JOURNAL OF PLANT PHYSIOLOGY AND BREEDING
Year:2016 | Volume:6 | Issue:1 |Papers Count:6

The importance of different species of savory is due to having phenolic compounds such as carvacrol and thymol in the essential oil and rosmarinic acid in the extract, having strong antioxidant and antimicrobial effects. This study was conducted on five ecotypes of Satureja rechingeri in in vitro and in vivo experiments. After determining the best shooting and rooting medium, micropropagation was done and clones were prepared. Water stress treatments were prepared by increasing agar up to 100% followed by selecting the most tolerant and sensitive clones. In the in vivo experiment, effect of water stress was studied in a greenhouse with irrigation withhold and sampling at five stages. Ten morphological and physiological characters were recorded from both experiments. The tolerant clone had superior tolerance to water deficit. Increasing the agar concentration up to 66% had no effects on rooting and the growth rates of shoots but more increase led to a sharp reduction in the growth rate and root differentiation. In the greenhouse, the tolerant clone was tolerated the stress up to nine days without showing any symptoms, but the continuation of stress led to a sharp increase in proline and soluble sugars and the reduction of plant pigments and leaf osmotic potential. This research was a kind of drought simulation at in vitro condition, performed for the first time for identification and screening of drought tolerant clones of savory.

Assessing the tolerance of medicinal plants is important for planting them in drought areas. Arginine is a growth regulator and its role in plants’ tolerance to environmental stresses such as drought has been investigated. To evaluate the protective effects of arginine against osmotic stress induced by polyethylene glycol in ajwain (Trachyspermum ammi) seedlings, an experiment was conducted as a completely randomized design in a factorial arrangement with three replicates. Experimental treatments included arginine at three levels (0, 10 and 20 mM) and osmotic stress (induced by polyethylene glycol 6000) at three levels (0, 13.5% and 17% (W/V)). Results showed that arginine application through the root medium caused the reduction of H2O2 content, lipid peroxidation (malondialdehyde and other aldehydes) and lipoxygenases activity and increased the antioxidant enzymes activity (calatase, ascorbate peroxidase and guaiacol peroxidase), protein content and proline content under osmotic stress. Therefore, it seems that the application of arginine greatly improves the dehydration tolerance through elevated activities of antioxidant enzymes.

The aim of present study was to evaluate the effects of drought stress on net photosynthesis rate (Pn), stomatal resistance, water use efficiency (WUE) and biomass (BM) of six maize (Zea mays L.) hybrids. Drought stress applied by withholding water supply at 4-5 leaf stage (S1, vegetative stage), anthesis (S2, reproductive stage), and dual stress condition (S3, combination of vegetative and reproductive stages). Results showed that all of the traits changed differently among hybrids under water stress but recovered close to initial values after re-watering. S3 affected leaf gas exchange and agronomic traits more severely than S1 and S2 treatments. Pn decreased due to imposed drought but more slowly in hybrids SC647 and SC704. In addition, SC700, SC704 and SC647 had the maximum BM and plant height. But, WUE decreased during the water stress period especially in hybrids SC260 and SC370 in which the decrease was remarkable. It can be concluded that SC704 and SC647 were the most tolerant and SC260 and SC370 were the least tolerant hybrids to water stress. The variation observed amongst the evaluated hybrids suggests the existence of valuable genetic resources for crop improvement in relation to drought tolerance.

Water stress is one of the major abiotic stresses in agriculture worldwide. In order to assess photosynthesis response and grain yield of 25 wheat genotypes under water deficit (post-anthesis stress) conditions, a 2-year study (2010-12) was carried out as a split-plot arrangement using randomized complete block design with three replications. The most sensitive gas exchange variable to water deficit was found to be mesophyll conductance (gm) (62% reduction), followed by photosynthesis rate (Pn) (42% reduction). Water deficit also reduced grain yield by an average of 45%. Pn and gm were significantly correlated with grain yield under both conditions. Higher chlorophyll content was associated with higher Pn under water deficit conditions. Maintenance of greater green leaf area during grain filling period was related to greater grain yield. Genotypes with higher Pn and gm were those with optimum grain yield (i.e. cvs. Zarrin and Darya), hence, Pn and gm were found to be the appropriate indices for screening wheat genotypes under the terminal water deficit conditions.

Several saffron ecotypes (Mashhad, Torbat-Jam, Torbat-Haydarieh, Gonabad, Birjand, Ghaen) were evaluated in Urmia for stigma yield and yield components using different maternal corm weights (6, 8, 10, 12 g) in 2013 cropping year. The experiment was arranged as factorial based on randomized complete block design. Analysis of variance showed that there were significant differences among saffron ecotypes and maternal corm weights with respect to all studied agronomical traits. However, there was no interaction between ecotypes and corm weights for the majority of these characters. Torbat-Haydarieh and Mashhad ecotypes, and Gonabad and Ghaen ecotypes had the highest and lowest saffron yield in the Urmia condition, respectively. The yield and yield components of saffron improved when the greater maternal corm weight was used. There were positive relationships between saffron yield and all its components. Based on the stepwise regression analysis, dried stigma weight, stigma length, fresh flower weight, dry leaf weight and leaf length were the main components of saffron yield. We can conclude that maternal corm weight has a very important role in saffron performance. Furthermore, in order to establish a new saffron cultivation, it seems essential to take into account the climate condition of areas from which the corms were selected.

Salinity is one of the major abiotic stresses that severely limit barley production worldwide. In the current research, for mapping the QTLs of agronomic and physiological traits, 149 double haploid (DH) lines from a cross between an Australian cultivar, Clipper (salt susceptible), and an Algerian landrace, Sahara3771 (salt tolerant), were evaluated under natural saline (Yazd Station, ECsoil=10-12.8 ds/m and ECwater=9-10 ds/m) and normal (Karaj Station, ECsoil and ECwater ~2-2.5 ds/m) environments. There were remarkable differences between parents and among the lines for studied traits, including days to heading, relative water content, chlorophyll content, plant height, spike length, days to maturity, biomass, grain yield, harvest index, grain number per spike, 1000 grain weight, Na+ and K+ contents and K+/Na+ ratio. QTL analysis was performed using the genetic linkage map consisted of 517 molecular markers distributed evenly on all seven barley chromosomes spanning 1502 cM of barley genome based on composite interval mapping method. A total of 72 QTLs for the measured traits were determined, from which 40 QTLs were under normal and 32 QTLs were under salinity stress conditions. The phenotypic variation explained by individual QTLs ranged from 2.7 to 61.8%. A major QTL related to biomass, grain number per spike, grain yield, plant height and 1000 grain weight was identified on chromosome 2H in the vicinity of Vrs1 marker locus. In addition, for plant height, biomass, grain number per spike and 1000 grain weight, some stable QTL (s) under both salinity and normal conditions were identified on that locus which considered as salinity related QTLs. These QTLs can be useful in breeding programs for improving salt tolerance using marker-assisted selection.