoids, anthocyanins, and wall-bound phenolic acids. Among different pharmaceutical compounds of Malva cells increase of malvidin, catchin, cinnamic acid, and tannic acid was remarkable in UV-treated cells, compared to those of the control cells. According to the results, treatment of Malva cells with UV provides an attractive alternative to whole plants for effective production of specific phenolic compounds.

Ascorbate is a strong antioxidant which has remarkable biological effects on plants growth, including an improvement in plants' tolerance under salinity stress conditions. In the present study, the effect of salinity stress and its interaction with ascorbic acid was investigated on some morphological traits, cell membrane stability, leaf relative water content, and extract yield of purslane (Portulaca oleracea L.) under greenhouse conditions. This research was down as factorial based on completely randomized design with 4 replications. The plants were treated in different concentrations of sodium chloride (0, 70, 140, and 210 mM) and ascorbic acid (0, 10, and 20 mM) for 4 weeks after germination. In the treated plants with salt, increases in sodium chloride concentration reduced growth parameters such as roots and shoots fresh and dry weights, roots and shoots lengths, extract yield and relative water content (RWC). However, cell membrane stability and extract percent increased. Under the same salt stress conditions, increase in ascorbic acid concentrations improved all the studied characters, so that spraying 20 mM ascorbate conducted to the maximum amount of extract percentage (0.0054 %) and extract yield reduced (0.037 g/plant). The study also revealed that purslane is a medicinal plant with a high resistance to salinity stress and can generally be cultivated in saline soils.

Greenhouse experiments in a completely randomized design were carried out to investigate the effects of nitroxin fertilizer (0, 1 and 2 li/ha) on morphological and physiological traits of Amaranthus retroflexus in 2013. The traits in the study included plant height, fresh and dry weight of shoots, roots, stem and leaf, Chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, anthocyanin, and flavonoids. Findings showed that nitroxin biofertilizer had linear and nonlinear regression effect on the fresh and dry weights of shoot. Increase in nitroxin also increased fresh and dry weights of leaf, stem, chlorophylls a, b, total Carotenoids and anthocyanin as well as carotenoids content of the plants linearly. The results showed that the correlation between the traits there is a significant relationship. Also fresh weights shoot with each of traits dry weights shoot, fresh and dry weights of leaf, fresh and dry weights of stem and dry weights of shoot with each of traits fresh and dry weights of leaf, fresh and dry weights of stem and fresh weights of leaf with each of traits fresh and dry weights of stem, dry weights of leaf and dry weights of stem with each of traits dry weights of leaf and stem there is a significant relationship. Chlorophyll a with chlorophyll b, total, carotenoids and flavonoids and chlorophyll b whit chlorophyll total, carotenoids and flavonoids and chlorophyll total whit carotenoids and flavonoids and carotenoids with flavonoids there is a significant relationship. The results of step-wise regression analysis showed that dry weight of stem, had positive and fresh weight of shoots reduced effect on dry weight of shoots.

An understanding of biochemical events of cold storage may lead to more effective methods of preventing apple fruits from ripening and keeping their quality. This study aimed at determining the level of reduced and oxidized forms of ascorbic acid, and the activity of ascorbate peroxidase, catalase, and superoxide dismutase enzymes changes in pulp of Golden delicious apple cultivar during cold storage. Apples were kept in common cold storage condition (1oC, 95% - 97% RH) for 135 days for subsequent analysis. During cold storage condition, no significant changes were observed in the content of reduced and oxidized forms of ascorbic acid. However, levels of total flavonoids declined as storage time progressed. Superoxide dismutase and ascorbate peroxidase activities were decreased while the activity of catalase was increased.

In order to investigate the influence of sulfur coated seeds in SCS (a moisture absorbent polymer layer on seeds) on physiological traits of cotton, a field experiment was conducted in completely randomized design with factorial arrangement with 3 replications. Three planting date included early (E), optimum (O), and delayed (D) planting time. Seed coating priming treatments consisted of F (fuzzy seeds, control), FS (fuzzy seeds with SCS), FSS (fuzzy seeds with sulfur coating and SCS), D (delinted seeds), DS (delinted seeds with SCS), DSS (delinted seeds with sulfur coating and SCS). Findings showed that the effects of planting date and seed coating treatments on chlorophyll, anthocyanin, proline, and glycine betaine content were significant. Interaction of treatments of seed coating and planting date treatments showed that treatments of seeds with ED, EDS, ODS and DDSS, had the highest content of chlorophyll. EFSS treated seedlings had the highest content of anthocyanin (0.58 mg g-1Fw) which increased with treatments application while anthocyanin content decreased in EDS and EDSS treatments, in comparison with ED. The highest (0.76 mg g-1Fw) and lowest (0.21 mg g-1Fw) concentrations of anthocyanins were recorded when F seeds were planted at optimum date (OF) and delayed (DF) planting dates, respectively. In three planting date treatments of ED (8.82 mg g-1Fw), OFS (8.83 mg g-1Fw), and DDS (9.37 mg g-1Fw), the highest proline content was obtained. In early planting treatments, glycine betaine content decreased in all coating treatments. ED and EDS treatments had lowest glycine betaine content. Treatments of seed coating in optimum and delayed dates of planting resulted in identical amounts of glycine betaine production.