Iranian Journal of Plant Physiology
Volume:4 Issue: 2, Winter 2014

The effects of 2 concentrations of kinetin, i.e., 2 and 4 mM together with 2 levels of drought stress, i.e., moderate (35% soil saturation capacity) and severe (20% soil saturation capacity) were investigated on the growth parameters of tomato including fresh and dry leaf weight, leaf number, leaf surface area, fruit number, fruit weight, and enzymatic antioxidants. To this end, first tomato plants cultivar super strain were planted in pot culture. During the early growth stage, the plants were subjected to 2 drought stress levels (35% and 20%) as well as normal irrigation (control: 50% soil saturation capacity). Also the plants were treated with foliar spraying of kinetin for 60 days. There were a total of 9 treatments in the experimental study based on a completely randomized design with 4 repetitions. The finding suggested that spraying kinetin at both levels of moderate and severe drought stress improved growth parameters in tomato. While soluble sugars increased under drought stress, the insoluble sugars content decreased. Application of kinetin on the other hand reduced soluble sugars and increased insoluble sugars content under various levels of drought stress. Finally, chlorophyll a and b contents were reduced under drought and kinetin application had no significant effect on plant pigments.

In this study the effect of four levels of nitrogen fertilizer (0, 50, 100, 150) kg/ha and four levels of super phosphate triple (0, 50, 100, 150) kg/ha were investigated on Rubia Inctorum L. (madder) under salinity stress. A factorial experiment was carried out in a research farm in Roaddasht, Isfahan based on complete randomized blocks with three replications. The results of the variance analysis showed that increase in flavonoids content (at 330 nm) was statistically meaningful under various levels of phosphorous fertilizer and interaction of phosphorous with nitrogen (P≤0.01). Flavonoid content was also significantly increased under various levels of nitrogen (P≤0.05). Moreover, the amount of proline in the leaves of madder showed significant variation under different levels of phosphorous, nitrogen, and the interaction of nitrogen and phosphorous at P≤0.01. Also the performance of shoots was significantly affected by different levels of phosphorous and its interaction with nitrogen at P≤0.01. Flavonoids contents at 330 nmwavelength varied between 0.78 to 0.411 nanometer and while the maximum of this flavonoid level was observed under the phosphorous, the minimum was related to 150kg/ha of phosphate and the control (0 kg/ha nitrogen). This suggests that by increase in phosphorous and decrease in nitrogen fertilizers, phenolic compounds are reduced in the plants. The maximum and minimum proline contents were observed under 150 kg/ha nitrogen and phosphorous treatment and control, respectively. The performance of shoots varied ranging from 1.75 to 0.75 kg/m2. Maximum performance was recorded under 150 kg/ha nitrogen and phosphorous treatment and the decrease in phosphorous negatively affected plant performance. The results therefore suggest that yield and secondary metabolites increased with an increase in nitrogen and phosphorous treatment in the salt stressed madder.

The present work aimed at investigating changes in growth and some metabolic activities in NaCl-stressed bean plants, and assessing the role of ascorbic acid to alleviate these changes. The field experiment was carried out to study the response of presoaked fava bean seeds (Vicia fava cv. Misr 2) in freshly prepared ascorbic acid (50 ppm ≈ 0.3 mM; as recommended dose as described by El-Tayeb, 1995) or distilled water (control) for 4 hrs at natural environmental conditions, to salinity stress during different growth periods. At vegetative stage, the fresh and dry weights were decreased with salt treatment. The shoot length was hardly, if at all, affected by salinity stress either in the plants treated with ascorbic acid or not. The pigment biosynthesis was substantially affected by salt treatment. Addition of ascorbic acid to stressed plants reduced the inhibitory effect of NaCl on pigment content. Salinity enhanced the accumulation of reducing sugars in both root and shoot of Vicia fava, particularly at the high level of NaCl during the vegetative stage of growth. Whereas, the salt stress caused a decrease in the sugars content of both plant organs during the flowering and fruiting stages. NaCl treatment caused a reduction in sucrose content of Vicia fava root at the high level of NaCl during vegetative stage. In addition, the polysaccharide content of roots and shoots gradually increased with the progress of age, except at fruiting stage. These findings suggest that ascorbic acid achieved better results during growth stages.

Acetyl coenzyme A is an important molecule in metabolism playing role in many biochemical reactions. Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production. In order to find out if this chemical compound could affect physiological and morphological characteristics of rosemary plant, the present study was carried out in a factorial design including two factors (acetyl-co A and the time of treatment application) based on the completely randomized block design. Acetyl-coA was used in 6 different concentrations (0, 25, 50, 100, 200, and 400 mM) which were applied to plants 1, 2, and 3 times witha seven - day interval. The application of acetyl-coA 200 mM, had significantly improved the factors such as dry weight of leaves, chlorophyll a, and the activity of antioxidant enzymes catalase and glutathione peroxidase.

In this study, the role of salicylic acid pre-treatment (0.01, 0.1 mM was investigated) in inducing salt tolerance in sweet basil. Results showed germination percentage, length of shoot and root, fresh and dry weight of leaf, and photosynthetic pigments were decreased in response to high salinity but the lipid peroxidation, coefficient allometry, and soluble sugars increased. In plants pre-treated with salicylic acid (especially 0.01 mM) the adverse effects of salinity on all measured parameter were alleviated.

Salinity is a main and common stress which decreases the amount of agriculture products and natural plants in many areas of the world. In this study, the effect of salt stress on three varieties of Lotus corniculatus 'Karaj', 'Jolfa', and 'Ardabil' was investigated. Plants were cultured in hydroponic condition with four NaCl treatments (0, 50, 100, 150 mM). The amounts of proline, glycine betaine, soluble sugars as well as Na+ and Cl- were analyzed. The results showed that sodium and chloride content in all varieties significantly increased in shoot (p<0.05). The amounts of proline and soluble sugars significantly increased in all varieties (p<0.05). However, increasing in NaCl concentration raised significantly glycine betaine content in leaves of the varieties (p<0.05). As far as the measured factors are concerned, it seems that 'Jolfa' and 'Karaj' have a higher capacity to tolerate salt stress particularly in 100-150 mM NaCl compared with 'Ardabil'.

The present study was conducted to induce callus from different in vitro grown seedling explants of shoot, root and leaf segments in order to develop shoot buds and rooting from callus. The sterilized seeds were cultured on Murashige and Skoog medium, and then the explants were cultured from seedling and transferred to an MS medium supplemented with different concentrations of BAP, kinetin, NAA, and 2, 4-D growth regulator hormones. Among all explants, the leaf explants should produce significant callus induction (97.79 %) on MS + 1.0 mgl-1 BAP medium. After 4 weeks, the obtained calluses were transferred to a new regeneration media with different concentrations of BAP and NAA and then the calluses were sub cultured on the same medium every 2 weeks. Overall, the maximum regeneration frequency was obtained from MS medium containing 0.1 mgl-1 NAA and 1.0 mgl-1 BAP.

Arginine (Arg) is reported to contribute in reduction of destructive effects of biotic and abiotic stresses through three pathways and their end products (proline, polyamine and nitric oxide). Two isomers of arginine (L and D) have been applied as pre-treatment and then tomato plants were subjected to drought stress. The effects of these isomers on some physiological parameters and expression of arginase 1 (ARG I) (one of the enzymes in proline biosynthesis) pathway have been investigated. The results showed that leaf relative water content (RWC) of tomato plants under drought stress decreased and pre-treatment with L-Arg improved RWC, but D-Arg did not. Drought stress caused a significant decrease in photosynthetic pigments but arginine had no effect on these parameters. Sugar content and lipid peroxidation level increased under stress. However, arginine treatment caused decrease in lipid peroxidation while it did not change sugar content significantly. Proline also significantly increased under drought stress and L-Arg many time increased it content. Increment in expression of arginase1 may be the cause for this increment. On the other hand, the expression of arginase1 and proline content with D-Arg was less obvious. The results of the present study indicate that in tomato plant in addition of L-Arg, arginase can use D-Arg substrate to produce proline. However D-Arg has been reported as an analog of L-Arg which could block ADC pathway. Our molecular and biochemical results showed that this enantiomer could not inhibit arginase pathway.