seyed ataallah siadat

Drought stress is one of the most important abiotic stresses that can seriously reduce crop yield depending on the season, intensity, and time of occurrence. Corn (Zea mays L.)  cultivation and production in Khuzestan province face limitations such as lack of water resources in summer, low percentage of soil organic matter, heavy soil texture, and soil salinity that one of the reasons for which is the excessive use of chemical fertilizers, which can reduce some of these problems by using crop management and breed methods. Using compost fertilizer has beneficial effects on the physical, chemical, and biological conditions of the soil and has positive effects on grain yield and yield components of crop plants. Also, one of the factors affecting the growth and development of crops is the method and pattern of cultivation, which affects the distribution of plants in the field, distances between plants, the use of growth sources such as light, water, and soil nutrients, competition between plants, etc. that finally, these factors affect the growth and yield of crops. This study was designed with the aim of investigating the response of silage corn to the effect of the place of cultivation and different replacement ratios of nitrogen fertilizer and organic fertilizer (sugarcane (Saccharum officinarum L.) residue compost) under drought stress conditions in the Agricultural Sciences and Natural Resources University of Khuzestan.

This experiment was conducted as a split split-plot arrangement in a randomized complete block design with three replications in the summer of 2021 in the experimental farm of the agricultural college of Ramhormoz in Khuzestan province. Experimental factors including irrigation regimes at three levels; Irrigation after draining 30% of available moisture in root development depth (I1: control irrigation), irrigation after draining 50% of available moisture in root development depth (I2: mild stress) and irrigation after draining 70% of available moisture in root development depth (I3: severe stress) in the main plots, five fertilizer treatments including the complete supply of nitrogen required by the plant through chemical nitrogen fertilizer (N1) (180 kg.ha-1 nitrogen), 75% nitrogen+ 25% compost (N2) (135 kg.ha-1 nitrogen+ 12.5 ton.ha-1 compost), 50% nitrogen+ 50% compost (N3) (90 kg.ha-1 nitrogen+ 25 ton/ha compost), 25% nitrogen+ 75% compost (N4) (45 kg.ha-1 nitrogen+ 37.5 ton/ha compost) and the complete supply of nitrogen required by the plant through the sugarcane residues compost (N5) (50 ton.ha-1 compost) in the sub plots and the planting site was by two methods of planting on ridges (P1) and planting in furrows (P2) in the sub-sub plots.

Variance analysis showed that the effect of different levels of drought stress caused by different irrigation regimes, ratios of chemical and organic fertilizer replacement and cultivation methods was significant on all the measured traits. A mean comparison of the interaction effect of the cultivation method and combined application of nitrogen fertilizer and sugarcane residue compost under drought stress conditions showed that the treatment of 50% chemical fertilizer+ 50% organic fertilizer (consumption of 180 kg.ha-1 of nitrogen fertilizer and 25 tons.ha-1 of sugarcane residue compost) compared to other treatments, caused a significant increase in total fresh yield and total dry yield of corn. Under favorable irrigation conditions, the chemical nutrition treatment resulted in the highest total dry yield, with the combined nutrition treatments ranking next. However, under conditions of mild and severe drought stress, the combined nutrition treatments produced a higher yield compared to both the chemical and organic treatments.

In general, based on the results of this experiment, it seems that the integrated application of chemical fertilizer along with organic fertilizer with the providing of nutrients, their gradual release, and maintaining moisture in the soil and planting in furrows by maintaining more moisture and creating a suitable microclimate for the plant has developed growth, moderated drought stress, and increased corn yield.

Increased drought to maintain the water potential in plant causes a reduction in diameter of Xylem vascular bundles (Majd et al., 2009). Xylem vascular bundles area decreases in different conditions leading to water stress in order to improve irrigation efficiency and to maintain plant water potential (Limouchi & Farahvash, 2014). Stresses can decrease vascular bundles area and diameter to improve water use efficiency and to reduce transpiration, while these traits are positively and significantly correlated to grain yield (Limouchi, et al., 2013). Water shortage for rice leads to a reduction in the value of anatomical traits effective in water retention and movement such as vascular bundles to maintain the amount of water in rice (Dawood, 2016). This study aimed to identify the tolerance and sensitivity mechanisms to drought in different irrigation intervals in order to increase grain yield by examining changes in anatomical characteristics of leaf stamen.

This study was performed by split-split plots using randomized complete block design with three replications in Khuzestan province with the aim of determining the best Planting pattern and Hormone Treatment of rice cultivation in two years (2018 and 2019). Three planting methods (planting drying, planting seedlings, planting direct or common), 16 different levels of auxin and salicylic acid hormones in the form of seed priming and different leaf spray treatments with 1 and 2 liters per hectare and different spraying times in the tillering stages and The appearance of panicle on different rice genotypes was investigated.

The combined analysis results showed that in addition to the interaction effect of planting method in hormone traits, the level of large vascular bundles in other cases, the main and interaction effects of traits, there is a significant difference in the level of probability of one percent. The highest level of vascular groups in seedling cultivation was obtained due to optimal management and priming with auxin and salicylic acid due to the greatest effect on the plant. Also, the level of these traits was lower in genotypes with higher resistance, which can be one of the main mechanisms of the plant in terms of increasing adaptability and maintaining more water potential within the plant under stress conditions. Finally, the highest levels of large and small vascular panicle with mean 12348 and 1928.792 micrometers were obtained in IR 80508-B-194-3-B genotypes and red spider in the said treatments, respectively. The surface of large vascular bundles had the highest positive and significant correlation (0.124**) with grain yield in terms of its high level in water and food transfer. The obtained results can be one of the main goals in breeding research and modification of cultivars with higher resistance to salinity conditions under the influence of different hormonal treatments and planting patterns.

The results of this study showed that an increase in Hormone and irrigation intervals and thus increased drought had reduced vascular bundles area, which can be a mechanism to maintain water and cells turgidity pressure.Keywords: salinity stress, Rice, Vascular, Planting pattern, Hormone, Priming, Leaf.References:Dawood, M.G. 2016. Influence of osmoregulators on plant tolerance to water stress. Scientia Agriculturae, 13 (1): 42-58. Limouchi, K. 2013. Effect of Different Planting Dates on the Anatomy of the Flag Leaf and Grain Yield of Rice Varieties in the Khuzestan Region, Iran. International Journal of Biology, 2 (2): 19-27. (in Persian with English abstract).Limouchi, K., and Farahvash, F. 2014. Effect of different planting dates on anatomy of the peduncle and grain yield of rice varieties in the north Khuzestan region. India Journal of Sciences Research and Technoloji, 2 (2): 99-103. (in Persian with English abstract).Majd, A., Jonobi, P., and Zanipour, M. 2009. Effects of drought stress on anatomical structure of the sunflower plant. Developmental Biology, 1 (4): 11-24.

Accurate prediction of seedling emergence in the field is crucial for the performance of growth models. In order to determine thresholds of seedling emergence response to temperature, two replicated field experiments were carried out at Ramin Agriculture and Natural Resource University of Khuzestan during 2015-2016 and 2016-2017. In these experiments, seedling emergence of two spring canola cultivars (Hyola 401 and Sarigol) was evaluated in a randomized complete block design with four replications in fifteen planting dates (as environment). Thermal-time model was developed based on the Weibull probability distribution function, and thermal thresholds for seedling emergence response of two spring canola cultivars in field conditions was modeled based on this function. Based on model outputs, the base temperature for seedling emergence (Tb) was estimated to be 5.83 °C in the hybrid Hyola 401 and 4.16 °C in the cultivar Sarigol. The thermal-time required to initiate seedling emergence at sub-optimal temperature range (θT(0)) and the thermal-time needed to complete seedling emergence at supra-optimal temperature regimes without significant differences between two cultivars was estimated to be 55.5 and 5.65 °C d, respectively. Maximum temperature for the 50% probability of the thermoinhibition of seedling emergence (Tm(50)) in hybrid Hyola 401 and cultivar Sarigol was estimated to be 33.02 and 33.30 °C, respectively. The optimum temperature for 50% seedling emergence in the field (To(50)) for hybrid Hyola 401 and cultivar Sarigol was determined to be 30.99 and 31.22 °C, respectively.

Rice can be irrigated like wheat and corn as an aerobic plant (1 and 3). Studies show that at certain stages of plant development, materials development, production photosynthetic processes are surplus to requirements. This material is for Ghyrsakhtmany compounds in plant vegetative organs such as stems, pods and leaves are stored and to pursue the establishment of a strong physiological destinations, during remobilization to the grain moves (2). Potential remobilization is a physiologically acceptable index to a variety of factors including genotype and lack of water or too dependent (4). With regard to water crisis, it’s essential to increase knowledge level and awareness about water tension loss. This study aims at realization of this purpose and reducing the negative effects of water tension. An experiment Was carried out Study of irrigation regimes on rice genotypes remobilization and grain yield of Khuzestan province in a split-plot arrangement using randomized comlete bloks design with three replication in 2014 and 2015 cropping seasons at Shavoor Agricultural Research Station, Dependent in Research Center of Agricultural and Natural Resources of Khuzestan. For exposing rice genotypes to Four different irrigation regimes (1, 3, 5 and 7 days), and 12 genotypes were randomized in sub-plots. The combined analysis results showed that all of these attributes among different irrigation regimes, genotype and interaction of two factors have significant difference, at the level of five percent and in property remobilization efficiency, between the irrigation regimes and this story was true for other levels and the qualities at one percent level. And only in the interaction of two factors of irrigation regime and total genotype distribution, no statistically significant difference was observed. The amount of remobilization, apart from the leave that saw decrease from Flood irrigation regime to 3-day period, in the other organs saw increase and then by increasing the number of decreasing irrigation intervals, according to the dry matter of organs. Regarding the efficiency of remobilization, apart from the leave that experienced a decreasing trend from flood irrigation regime to 5-day irrigation period, and then in 7-day irrigation period it experienced an increasing trend, while stem experienced a totally an inverse trend. The share of Leaves in redistribution share of three-day irrigation frequency decreased and then increased with increasing and decreasing irrigation, in a way that inverse share of stem and total had the largest share under the condition of increased drought around the plant by seven- day irrigation period. And the ability and difference of leave source could be the reason for its being different from the other organs. Probably due to low tank volume and reduced ability to produce the active tank, the main factor is reducing the amount of supply, efficiency and contribution of remobilization in irrigation regimes. Correlation coefficients show that grain yield with greatest average of 6555.10 kg per hectare in second irrigation regime with three-day irrigation period in the genotype IR 81025-B-327-3. Biggest significant and positive correlation was with panicle redistribution (0.207**), stem (0.136*) and total (0.129*) but the other attributes had negative correlation with the grain yield. According to the results stem maximum value, efficiency and remobilization of dry matter in the main sink plant, The genotypes with greater resistance and frequency of irrigation regimes with one, three and five days filling an important role in providing seed, and this could be one of the reasons for the superior yield of these genotypes is under irrigation

An experiment was carried out to study of heat stress on assimilate remobilization of rice in north of Khuzestan province in a split-plot arrangement using randomized complete blokes design with three replication in 2006 and 2007 at Shavoor Agricultural Research Station, Dependent in Research Center of Agricultural and Natural Resources of Khuzestan. For exposing rice cultivars to different higher temperature regimes, main plot were assigned to three sowing dates from 5 May, 26 May and 16 Jun and cultivars were; Hoveizeh, Hamar (heat tolerance) Ghermez Anbori, Champa (heat sensitive) and Danial (relatively heat tolerant) were in sub-plots. Results showed that the highest dry matter redistribution was in Ghermez Anbori and heat tolerant cultivars. The grain, stem and leaf portions were significant on sowing date and cultivars. The second and third planting dates and heat tolerant cultivars had higher content. The highest remobilization, current photosynthesis and the portion of organs in filling grain yield were 1140.8 kg.ha-1, 3923.3 kg.ha-1, and 22.5%, respectively, in 26 May planting. But the highest share portion of current photosynthesis in grain yield was in 5 may in the planting date.

In order to evaluation of trend yield and physiological indices variation of some current Rice cultivars an experiment was carried out in split-plot arrangement using randomized complete blocks design with three replication. In 2006 and 2007 years at Shavoor Agricultural Research Station in Khuzestan province. For exposing rice cultivars to different higher temperature regimes, main plots were assigned to three sowing dates from 5 May with 20 days intervals and cultivars namely: Hoveizeh, Hamar (heat tolerance) Ghermez Anbori, Champa (heat sensitive) and Danial (relatively heat tolerant) were randomized in sub-plots. The results of combined analysis of variance showed that the highest grain yield was harvested from the second sowing date (26 May). It was the superior to first sowing date (5May) with 62.5 percentages. The reason of higher yield related to superior physiological indices in panicle exertion, LAD in ripening duration and also higher dry matter storage potential. In among cultivars, Hoveizeh was the superior to other cultivars and had higher yield related to Ghermez Anbori, Champa with 50.9 and 36.3 percentage respectively. In spite of heat sensitive cultivars had higher of Maximum leaf area index but their's crop growth rate, net assimilation rate and relative growth rate were lower.

In order to evaluate the best sowing date and its effect on yield and yield components of sunflower cultivars, a field experiment was done as split block design in a randomized pattern of complete block design with three replications in 2009 in Shahinshahr , Isfahan. The sowing date was studied in four intervals : 22 June,2009, 1 Jul,2009,11 Jul,2009, and 21 Jul 2009. The four factors used were, Alestar, Azargol, Master and Zaria. The results showed that sowing date had a significant effect on the number of seed, weight of thousand seeds, seed yield, LAI, Cap diameter and oil percentage. The higher seed yield (4170 kg/ha) was obtained from the first sowing date (22 June.2009), and the lowest seed yield (2230 kg/ha) was obtained from the last sowing date (21 Jul.2009). The average of seed yield in 1 Jul.2009 and 11 Jul.2009 was 3980 and 2760 kg/ha. The highest number of seed (759.5) and weight of thousand seeds (55 gr) was obtained from 22.June.2009 and the lowest number of seed (619.3) and weight of thousand seeds (36 gr) was obtained from 21.Jul.2009. The cultiver had a significant effect on all studied traits except the number of seeds. The highest and lowest seed yield were related to Azargol (4090 kg/ha) and Alestar (2450 kg/ha). The seed yield of Zaria and Master were 3500 and 2910 kg/ha. The highest and lowest weight of thousand seeds was obtained from Azargol (57 gr) and Alestar (38 gr).