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Immature female inflorescences are promising materials for use as explants for the tissue culture of date palm. Four types of MS media were used in this study during the four micropropagation stages-starting media (SM), maturation media (MM), multiplication media (PM) and rooting media (RM)-to micropropagate three elite date palm varieties, Amri, Magdoul and Barhy using the immature female inflorescences as explant. The highest percentage of callus induction in all the varieties studied was obtained on the SM1 (9 µM 2,4-D + 5.7 µM IAA + 10 µM NAA). Culturing on the MM1 (4.5 µM 2,4-D + 9.8 µM 2-iP + 1.5 AC) allowed us to obtain the best value in terms of callus weight. After culturing on the PM1 (4.4 µM BA + 9.8 µM 2-iP) produced the highest numbers of somatic embryos and shoots. The explants on RM2 (0.5 µM NAA + 1.25 µM IBA + 3 g AC) showed the highest root numbers and root lengths, while the highest shoot length was achieved on RM3 (0.5 µM NAA + 0.5 µM IBA + 3 g AC). The Amri variety presented the best response among the three varieties in all parameters, followed by the Magdoul and Barhy varieties. In all the stages of micropropagation, the analysis of variance revealed highly significant variations among varieties and culture media, and a significant difference in the number of roots during the rooting stage. The results also showed non-significant differences in the interaction between varieties and culture media, except for shoot length in the rooting stage. The results also reveal the broad sense heritability ranging from low to high for the measured parameters. It can be concluded that the immature female inflorescences can be used as a productive explant source for successful date palm micropropagation using the SM1, MM1, PM1 and RM2 culture media. It can also be concluded that the success of date palm micropropagation not only depends on the concentrations of growth regulators, but also on their types.

Nitric oxide (NO) is a well-accepted signaling molecule that has regulatory effects on plants under various stresses. Salinity is a major issue that adversely affects plant growth and productivity. The current study was carried out to investigate changes in the growth, biochemical parameters, and yield of wheat plants in response to NO donors, namely sodium nitroprusside (SNP) (2.5 and 5.0 mM) and arginine (10 and 20 mM), under two salinity levels (1.2 mM and 85.5 mM NaCl). Salinity stress significantly decreased the lengths and weights of plant parts (shoot, tiller, and root) and reduced the flag leaf area, photosynthetic pigments, indole acetic acid (IAA), and yield and its components. Moreover, salt stress induced a significant accumulation of some osmoprotectants (total soluble sugars (TSS) and amino acids, especially proline) and triggered the accumulation of hydrogen peroxide (H 2 O 2 ) and lipid peroxidation in wheat leaves. In contrast, arginine and SNP treatments significantly mitigated the negative impacts of salinity on growth and productivity via enhancing photosynthetic pigments, nitrate reductase, phenolic compounds, IAA, TSS, free amino acids, and proline. In addition, SNP and arginine potentially reduced oxidative damage by decreasing H 2 O 2 and lipid peroxidation through the induction of antioxidant enzymes. The individual amino acid composition of wheat grains under the interactive effect of salinity and NO sources has been scarcely documented until now. In this study, the NO sources restrained the reduction in essential amino acids (isoleucine and lysine) of wheat grains under salinity stress and further stimulated the contents of non-essential and total aromatic amino acids. Interestingly, the applied protectants recovered the decrease in arginine and serine induced by salinity stress. Thus, SNP or arginine at the levels of 5.0 and 20 mM, respectively, had a profound effect on modulating the salt stress of wheat throughout the life cycle.

A study was carried out to evaluate the effectiveness of sugar beet extract (SBE) and glycine betaine (GB) in mitigating the adverse effects of drought stress on two maize cultivars. Seeds (caryopses) of two maize cultivars, Sadaf (drought-tolerant) and Sultan (drought-sensitive) were sown in plastic pots. Plants were subjected to different (100%, 75% and 60% field capacity (FC)) water regimes. Then, different levels of SBE (3% and 4%) and GB (3.65 and 3.84 g/L) were applied as a foliar spray after 30 days of water deficit stress. Drought stress significantly decreased plant growth and yield attributes, chlorophyll pigments, while it increased relative membrane permeability (RMP), levels of osmolytes (GB and proline), malondialdehyde (MDA), total phenolics and ascorbic acid as well as the activities of superoxide dismutase (SOD) and peroxidase (POD) enzymes in both maize cultivars. Exogenous application via foliar spray with SBR or GB improved plant growth and yield attributes, chlorophyll pigments, osmolyte concentration, total phenolics, ascorbic acid and the activities of reactive oxygen species (ROS) scavenging enzymes (SOD, POD and catalase; CAT), but reduced leaf RMP and MDA concentration. The results obtained in this study exhibit the role of foliar-applied biostimulants (natural and synthetic compounds) in enhancing the growth and yield of maize cultivars by upregulating the oxidative defense system and osmoprotectant accumulation under water deficit conditions.

Myo-inositol has gained a central position in plants due to its vital role in physiology and biochemistry. This experimental work assessed the effects of salinity stress and foliar application of myo-inositol (MYO) on growth, chlorophyll content, photosynthesis, antioxidant system, osmolyte accumulation, and gene expression in quinoa ( Chenopodium quinoa L. var. Giza1). Our results show that salinity stress significantly decreased growth parameters such as plant height, fresh and dry weights of shoot and root, leaf area, number of leaves, chlorophyll content, net photosynthesis, stomatal conductance, transpiration, and Fv/Fm, with a more pronounced effect at higher NaCl concentrations. However, the exogenous application of MYO increased the growth and photosynthesis traits and alleviated the stress to a considerable extent. Salinity also significantly reduced the water potential and water use efficiency in plants under saline regime; however, exogenous application of myo-inositol coped with this issue. MYO significantly reduced the accumulation of hydrogen peroxide, superoxide, reduced lipid peroxidation, and electrolyte leakage concomitant with an increase in the membrane stability index. Exogenous application of MYO up-regulated the antioxidant enzymes' activities and the contents of ascorbate and glutathione, contributing to membrane stability and reduced oxidative damage. The damaging effects of salinity stress on quinoa were further mitigated by increased accumulation of osmolytes such as proline, glycine betaine, free amino acids, and soluble sugars in MYO-treated seedlings. The expression pattern of OSM34, NHX1, SOS1A, SOS1B, BADH, TIP2, NSY, and SDR genes increased significantly due to the application of MYO under both stressed and non-stressed conditions. Our results support the conclusion that exogenous MYO alleviates salt stress by involving antioxidants, enhancing plant growth attributes and membrane stability, and reducing oxidative damage to plants.

Bacterial blight (BB) is caused by Xanthomonas oryzae pv. oryzae and is one of the most important diseases in rice. It results in significantly reduced productivity throughout all rice-growing regions of the world. Four BB resistance genes have been reported; however, introgression of a single gene into rice has not been able to sufficiently protect rice against BB infection. Pyramiding of effective BB resistance genes (i.e., Xa genes) into background varieties is a potential approach to controlling BB infection. In this study, combinations of four BB resistance genes, Xa4 , xa5 , xa13 , and Xa21 , were pyramided into populations. The populations were derived from crossing Ciherang (a widespread Indonesian rice variety) with IRBB60 (resistance to BB). Promising recombinants from the F 6 generation were identified by scoring the phenotype against three virulent bacterial strains, C5, P6, and V, which cause widespread BB infection in most rice-growing countries. Pyramiding of genes for BB resistance in 265 recombinant introgressed lines (RILs) were confirmed through marker-assisted selection (MAS) of the F 5 and F 6 generations using gene-specific primers. Of these 265 RILs, 11, 34 and 45 lines had four, three, or two BB resistance genes, respectively. The RILs had pyramiding of two or three resistance genes, with the Xa4 resistance gene showing broad spectrum resistance against Xoo races with higher agronomic performance compared to their donor and recipients parents. The developed BB-resistant RILs have high yield potential to be further developed for cultivation or as sources of BB resistance donor material for varietal improvement in other rice lines.

Allantoin ((AT) a purine metabolite)-mediated ultraviolet C (UVC) stress mitigation has not been studied to date. Here, we reported the physicochemical mechanisms of UVC-induced stress in tomato ( Solanum lycopersicum L.) plants, including an AT-directed mitigation strategy. UVC stress reduced plant growth and photosynthetic pigments. Heatmap and principal component analysis (PCA) revealed that these toxic impacts were triggered by the greater oxidative damage and disruption of osmolyte homeostasis. However, pre-treatment of AT noticeably ameliorated the stress-induced toxicity as evident by enhanced chlorophyll, soluble protein, and soluble carbohydrate contents in AT-pretreated UVC-stressed plants relative to only stressed plants leading to the improvement of the plant growth and biomass. Moreover, AT pre-treatment enhanced endogenous AT and allantoate content, phenylalanine ammonia-lyase, non-enzymatic antioxidants, and the enzymatic antioxidants leading to reduced oxidative stress markers compared with only stressed plants, indicating the protective effect of AT against oxidative damage. Moreover, PCA displayed that the protective roles of AT strongly associate with the improved antioxidants. On the other hand, post-treatment of AT showed less efficacy in UVC stress mitigation relative to pre-treatment of AT. Overall, this finding illustrated that AT pre-treatment could be an effective way to counteract the UVC stress in tomato, and perhaps in other crop plants.

Perennial shrub-annual plant interactions play key roles in desert regions influencing the structure and dynamics of plant communities there. In the present study, carried out in northwestern Saudi Arabia, we examined the effect of Haloxylon salicornicum shrubs on their associated understory annual species across four consecutive growing seasons, along with a record of the seasonal rainfall patterns. We measured density and species richness of all the annual species in permanent quadrats located beneath individual shrubs, as well as in the spaces between shrubs. During wet growing season H. salicornicum shrubs significantly enhanced the density and species richness of sub-canopy species, whereas in the relatively dry seasons they exerted negative effects on the associated species. In all growing seasons, the presence of shrubs was associated with enhanced soil properties, including increased organic carbon content, silt + clay, and levels of nutrients (N, P and K). Shrubs improved soil moisture content beneath their canopies in the wet growing season, while in the dry seasons they had negative effects on water availability. Differences in effects of H. salicornicum on understory plants between growing seasons seem due to the temporal changes in the impact of shrubs on water availability. Our results suggest the facilitative effects of shrubs on sub-canopy annuals in arid ecosystems may switch to negative effects with increasing drought stress. We discuss the study in light of recent refinements of the well-known "stress-gradient hypothesis".