Limited water stress is one of the most important environmental stresses that affect the growth, quantity and quality of agronomic crops. This study was undertaken to investigate the effect of foliar applied salicylic acid (SA) on physiological responses, antioxidant enzymes and qualitative traits of Cucurbita pepo L. Plants exposed to water-stressed conditions in two years of field studies. Irrigation regimes at three soil matric potential levels (−0.3, −1.2 and −1.8 MPa) and SA at four levels (0.0, 0.5, 1.0 and 1.5 mg/L) were considered as main plot and sub-plots, respectively. The soil matric potential values (MPa) was measured just before irrigation. Results showed that under water stressed conditions alone, the amounts of malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and ion leakage were higher compared with control treatment. However, spraying of SA under both water stress and non-stress conditions reduced the values of the above parameters. Water stress increased CAT, APX and GR enzymes activity. However foliar application of SA led to the decrease of CAT, APX and GR under all soil matric potential levels. The amount of carbohydrates and fatty acids increased with the intensity of water stress and SA modulated this response. By increasing SA concentration both in optimum and stress conditions, saturated fatty acids content decreased. According to our data, the SA application is an effective approach to improve pumpkin growth under water stress conditions.

Safflower (Carthamus tinctorius L.), adapted to arid and semiarid regions, is grown for seed and petal production, but the present study aimed to evaluate the possibility of simultaneous forage and seed production in the autumn and middle types of safflower varieties in dual-purpose cultivation in semiarid areas in the shortfall forage period. An experiment was done based on a randomized complete block design with nine treatments and three replications at the Seed and Plant Improvement Institute, Agriculture Research, Education and Extension Organization, Karaj, Iran. The treatments included the cultivation of Parnian, Goldasht, and Golmehr varieties with the purpose of seed harvesting as control treatments; the same varieties (Parnian, Goldasht, and Golmehr), once with the aim of forage harvesting at 50% stem elongation stage and seed harvesting; and again with the aim of forage harvesting at 50% branching stage and seed harvesting. The results showed that forage harvesting at the 50% branching stage significantly increased the dry and fresh forage yield compared to the 50% stem elongation stage. The highest fresh and dry forage yields (DFY) (42,229 and 11,266 kg/ha) were related to the Golmehr variety at the 50% branching stage. Forage harvesting at the stem elongation stage decreased the crude protein, protein content, and digestibility compared to the branching stage in three safflower varieties. Parnian variety had the maximum seed yield (2,226 kg/ha) without forage harvesting. The highest seed yield in the second year (2018–2019) of the experiment belonged to the Golmehr variety (1,310 kg/ha) to harvest forage at 50% stem elongation (rapid stem growth) and seed harvest treatment, which compared to the first year (2017–2018), showed an increase of 25%. Finally, the forage harvested amount of all three varieties studied was higher in the branching stage than in the stem elongation stage. These results implied that the Golmehr variety (11,266 kg/ha DFY and 520 kg/ha seed yield) is for dual-purpose cultivation, and the Parnian variety (2,226 kg/ha seed yield) is suitable for only seed production for the semiarid region of Karaj in Iran and similar areas in terms of climate.

This study was conducted to investigate the effects of salicylic acid and harvest date on the yield and biochemical and physiological characteristics of peanuts in different humidity conditions, which is the novelty of this research. For this purpose, a split-plot factorial design during the 2018 and 2019 cropping seasons was conducted based on a randomized complete block design with three replications at the experimental field of the Agricultural and Natural Resources Research and Education Center of Guilan Province, Astara, Iran. Humidity regimes included rain-fed conditions (no irrigation), irrigation at the 10% flowering stage, 10% pod formation stage, and 10% flowering stage +10% pod formation stage in the main plots, and three salicylic acid levels (100, 200, and 300 µmol/l), and harvest dates (August 22, September 6, and September 21), were placed in subplots. Drought stress reduced the Chlorophyll Index, relative water content, seed, and pod yield but increased proline, Antioxidant enzyme activity, soluble sugar content, and H₂O₂content. Conversely, Supplementary irrigation decreased proline, antioxidant enzyme activity, soluble sugar content, and H₂O₂content, which increased the Chlorophyll Index, relative water content, seed, and pod yield. Also, salicylic acid foliar application enhanced guaiacol peroxidase, polyphenol oxidase, and ascorbate peroxidase antioxidant enzyme activity, mitigating the undesirable impacts of water deficiency. The maximum pod and seed production was obtained in all humidity conditions with 300 µmol/l salicylic acid. Under Humidity stress conditions, if water resources are available, two supplementary irrigations at 10% flowering and 10% pod formation stage are recommended. Also, for humid climates such as Astara and similar regions, in terms of climate, with limited rainfall in June and July (rainfall less than 10 mm during flowering and podding stages), one supplementary irrigation at 10% pod formation stage is recommended.

This experiment carried out as split plot factorial based on randomized complete block design with three replications in Astara, Iran, during 2018 and 2019 cropping seasons. Irrigation (IR) regimes including IR after 25 mm (IR ₂₅ ), 50 mm (IR ₅₀ ), 75 mm (IR ₇₅ ) and 100 mm (IR ₁₀₀ ) evaporation from Class A pan in main plot, ethanol (ET) including 10 (ET ₁₀ ), 20 (TE ₂₀ ) and 30 (ET ₃₀ ) % (v/v) and Zinc (Zn) fertilizer including 0.5 (Zn _0.5 ), 1 (Zn ₁ ) and 1.5 (Zn _1.5 ) ppm as factorial 3×3 in sub plot, comprised experimental treatments. The results indicated that drought stress decreased peanut SY and full irrigation produced the maximum SY. Nonetheless, the foliar spraying of ET20 and Zn1 under sever drought stress condition (IR100) showed the highest PV (14.84 µmol g ^-1 FW), SOD activity (53.42 Unit mg ^-1 _protein min ^-1 ), CAT activity (72.87 nmol mg ^-1 _protein min ^-1 ), POD activity (64.17 nmol mg ^-1 _protein min ^-1 ), SSC (172.04 mg g ^-1 FW), SPC (114.16 mg g ^-1 DW) and AC (11.20 µmol g ^-1 FW ). The combined application of ET and Zn with a disirable doses, improved the most agronomic characteristics, antioxidant enzymes and non-enzymatic antioxidants under drought stress. Hence, the foliar spraying of ET20 and Zn1 could be recommendable to enhance peanut SY under similar climatic conditions.