Iranian Journal of Plant Physiology
Volume:12 Issue: 2, Winter 2022

Water shortage or drought stress is an environmental factor that strongly affects crops ‎productivity in various regions of the world. Sowing date as a factor affecting the growth ‎and yield of oilseed crops can alleviate drought stress occurring in reproductive stage. To ‎assess this, agronomic and physiological response of five canola genotypes (L1030, L1204, ‎L1110, L1114 and Okapi) to drought stress were evaluated at two early and late sowing ‎dates (7th and 27th October, respectively) as a two-year field experiment. Results showed ‎that drought stress significantly reduced the seed yield and yield components of all ‎genotypes at both sowing dates, which was a consequence of damage to photosynthetic ‎pigments, reduction of relative water content. However, early sowing was able to alleviate ‎drought stress effect; as seed yield of different genotypes at early sowing were 38-47% ‎higher than late sowing. Moreover, the measured oil content was not influenced by drought ‎stress and sowing date, so the highest oil content at both sowing dates were recorded in ‎L1204 genotypes. Finally, the results showed that sowing of suitable genotype in the proper ‎date could be an appropriate approach to canola sowing in semi-arid areas.‎

Heat stress has become one of the major constraints in maize production worldwide. The current research was planned to define the heat stress-related characteristics of indigenous and exotic maize hybrids based on morpho-physiological and grain quality traits. The research was conducted at Maize & Millets Research Institute (MMRI), Yusafwala, Sahiwal during spring 2019. Hybrids were sown under two heat regimes: (i) optimal sowing and (ii) sowing under heat stress (late sowing). Hybrids differed significantly (P<0.05) in grain yield and related traits under both conditions. Correlation analysis showed a positive correlation of grain yield with net photosynthetic rate (r = 0.393*), days to 50% anthesis (r = 0.437*) and days to 50% silking (r = 0.429*), and a negative association with ear leaf angle (r = −0.420*) under heat stress. Cluster analysis categorized maize hybrids into three clusters based on their mean performance under optimal and heat stress conditions. It further showed that indigenous hybrids (cluster 3), especially KSC-9663, YH-5519, YH-5482, YH-1898, and YH-5507, were more productive and heat tolerant than exotic hybrids i.e., MV-633, MV-600-4, Maxima, SHG-43, and MV-600-2 (cluster 1). Principal component analysis (PCA) and biplot graphs showed that the first five principal components contributed 72% of the total variability among genotypes and that the main sources of variation were days to 50% anthesis and silking, plant height, percentage of protein, and oil contents, stomatal conductance, and net photosynthetic rate.

In order to investigate the effect of foliar application of iron (Fe), zinc (Zn) and boron (B) on grain yield and some physiological characteristics of soybeans under water stress, two separate experiments were conducted in a randomized complete block design with eight treatments in three replications in Aleshtar, Lorestan, during 2013-2014 and 2014-2015. In one experiment, irrigation was performed after 50 mm of evaporation and in the second experiment, irrigation was performed after 100 mm of evaporation from the Class A evaporation pan. Experimental treatments included: spraying of pure water, Zn, Fe, B, Zn + Fe, Zn + B, Fe + B and Zn + Fe + B. The results of variance analysis showed that the effects of irrigation and foliar application were significant on grain yield, proline content, soluble sugars, chlorophyll a, chlorophyll b, PWC and anthocyanin. The water stress resulted to increase proline content under water stress condition compared with normal irrigation. Water stress also was led to decrease grain yield (30%). The most grain yield was related to normal irrigation treatment (2070.5 kg.ha-1) and foliar application of Zn + Fe + B (2200.1 kg.ha-1).

The current study investigated the efficiency of soil supplementation with Silicon Oxide (SiO2) nanoparticle product (nSi; 20-30 nm; 0, 0.75, and 1.5 gKg-1) or Potassium silicate (BSi; K2SiO3 as a bulk counterpart) to improve strawberry protection against salinity (NaCl of 2.5 gkg-1). The BSi or nSi utilization not only increased fresh root mass (mean= 23 %) but also mitigated the inhibitory effects of salinity. The salinity, BSi, or nSi treatments made changes in secondary metabolites confirmed by the differential HPLC chromatogram. The soil supplementation with BSi or nSi induced activity of phenylalanine ammonia-lyase. Likewise, the BSi or nSi treatments enhanced concentrations of phenylpropanoid derivatives, including salicylic acid, ascorbic acid, quercetin, apigenin, caffeic acid, catechin, and chlorogenic acid.The individual salinity treatment caused a severe H2O2 accumulation by two folds. However, the BSi or nSi supplementation alleviated the salinity-associated risk of H2O2 accumulation. Salt stress caused a drastic increase in lipid peroxidation levels. However, BSi or nSi applications partially relieved the salinity toxicity on membrane integrity. With a similar trend, the BSi or nSi utilization improved the nutritional status of K+, Na+, and Ca+2 in both leaves and roots. Exposure to BSi, nSi, and/or salinity also enhanced proline concentrations. The BSi or nSi treatments mitigated the salinity-mediated down-regulations in photosynthesis performance. Our findings showed that silicon supplements increased salicylic acid (a signaling compound), ascorbate, and quercetin (two vital antioxidants) as fundamental mechanisms.

Soil salinization is one of the threats that affect the germination, growth, and production of many crops. The present study has evaluated to what degree Azolla piñnata extracts can improve the salt tolerance of Lentil (Lens culinaris, Giza 9) seeds. Germination percentage, salt tolerance, plumule and radicle lengths and seedling vigor index were gradually reduced at 150 and 200 mM NaCl salt stress. While the catalase and ascorbic oxidase activity was gradually inhibited at the two levels of NaCl salt-stress, peroxidase and polyphenol oxidase activity was significantly enhanced. Total soluble sugar in salt-stressed Lentils along with α-amylase activity was also lowered. The phytohormones auxins, gibberellic acids, and zeatin were highly decreased at 150 mM NaCl, while the abscisic acid level was not affected. On the other side, H2O2, lipid peroxidation, and proline levels were drastically enhanced at 150 and 200 mM NaCl salt stress. Salt-stressed Lentilsʹ extracts (2, 4, 6 and 8 mg ml-1) had a high H2O2 scavenging activity percentage compared to unstressed ones. Fresh or boiled extract of Azolla piñnata alleviated all negative effects of 150 mM NaCl salt-stress on Lentils by enhancing the activity of the antioxidant enzymes, H2O2 scavenging capacity, α-amylase activity; and elevating soluble sugars, proline and phytohormones content (particularly gibberellic acid). Germination was finally recovered by Azolla extracts which may be considered as a piece of evidence to support the application of Azolla piñnata extracts as a biostimulant to improve germination and early growth of many species under salinity.

To evaluate the protein response of barley cultivars under salinity stress, leaf samples were prepared at 0, 3, 6, 9, 12 and 15 days after the tillering stage. Following two-dimensional electrophoresis, 153 and 141 protein spots were identified in tolerant (Afzal) and sensitive cultivars (Macouei), respectively. In total, 21 and 17 spots with significant induction factor (IF) were revealed in Afzal and Macouei, respectively. Most common proteins between two cultivars were involved in the removal of antioxidants (five proteins), and for each protein group including heat shock, proton transfer, Calvin cycle and photosynthesis optical reaction proteins, a protein was detected. Also, 12 protein spots were exclusively present in tolerant cultivar (Afzal), most of them involved in the elimination of antioxidants, and eight protein spots were found exclusively in sensitive cultivar (Macouei), which was also largely involved in the removal of antioxidants. Lower expression of these proteins in the susceptible cultivar compared to tolerant cultivar resulted in decreased homeostasis in susceptible cultivar under salinity stress. Also, for most proteins, the highest and lowest protein expression levels occurred in tolerant and susceptible cultivars at 12 and 9 days after initiation of salinity stress.

In a study to select sensitive and tolerant soybean lines to drought-stress and selection of superior genotypes, 80 soybean lines obtained from crosses of Karbin×Fora cultivars immediately with control (cultivar L.17) in crop rotation 2016-2017 In the Lurestan-Saraab research farm sit, they were evaluated in the form of a Lattice design 9×9 with two replications. The results of the analysis of variance showed significant differences between the control line and other lines there was a significant difference between the blocks for different traits. According to the results of stepwise regression and PCA traits were grouped into four components, accounting for about 62% of the total variation. The evaluation of grain yield potential and accurate evaluation with PCA of traits led to the selection of lines superior lines in the experiment. The results of this study showed that plant height, number of pods per plant, number of seeds per pod, and 100- seed weight can be used as criteria for selection to improve seed yield in drought-stress condition soybeans.

Drought stress during growth and seed maturation is one of the most major environmental constraints, which influences seed grain filling and consequential germination and early growth stages of plants. In this study, the impact of foliar application of micronutrients (control, Zn, Fe, Zn + Fe, nano-Zn, nano-Fe, nano-Zn + nano-Fe) on quinoa at 2 reproductive stages (50% and 100% of flowering stage) were evaluated under 2 levels of drought stress (50% and 85% of depletion of soil moisture content). The results revealed that germination traits including germination percentage, and seed technological parameters such as germination value and germination energy, antioxidant enzymes activities and chlorophyll (Chl) content were significantly affected by foliar application of micronutrients, time of micronutrient spraying and drought stress level. The correlation results showed that 1000- grain weight had a positive and significant relationship with grain filling period, physiological maturity, germination percentage (GP) and germination speed (GS). The drought stress also increased the antioxidant enzymes activities of catalase (CAT) and peroxidase (POD) in all nutrients treatments. Drought stress at seed formation stage had a significant effect on seed filling and its weight and could decrease seed germination rate. It was concluded that application of nano-Zn + nano-Fe in 50% flowering stage could promote the germination performance, seedling growth and the antioxidant capacity under drought conditions stress