نشریه فیزیولوژی محیطی گیاهی
پیاپی 58 (تابستان 1399)

Salinity is a major environmental stress that causes severe damage to crops and horticultural crops and also reduces plant biodiversity. In order to study the resistance to salinity during seed germination and early growth, 18 strains of wheat cultivars (Triticum aestivum L.; Including car, non-indigenous and hybrid carcasses) were investigated at four levels of control, 100, 200 and 250 mM sodium chloride. The experiments were conducted with a complete randomized block design in three replications in the research laboratory of department of Biology, University of Isfahan, 2015. The results showed that with increasing NaCl level in the culture media, germination indices were affected with more intense. Comparison of mean traits showed that different cultivars of wheat had different reactions. These cultivars were classified in two groups, so that Sorghtoghm, Hamon, Sivand, Bezostaya, Sepahan and Roshan were placed in resistant groups and Ghods, Guspard, Karaj and Navid cultivars were placed in sensitive and low dendrogram groups. Sorghtoghm and Ghods were shown to have the highest and lowest index for germination stress index (GSI) and salinity tolerance index (STI) respectively. The results showed that the different levels of salinity had significant effects on germination percent, germination rate, seedlings stem and root length, root, and shoot dry weight. All measured variables showed a significant decrease with increasing salinity level.

At this study, the effect of drought stress on some agro-physiological characteristics of 15 sunflower genotypes including three check cultivars, eight inbred lines and four synthetic cultivars was evaluated using Randomized Complete Blocks Design (RCBD) with three replicates under non-stress and drought stress conditions at Dryland Agricultural Research Sub-Institute (Sararood Station), AREEO, Kermanshah, Iran during 2013-2014 cropping year. The mean kernel yield of genotypes was 715 and 597 kg/ha under non-stress and stress conditions, respectively which shows a 19.02% reduction due to drought stress. Check cultivar “Zaria” and line “Sil-292” had the highest percentage of yield loss with more than 30%. Synthetic cultivars “Sil-94”, “Sil-54” and “Sil-96” had the lowest percentage of reduction with less than 5%. Kernel oil content ranged from 45.5 to 51.7% in non-stress conditions and from 35.4 to 49.9% in drought stress conditions. Drought stress caused about 10% decrease in kernel oil of the genotypes. Overall, drought stress caused early flowering, reduced agronomic and morphological traits and kernel oil content and increased relative electrolyte leakage and leaf relative water loss. Genotypes “SIL-54”, “SIL-42”, “SIL-140” and “SIL-237” were recognized as the most tolerant genotypes using ranking method and its parameters. These genotypes were identified as the best genotypes based on the biplot diagrams under the both conditions.

The study of various affecting factors in order to promote seedling growth at nursery and afforestation areas is very important. Although silicon is not recognized as an essential element in plants, it has very beneficial effects on plant species. For this purpose, an experiment was conducted following a completely randomized design with 5 treatments to evaluate different concentrations of silica on some growth parameters and nutrient uptake in Iranian oak seedlings. For each treatment, 10 pots were considered and treatments were performed including control and irrigation treatments with concentrations of 50, 150, 350 and 500 mg L-1 silica (based on field capacity). The result showed that silica had no statistically significant effect on basic diameter but root volume and stem diameter in seedlings treated with 500 mg L-1 were greatre around more than 50% in comparison with control seedlings. On the other hand, seedlings treated with 500 mg L-1 silica had the highest dry biomass compared to control and other treatments so that the leaf, stem and root biomass of the treatment were higher around 68-80% than control seedlings. The highest absorption of nitrogen, potassium and calcium were observed in 150 mg L-1 treatment. However, at low concentrations, silica decreased the uptake of manganese, copper and zinc and decreased the amount of iron uptake in the presence of silicon. Finally, it can be concluded that the use of silica in this study increased the total biomass of oak seedlings and also increased the absorption of macro elements so, the finding can be considered in forest nursery to seedling production. Nevertheless, further studies are needed to understand its mechanism, including gene and protein expression analysis.

In order to investigate the response of 15 maize S6 lines to drought stress, a split plot design based on randomized complete block design with three replications was conducted in 2015 year at the research field of Graduate University of Advanced Technology, Kerman, Iran. In this study, the main factor was stress at two levels (normal with five days irrigation and low irrigation with ten days irrigation) and the sub-factor was maize line at 15 levels. The results showed that there were significant differences between stress levels and lines for all studied traits (chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, soluble sugars, protein and proline content). Mean comparison of lines showed that lines 9, 3 and 5 had the highest proline content under drought stress conditions. The lowest phenotypic coefficient of variation was for total protein (2.59) and the highest for proline (74.17). Cluster analysis divided the studied lines into four, five and six groups in normal, drought and mean conditions, respectively, and the similarity of their grouping was high. Based on the results of cluster analysis and mean comparisons, lines with high genetic distance were grouped together. Thus, three groups, each with five lines, were found to be used in the planning of breeding projects and cross-breeding programs. Line 9 also showed a high mean for most of the studied traits in both conditions and it can be considered as a promising line in future experiments.

Possibility of the growth, biomass and photosynthetic pigment content fluctuations were surveyed in the soil cyanobacterium Calothrix sp. FS 65 via the combinations of two parameters means different concentration of salinity (17 , 80 and 160 mM) and time (24 and 96 hours). After purification, axenic culture of the cyanobacterium was pretreated with 24 and 96 hours in 17, 80, and 160 mM NaCl and then moved to usual culture media without extra salinity. Analysis included survivality and growth, in vivo pigment (phycocyanin, allophycocyanin, phycoerythrin and chlorophylls) and comparison of the combination of time and salinity on photosystem ratios. Results showed that the 24 hours pretreatments cause the complete deletion of the lag phase of the growth curve of such a strain. This may be an outstanding result regarding the role of lag phase on the acclimation processes and essential compartments of the nitrogenase and meanwhile intelligent outer layers envelopes. The main components of phycobilisomes means phycocyanin, phycoerythrin and allophycocyanin increase more than sixty percent after 96 hours pretreatment in 160 mM salinity. The phosystems ratio reached to the maximum at 24 hours after 17 mM salinity and then decreased significantly at the 96 mM at 96 hours after inoculation. The difference between the intercalary times and treatments seems insignificance despite that there was obvious difference. Collectively, using pretreatments may have considerable effects on the energy transfer in photosystems and the production of the energy and reductans which seem the great advantageous for the large scale cultivation technology.

In order to study the effects of irrigation and abscisic acid regime on physiological factors and gas exchanges of Lavandula angustifolia CV. Organic Munestead, a pot experiment was conducted as factorial based on randomized complete block design with three replications at Plant Production faculty of Gorgan University of Agricultural Sciences and Natural Resources, during growing season of 2016- 17. The treatments were four levels of irrigation regimes (30-40, 50-60, 70-80 and 90-100 percent field capacity) and Abscisic acid including three levels (0, 15 and 30 Mm/L). The results showed that irrigation regimes increase chlorophyll a, chlorophyll b, chlorophyll a+b, gas exchange and RWC. Abscisic acid had significant effect on all traits except of carotenoid content that except to efficiency of water consumption was Abscisic acid 15 Mm/L, the others were the highest in Abscisic acid 30 Mm/L. Also interaction effect of irrigation regimes and Abscisic acid was significant for all traits except of chlorophyll a+b. Abscisic acid 15 Mm/L spray and irrigation regimes 30-40 percent field capacity increase 25.04 and 38,75 in efficiency of leaf water consumption and efficiency of water consumption, respectively. Generally, Abscisic acid 15 Mm/L application and irrigation regimes 30-40 percent field capacity Introduces the best treatment, due to the lower consumption of water and the use of Abscisic acid in stress conditions, higher levels of Abscisic acid can be achieved in inducing drought tolerance.

Proper harvesting time plays an important role in maintaining fruit quality during storage. Early or delayed harvesting results in unpleasant taste, inability to store and inappropriate appearance. In order to evaluate the effects of harvest time and storage period on physiological and biochemical parameters was conducted with three replications. Tests were carried out with four harvesting time (Based on the total soluble solids (TSS) index), i.e., 5, 6.5, 8 and 9.5 °Brix and four storage time, i.e., 0, 30, 60 and 90 days. Based on the experimental treatments, traits such as fruit juice, TSS, TA, TSS/TA ratio, starch and protein content, fruit pigments, phenolic compounds, antioxidant activity, vitamin C, total sugar content and reducing sugars content in fruit were measured. The results showed that in all harvesting treatments, increasing the storage period significantly increased TSS, TA, protein content, total phenol, vitamin C, total sugar content, reducing sugar and antioxidant capacity. Chlorophyll a, b, total chlorophyll and carotenoid contents increased significantly with increasing harvest index and storage period. The results of this study showed that 60 and 90 days storage periods play an important role in increasing physiological and biochemical indices of kiwifruit (except traits such as fruit juice, starch content, TSS/TA ratio and superoxide dismutase activity) in all harvest treatments.

The yield and quality of tea depend on the shoot growth and bud dormancy. Tea (Camellia sinensis) is one of the natural sources of bioactive compounds, such as caffeine, catechins, and antioxidants, which is consumed as a “health drink” due to its beneficial medicinal properties. The bud dormancy increases the distance of leaf plucking and reduces the yield of tea. In this study, activities of antioxidant enzymes were assessed in banjhi and active buds in two cultivars, clone 100 and hybrid. The results showed that there were significant differences in antioxidant enzyme activity, indicating genetic diversity between them. The activities of enzymes such as ascorbate peroxidase, catalase and peroxidase in the banjhi buds were higher than the active buds, however, in banjhi buds, the peroxidase activity was higher than the active budsThe yield and quality of tea, which is consumed as a “health drink”, depend on the shoot growth and bud dormancy. The bud dormancy increases the distance of leaf plucking and reduces the yield of tea. In this study, activities of antioxidant enzymes were assessed in banjhi and active buds in two cultivars, clone 100 and hybrid. The results showed that there were significant differences in antioxidant enzyme activity, indicating genetic diversity between them. The activities of enzymes such as ascorbate peroxidase, catalase and peroxidase in the banjhi buds were higher than the active buds, however, in banjhi buds, the peroxidase activity was higher than the active buds. According to the results, it seems that biochemical changes are involved in the development of banjhi bud and active bud and these changes can be used as a biochemical marker not only in detecting the yield of tea cultivars but also in reducing the dormant periods.