JOURNAL OF PLANT PHYSIOLOGY AND BREEDING
Year:2016 | Volume:6 | Issue:2 |Papers Count:6

The leaf growth and cross-sectional area of durum wheat during its development may be reduced under salt stress due to vascular architecture alterations of leaves. A hydroponic experiment was conducted to compare growth rate and vascular architecture changes of two durum wheat cultivars including Shabrang and Yavaroos under 0 and 100 mM NaCl. Plants were sampled at the three-leaf stage growth. Results showed that under salt stress at 15 DAG, Shabrang with 0.69 mm/h had a greater elongation rate than Yavaroos (0.27 mm/hr). Likewise, under salt stress at 25 mm above the leaf base, 32 and 37% reductions in cross sectional area were observed in Shabrang and Yavaroos, respectively. In all treatments, maximum leaf width was obtained at the growth zone (25 mm above the leaf base). In both cultivars, the leaf cross-section of the control consisted of one midrib, 5 large veins and 11-21 small veins, while it composed of one midrib, 4 large veins and 3-12 small veins under salt stress. Overall, in both cultivars, comparison of control and salt stress treatments showed that the reduction in protoxylem area at 5 mm was greater than 100 mm above the leaf base. It can be concluded that the reduction in the cross-section of durum wheat is mainly correlated with a decreased number of small veins, and Shabrang cultivar with greater number and area of small veins along the leaf base had higher leaf growth and expansion rate than Yavaroos, when plants exposed to salt stress. This probably can explain why Shabrang cultivar might be more tolerant to salt stress than Yavaroos.

To optimize conditions for micropropagating Galanthus transcaucasicus Fomin, the effect of explant type, different concentrations of sucrose, type and different concentrations of auxin were examined on bulblet production. For the induction of bulblets, three types of bulb scales were usesd as explants. A two-step sterilization procedure was applied. Assessments were made after incubation for 20 weeks at 23±1ºC with 16h photoperiods. Highest number of bulblets were proliferated culturing bulb scales on modified MS medium supplemented with 2.0 mg.l-1 BA and 2.0 mg.l-1 IBA. About 27% of bulblets were bigger than 5 mm in diameter, suitable for acclimatization. With the increase of sucrose concentration, number of bulblets decreased, but their size increased. This protocol provided a basis for future study on large-scale multiplication system for commercial nurseries of Galanthus transcaucasicus.

For centuries, Damask rose has been one of the most popular species of the rose family. Damask rose can be propagated using vegetative methods such as micropropagation. In this research, the use of temporary immersion system was reported for the first time for Damask rose micropropagation. For this reason, a traditional temporary immersion system was designed to facilitate its micropropagation. To optimize this system, the effects of the BAP concentration, immersion time, explant size, number of explants per temporary immersion unit were investigated in the independent experiments using completely randomized design. Temporary immersion system was also compared with the solid and liquid media. The highest shoot number per explant was obtained from a temporary immersion system using an immersion time of 3 min every 150 min (11.8 shoots), a modified MS medium with 6 mg l-1 BAP (12.33 shoots) and explants with shoot length of 4 cm (12.45 shoots). Results indicated that the temporary immersion system was significantly better than solid and liquid media for the shoot number per explant (10.66, 2.56 and 5.66, respectively).

Environmental stresses are the most important factors that reduce plant growth in stages of development. The presence of aluminum in acidic soils as an environmental stress has an impact on different parts of the plant and reduces root growth, water absorption and nutrients and increases susceptibility to drought. In order to evaluate the effect of aluminum stress levels on wheat at germination stage, an experiment was conducted as factorial based on completely randomized design with three replications. The root and shoot characters of four wheat cultivars (Arta, Gascozen, Moghan3, Mihan) at seedling stage were studied at eight stress levels (control, 0.5, 1, 1.5, 2, 2.5, 5 and 10 mM Al3+). The root and shoot fresh weight, root and shoot length, root volume and area, root number and Root/Shoot ratio were measured. Results showed that stress level had significant effects on all studied traits. Also, wheat cultivars were significantly different for number, volume, weight and area of root and also shoot length. Interaction between cultivars and stress levels was significant for root number. The Mogha3 variety had higher root number at 2.5 mM Al3+ stress level. In all of varieties, the root number increased by increasing of Al3+concentration. Comparison of means showed that Al3+stress caused significant reduction in all studied traits except root number. The Moghan3 variety had higher means for studied traits as compare with other varieties.

Recent studies have introduced seed priming with H2O2 as an effective technique to alleviate abiotic stresses in plants. In the current study, accomplished at Faculty of Sciences, Shahrekord University, seeds of medicinal plant Artemisia aucheri were primed with H2O2 (0, 10, 50, 90 and 140 mM) and grown under salt stress (0 and 150 mM NaCl) for one month. Results showed a decrease in H2O2 and malonyldialdehyde concentrations by H2O2 priming leading to diminish lipid peroxidation at the cellular level. Moreover, seed priming with H2O2 (particularly at 90 mM) increased biomass, total water content, chlorophyll (a+b) and carotenoids concentrations, total phenolic content and antioxidant capacity in the plants from primed seeds under both normal and saline conditions. Higher activities of superoxide dismutase and catalase were observed in the primed A. aucheri with 90 mM H2O2, while the activity of ascorbate peroxidase was at the maximum level at 140 mM H2O2 priming condition. Additionally, hydroxyl and super oxide radicals scavenging activities were at the maximum level in the plants from primed seeds with 90 mM H2O2. Data revealed that H2O2 priming can induce salt tolerance in A. aucheri plants by adjusting physiological and metabolic processes such as photosynthesis, ROS scavenging and detoxification and brings about an improved growth and development in this species. Furthermore, H2O2 priming at 90 mM augmented antioxidant activity and reducing power in A. aucheri suggesting an increase in its medicinal properties.

Phytohormones such as auxin are known to be involved in alleviating the detrimental effects of salinity by modulating the activity of enzymatic antioxidants and improving antioxidant system, which help in sustaining plant growth. The present study envisaged revealing the role of exogenous application of indole-3-acetic acid (IAA) in improving defense mechanisms in two genotypes (FL485 and IR29, salt tolerant and salt susceptible, respectively) of rice against NaCl stress. The results showed that salt stress led to an increase in the ascorbic acid (AsA) content of the tolerant cultivar suggesting that oxidative defense system was very operative in this cultivar. Exogenous application of IAA further increased the activities of AsA and ascorbate oxidase in the salt stressed FL485, whereas such effect was not observed in the susceptible cultivar (IR29). IAA was found to be more effective in enhancing the activities of a-tocopherol in salt stressed rice plants with more efficiently in the salt tolerant cultivar. In addition, IAA markedly increased hydrogen peroxide (H2O2) concentration in both cultivars as compared to untreated plants. Lipid peroxidation levels of both cultivars under salt treatment showed no change with foliar applications of IAA.