علی قاطعی

The aim of this study was to investigate the relationship between the morphometric characteristics of the seeds of different buckwheat (Fagopyrum esculentum Möench) lots obtained from different planting dates (29th Aug: 1, 13th Sep: 2, 28th Sep: 3 and 12th Oc: 4) with its seed germination quality under different temperature treatments. For each of seed lot, four separate experiments with 11 temperature levels including 4, 7, 10, 15, 20, 25, 30, 35, 37, 40 and 45 °C were carried out in a completely randomized design with 3 replications in seed science and technology laboratory of Agricultural Sciences and Natural Resources of Khuzestan University in 2022. The results of analysis of variance demonstrated that temperature has a significant effect at the level of 1% on germination rate index. According to the model parameters and of course the standard error, the segmented model was chosen as the best model. Based on this, according to the superior (segmented) model, the base, optimal and ceiling temperatures for lot 1 are 4.82, 34.24 and 44.82 degrees Celsius respectively, in lot 2 they are 4.18, 33.82 and 46 respectively. 44.0 degrees Celsius, in lot 3 it was estimated 5, 34.64 and 43.87 degrees Celsius respectively and in lot 4 it was estimated 5, 31.69 and 44.27 degrees Celsius respectively. Identify the cardinal temperatures can be of great help in managing the optimal sowing date of crops.

Among the most common problems and stress in the conditions of Khuzestan province, heat stress at the end of the season and the deficiency of nutrients, which occurs in different periods of rapeseed growth, depending on their severity, causes physiological and metabolic disorders and ultimately reduces the yield of rapeseed plants with different intensity depending on the type of plant genotype, they affect

With the aim of evaluating the growth and yield response of rapeseed cultivars (Brassica napus) to boron element levels in late season heat stress conditions caused by late sowings dates, this study was carried out in a split-split plot arrangement in the form of a randomized complete block design with three replications. The expeiment was carried out in the crop year of 2021-2022 in the research farm of Agricultural Sciences and Natural Resources University of Khuzestan. Sowings dates (November 21, December 11, and December 31) in the main plots, four levels of boron (zero, 4, 8, and 12 kg/ha) in the subplots and rapeseed cultivars (RGS, Zafar, and Saffar) in the sub-sub-plots were investigated.

The results of the research showed that sowing date and end of season heat stress in Khuzestan conditions had a significant effect on most of the studied physiological traits, seed yield and biological yield. In addition, the effect of boron on traits such as leaf area index, leaf area ratio, and relative moisture content of leaf water, leakage of electrolytes, grain yield and biological performance was significant. The triple interaction effect of planting date, boron and variety was also significant on traits such as relative moisture content of leaf water, leakage of electrolytes, grain yield, and biological performance. So that with the delay in planting and the consequent increase in temperature and heat stress at the end of the season in the period of growth of the rapeseed plant, it causes a decrease in traits such as leaf area index, relative moisture content of leaf water, leaf area ratio, leaf specific area, seed yield and biological yield. And conversely, due to the heat stress at the end of the season, the leakage of electrolytes and the canopy temperature increased significantly. In general, the highest seed yield was obtained in Safar variety on the sowing date of December 11 and the boron level was 4 kg/ha with an average of 4590 kg/ha. Also, the highest average leaf area index was observed on the first sowing date and Safar variety with an average of 5.43 and the lowest value was observed on the third sowing date and Safar variety with an average of 2.11. It was also observed that the application of boron caused a significant decrease in the leaf area index in all three studied cultivars. This issue can indicate the lower need of boron consumption of the studied cultivars in this experiment.

In general, the heat stress at the end of the season, which occurs in different periods of rapeseed growth, especially the seed filling period, depending on its intensity, causes physiological disorders in the plant and finally affects the grain yield with different intensity and depending on the genotype of the plant. The analyzed rapeseed genotypes also showed tolerance to different levels of boron element in the heat stress conditions of the end of the season and showed different reactions with different amounts of boron consumption per hectare.

In order to study germination characteristics of wheat seeds Chamran cultivar of wheat obtained from Plant that treated with different levels of nitrogen and spraying cytokinin under heat stress conditions, this research carried out in factorial experiment in randomized complete design with four replications at seed technology laboratory of Agricultural Sciences and Natural Resources University of Khuzestan. In both conditions Normal (optimum planting date) and Terminal heat stress (late planting date), nitrogen (N) was in four levels (0, 75, 150, and 225 kg.ha-1) and cytokinin (Ck) was in three levels (0, 50 and 100 µM). The results showed Effect of planting date was effective significantly on all traits, with the exception of hypocotyl dry weight. The cytokinin (Ck) was effective significantly only on germination percentage, germination uniformity, D90, Length vigor index, SRUE and thousand grain weights. Results of interaction showed treatment of N× planting date had the most Germination rate (0.03 per day). The most mobility of seed reserves (1.6 mg per mg seed) and seed vigor (17.19) was obtained from high levels of N×CK treatment. The effect of N ×Ck× planting showed the most germination (100%) was obtained from high levels of N×Ck treatment and the less germination percentage (66%) was obtained from treatment of late planting date and 150 kg ha-1 N and without cytokinin. so cytokinin increased the resistance of wheat against terminal heat stress and increased germination percentage of seed produced.

In order to study effect of salinity and drought stress on germination and Seedling growth and fitness model hydrotime and threshold tolerance to salinity in two different species Basil, a factorial experiment in a randomized completely design was conducted at University of Mohaghegh Ardebili in 2015. Experimental treatments included was two species of basil (Purple basil and Red basil), different salts (Manitol, NaCl+K2SO4, K2SO4 and NaCl) and different potentials (0, -3, -6 and -9). Model output result showed, germination rate in drought stress coundition on Red basil (θH= 37.32) highest than Purple Basil (θH= 37.32) and uniformity of germination in purple basil (σψb=3.37) less than Red basil (σψb=1.44). Also Red basil higher tolerance drought compared with Purple basil. Threshold tolerance to salinity in germination stage showed, in Purple Basil at NaCl, K2SO4 and NaCl+K2SO4 had threshold tolerance -0.59, -0.13 and -0.87 bar and in Red Basil equle -0.31, -0.25 and -2.88 . Salinity and drought stress were causing reduced in the seedling growth and seed vigor index. The most (0.92) and least (0.78) on the use of the reserves in the case of purple basil of NaCl and NaCl + K2SO4, respectively, was observed at the same time. This is while that, the highest use of the reserves on the red basil K2SO4 salt and least amount was obtained application of NaCl. The highest vigor weight index of purple basil was observed of zero osmotic potential. The least weight index purple basil was obtained of the potential -9 bar Mannitol.

To study effects of different levels of nitrogen fertilizer and cytokinin on some physiological traits of wheat cv. Chamran under normal and post anthesis heat stress conditions, this experiment was conducted at Ramin Agriculture and Natural Resources University, Ahvaz, Iran, in 2012-2013 growing season. The experiment was carried out in two separate factorial experiments using randomized complete block design with four replications.The first experiment was planted in normal date of sowing (05 December 2012) and the second experiment was planted late (20 January 2013) to expose the experimental treatments to terminal heat stress. In both experiments, nitrogen (N) was applied at four levels (0, 75, 150, and 225 kg.ha-1) and cytokinin (Ck) at three levels (0, 50 and 100 µmol). Results showed that intraction effect of sowing date× nitrogen× cytokinin on prolin content and SPAD value, intraction effects of nitrogen × cytokinin and sowing date × nitrogen on FLAD (Flag Leaf Area Duration), stomatal conductance and grain yield was significant. The highest grain yield was obtained from application of 150 kg.ha-1 nitrogen and 100 µmol cytokinin, however, it was not significantly different from 225 kg.ha-1 nitrogen and 100 µmol cytokinin and 150 kg.ha-1 nitrogen and 50 µmol cytokinin. It was concluded that with increasing application levels of nitrogen and cytokinin the negative effects of terminal heat stress could be mitigated.

In order to evaluate the effect of hydro priming on seed germination of Vigna radiata under salinity stress an experiment was arranged in a factorial based on a completely randomized design with three replications in laboratory of the Agricultural College of the University of Ramin Khuzestan. Treatments were salinity stress at 4 levels (0, 3, 6 and 9 Mmhos) and hydro priming at 3 levels (1, 1.5 and 3 h) and two sizes of seed (small and large seeds) that was carried out by NaCl. Results showed that all of germination characteristics decreased with increased salinity, but this decrement for seeds that primed at long time, was less. Also at all characteristics, small seeds, showed better reactions than large seeds. Generaly hydropriming was improved germination characteristics of Vigna radiata under saline conditions. According to this experiment, hydropriming improved germination and establishment.

Grain yield of bread wheat (Triticum aestivum L.) is reduced by heat stress، particularly when occurs in reproductive phase، in many countries worldwide، including Iran. In order to study the effects of different levels of nitrogen and cytokinin on wheat yield and yield components at normal and heat stress conditions in Khuzestan، Iran، this research was conducted at Ramin Agriculture and Natural Resources University in 2010-2011. This study was carried out in two separate factorial experiments in randomized complete block design with four replications. The first experiment was planted in a normal date and the second experiment was planted late (Terminal heat stress). In both experiments، nitrogen (N) was applied in four levels (0، 75، 150، and 225 kgha-1) and Cytokinin (Ck) sprayed in three levels (0، 50 and 100 µM). The results of both experiments (normal and stress conditions) showed that by increasing the N rate، the grain yield (5652. 1 and 3874. 7 Kg/ha respectively)، biological yield، number of spikes per m2، spikelet’s per spike، grains per spike were significantly (p<0. 01) increased. Application of Ck at normal sowing date increased the grain yield (4856. 7 kg/ha) and 1000 grain weight (41 gr) significantly (p<0. 01) and at late sowing date only increased 1000 grain weight (30. 2 gr) significantly (p<0. 01). Application of N and Ck in both experiments significantly increased grain yield (p<0. 05) and only at late sowing date increased 1000 grain weight significantly (p<0. 01). Based on our findings، application of N and Ck may lead to the amelioration of terminal heat stress effects on bread wheat in hot regions such as Ahwaz.