نشریه علوم به زراعی گیاهی
سال سیزدهم شماره 2 (پاییز و زمستان 1402)

Drought stress and the amount of nitrogen are considered as two factors limiting the yield of corn grain. To investigate the effect of the time of occurrence of drought stress and different amounts of nitrogen on the yield and yield components of corn variety 770 SC, this research was carried out factorial in the form of a randomized complete block design in Three repetitions were carried out in the summer of 2013 in the research farm of the Faculty of Agriculture of the Islamic Azad University, Shushtar branch. The investigated treatments include the time of stopping irrigation in different stages of growth (at the stage of 10 leaves to tassels, stopping irrigation at the stage of emergence of 50% of tassels until the silks turn brown and control without stress) and amounts of nitrogen fertilizer (100, 150 and 200 kg of pure nitrogen per hectare). The results showed that in the treatment of no irrigation in the flowering stage, the grain yield decreased due to the number of seeds in the cob despite the increase in the weight of 1000 seeds. In the full irrigation treatment (control), despite the weight of 1000 seeds being less, but due to the significant increase in the number of seeds in the cob, a higher seed yield was obtained. Increasing the amount of nitrogen under stress conditions caused an increase in the number of seeds, but due to the sensitivity of the reproductive stage to drought stress, the yield of seeds was less than the optimal conditions. Irrigation at the 50% stage until the silks turned brown, the harvest index decreased significantly. The stress in the 10-leaf stage caused a decrease in plant height due to the decrease in cell growth and development. The results of this study showed that in conditions where the plant faces drought stress during the flowering period, nitrogen consumption increases during the vegetative growth stage in order to reduce the effects of stress. Dryness seems beneficial.

The large extent of saline lands in the world, and the increasing demand for food, have necessitated the importance of using appropriate strategies to increase the tolerance of plants to salinity for their cultivation in saline lands. In order to investigate the effect of silica fertilizer on reducing the harmful effects of salinity treatment in radish plant, a pot experiment was designed in the form of a completely randomized design with three replications in Behbahan city in 2021. The treatments included salinity stress at two levels (zero and 200 mM sodium chloride) and silica fertilizer at two levels (zero and 2 g per liter). The results showed that salinity stress caused a significant decrease in photochemical efficiency of photosystem 2 (Fv/Fm), photosynthetic index (PI), and chlorophyll meter number (SPAD) as well as a decrease in root length and plant height. In contrast, silica fertilizer treatment caused a decrease in the harmful effects of salinity stress on them. Based on the correlation results between the traits, a positive and significant correlation was seen between the chlorophyll meter number trait (SPAD) and the photosynthetic index traits, and the photochemical efficiency of photosystem 2 (Fv/Fm). According to the results of the present study, the application of silica fertilizer under salinity stress conditions with a positive effect on the photochemical efficiency of photosystem 2 (Fv/Fm), photosynthetic index, and chlorophyll meter number (SPAD), decrease the harmful effects of salinity stress on radish plants.

An experiment was conducted to investigate the effect of salicylic acid (Sa) and jasmonic acid (Ja) pretreatment hormones on germination and seedling growth of Chamran and Karkheh wheat cultivars under drought stress (St). The cultivars seeds were primed with Ja (100 μM) and Sa (10 mM). St was applied using polyethylene glycol (PEG-6000). The data were analyzed based on a factorial experiment with three replications in a randomized complete block design. The use of Ja and Sa reduced the effects of St on wheat germination indices and the use of Ja was more effective. St reduced germination by 33.45%, while the application of Ja and Sa improved it to 22.5%. Germination seedling stress and seed length vigor index were also decreased by 23.7 and 55% under St compared to the control, but with Ja and Sa application, these indices improved to 20 and 16%, respectively. The sensitivity of Karkheh variety with less accumulation of proline was higher in St conditions and it improved to a great extent with the application of Ja and Sa. It is recommended not to use the Karkheh for the southern and western parts of Khuzestan province, where there is a high probability of St occurrence. Considering the improving effect of Ja and Sa on the germination indices of wheat seeds tested in this study, it is suggested that during additional studies, other seeds of wheat cultivars should also be tested with these hormones for use in tropical areas.