Drought priming reduces Calligonum mongolicum sensitivity to recurrent droughts via coordinated regulation of osmolytes, antioxidants, and hormones.

Pre-exposure of plants to abiotic stressors may induce stress memory and improve tolerance to subsequent stresses. Here, 3-month-old Calligonum mongolicum seedlings were exposed to drought (60 days) with (primed) or without (unprimed) early drought exposure of 50 days, to determine whether this enhances seedling resistance and investigate possible underlying mechanisms. Compared to unprimed, primed seedlings had higher biomass, shoot relative water content (15% and 22%), chlorophyll a, chlorophyll b, and carotenoids. They also had more superoxide anions (O2 -• ) and H2 O2 scavenging mechanisms through higher activity of SOD, CAT, APX, and dehydroascorbate reductase in assimilating shoots and roots, resulting in less ROS and oxidative stress damage. Plants also had higher ABA and JA but lower SA, likely reflecting an adaptive response to subsequent stress. Primed seedlings accumulated more IAA and brassinosteroids, which may account for their better growth. Accumulation of glycine betaine, pro, and total amino acids in assimilating shoots and roots of primed seedlings led to reduced osmotic stress. Drivers of responses of non-primed and primed seedlings to drought varied. Responses of primed seedlings were primarily characterized by more photosynthetic pigments, increased oxidative scavenging of O2 -• and H2 O2 , more phytohormones and osmolytes. Early drought priming of drought stress memory in C. mongolicum seedlings may provide a useful management approach to improve seedling establishment in vegetation restoration programs.

Climate-resilient crops: Lessons from xerophytes.

Developing climate-resilient crops is critical for future food security and sustainable agriculture under current climate scenarios. Of specific importance are drought and soil salinity. Tolerance traits to these stresses are highly complex, and the progress in improving crop tolerance is too slow to cope with the growing demand in food production unless a major paradigm shift in crop breeding occurs. In this work, we combined bioinformatics and physiological approaches to compare some of the key traits that may differentiate between xerophytes (naturally drought-tolerant plants) and mesophytes (to which the majority of the crops belong). We show that both xerophytes and salt-tolerant mesophytes have a much larger number of copies in key gene families conferring some of the key traits related to plant osmotic adjustment, abscisic acid (ABA) sensing and signalling, and stomata development. We show that drought and salt-tolerant species have (i) higher reliance on Na for osmotic adjustment via more diversified and efficient operation of Na+ /H+ tonoplast exchangers (NHXs) and vacuolar H+ - pyrophosphatase (VPPases); (ii) fewer and faster stomata; (iii) intrinsically lower ABA content; (iv) altered structure of pyrabactin resistance/pyrabactin resistance-like (PYR/PYL) ABA receptors; and (v) higher number of gene copies for protein phosphatase 2C (PP2C) and sucrose non-fermenting 1 (SNF1)-related protein kinase 2/open stomata 1 (SnRK2/OST1) ABA signalling components. We also show that the past trends in crop breeding for Na+ exclusion to improve salinity stress tolerance are counterproductive and compromise their drought tolerance. Incorporating these genetic insights into breeding practices could pave the way for more drought-tolerant and salt-resistant crops, securing agricultural yields in an era of climate unpredictability.

Phosphorous Supplementation Alleviates Drought-Induced Physio-Biochemical Damages in Calligonum mongolicum.

Calligonum mongolicum is a phreatophyte playing an important role in sand dune fixation, but little is known about its responses to drought and P fertilization. In the present study, we performed a pot experiment to investigate the effects of P fertilization under drought or well-watered conditions on multiple morpho-physio-biochemical attributes of C. mongolicum seedlings. Drought stress leads to a higher production of hydrogen peroxide (H2O2) and malondialdehyde (MDA), leading to impaired growth and metabolism. However, C. mongolicum exhibited effective drought tolerance strategies, including a higher accumulation of soluble sugars, starch, soluble protein, proline, and significantly higheractivities of peroxidase (POD) and catalase (CAT) enzymes. P fertilization increased the productivity of drought-stressed seedlings by increasing their growth, assimilative shoots relative water content, photosynthetic pigments, osmolytes accumulation, mineral nutrition, N assimilation, and reduced lipid peroxidation. Our findings suggest the presence of soil high P depletion and C. mongolicum high P requirements during the initial growth stage. Thus, P can be utilized as a fertilizer to enhance the growth and productivity of Calligonum vegetation and to reduce the fragility of the hyper-arid desert of Taklamakan in the context of future climate change.

Alhagi sparsifolia acclimatizes to saline stress by regulating its osmotic, antioxidant, and nitrogen assimilation potential.

BACKGROUND: Alhagi sparsifolia (Camelthorn) is a leguminous shrub species that dominates the Taklimakan desert's salty, hyperarid, and infertile landscapes in northwest China. Although this plant can colonize and spread in very saline soils, how it adapts to saline stress in the seedling stage remains unclear so a pot-based experiment was carried out to evaluate the effects of four different saline stress levels (0, 50, 150, and 300 mM) on the morphological and physio-biochemical responses in A. sparsifolia seedlings. RESULTS: Our results revealed that N-fixing A. sparsifolia has a variety of physio-biochemical anti-saline stress acclimations, including osmotic adjustments, enzymatic mechanisms, and the allocation of metabolic resources. Shoot-root growth and chlorophyll pigments significantly decreased under intermediate and high saline stress. Additionally, increasing levels of saline stress significantly increased Na+ but decreased K+ concentrations in roots and leaves, resulting in a decreased K+/Na+ ratio and leaves accumulated more Na + and K + ions than roots, highlighting their ability to increase cellular osmolarity, favouring water fluxes from soil to leaves. Salt-induced higher lipid peroxidation significantly triggered antioxidant enzymes, both for mass-scavenging (catalase) and cytosolic fine-regulation (superoxide dismutase and peroxidase) of H2O2. Nitrate reductase and glutamine synthetase/glutamate synthase also increased at low and intermediate saline stress levels but decreased under higher stress levels. Soluble proteins and proline rose at all salt levels, whereas soluble sugars increased only at low and medium stress. The results show that when under low-to-intermediate saline stress, seedlings invest more energy in osmotic adjustments but shift their investment towards antioxidant defense mechanisms under high levels of saline stress. CONCLUSIONS: Overall, our results suggest that A. sparsifolia seedlings tolerate low, intermediate, and high salt stress by promoting high antioxidant mechanisms, osmolytes accumulations, and the maintenance of mineral N assimilation. However, a gradual decline in growth with increasing salt levels could be attributed to the diversion of energy from growth to maintain salinity homeostasis and anti-stress oxidative mechanisms.

Genetic variation and molecular characterization of Zygophyllum coccineum L. ecotypes of the iron mining area of El-Wahat El-Bahariya in Egypt.

Remediation and mitigation processes can recover the ecosystems affected by mining operations. Zygophyllum coccineum L. is a native indigenous xerophyte that grows in Egypt's Western Desert, particularly around the iron mining ore deposits, and accumulates high rates of potentially toxic elements (PTEs) in its succulent leaves. The present study evaluated the genetic variation and molecular responses of Z. coccineum to heavy metal stressful conditions in three sites. Results revealed that Z. coccineum bioaccumulation capacity was greater than unity and varied amongst the three locations. In response to heavy metal toxicity, Z. coccineum plants boosted their antioxidative enzymes activity and glutathione levels as a tolerance strategy. Anatomically, a compact epidermis, a thick spongy mesophyll with water storage cells, and a thicker vascular system were observed. Protein electrophoretic analysis yielded 20 fragments with a polymorphism rate of 85%. The antioxidant genes (CAT: catalase, POD: peroxidase and GST: polyphenol oxidase) showed greater levels of expression. In addition, DNA-based molecular genetic diversity analyses using Start Codon Targeted (SCoT) and Inter Simple Sequence Repeat (ISSR) markers yielded 54 amplified fragments (i.e. 24 monomorphic and 30 polymorphic), with 12 unique fragments and a polymorphism rate of 55.5%. The greatest PIC values were recorded for SCoT-6 (0.36) and for both of the 14 A and 44 B ISSR primers (0.25). Diversity index (DI) of all SCoT and ISSR amplified primers was 0.23. The present findings reveal the distinct heavy metal's adaption attributes of Z. coccineum, indicating its improved survival in severely arid mining environments.

Salinity effects on water potential and the normalized difference vegetation index in four species of a saline semi-arid ecosystem.

This study was carried out during January 2020-December 2020 in a semi-desert ecosystem in southern Sonora, Mexico, to determine the annual and daily variations in water potential and the normalized difference vegetation index (NDVI) of Bursera fagaroides Engl., Monogr. Phan., Parkinsonia aculeata L., Sp. Pl.; Prosopis laevigata (Humb. & Bonpl. ex Willd.), and Atriplex canescens (Pursh) Nutt. Soil electrical conductivity, cation content, and physical characteristics were determined at two depths, and water potential (ψ) was measured in roots, stems, and leaves. The daily leaf ψ was measured every 15 days each month to determine the duration of stress (hours) and the stress intensity (SI). The electrical conductivity determinations classified the soil in the experimental area as strongly saline. A significant difference was noted in electrical conductivity between soil depths. The four studied species showed significant gradients of ψ in their organs. In this soil, all four species remained in a stressed condition for approximately 11 h per day. The mean SI was 27%, and B. fagaroides Engl., Monogr. Phan. showed the lowest value. The four species showed increased NDVI values during the rainy months, with P. laevigata (Humb. & Bonpl. ex Willd.) and Parkinsonia aculeata L., Sp. Pl. showing the highest values. The capacity for ψ decrease under saline conditions identified A. canescens (Pursh) Nutt., B. fagaroides Engl., Monogr. Phan. and P. aculeata L., Sp. Pl. as practical and feasible alternatives for establishment in saline soils in southern Sonora for purposes of soil recovery and reforestation.

Polyphenolic extracts from the xerophyte Rhamnus lycioides as a radiation biodosimeter.

The majority of dosimeters currently in use are synthetic and very expensive. Therefore, the study of the dosimetric characteristics of polyphenolic extracts of xerophytes is useful because drought stress causes an increase in the production of these cheap and natural compounds containing benzene rings. Here, the polyphenolic compounds were extracted from Rhamnus lycioides which was collected from Bou-Hedma National Park in Tunisia and identified using liquid chromatography-mass spectrometry (LC-MS). We investigated the impact of cobalt-60 (60Co) irradiation (0-30 kilogray (kGy)) on the color parameters of polyphenolic extracts of R. lycioides using the Konica Minolta CR 300 portable colorimeter and UV-Visible spectroscopy. The structural and morphological characteristics of the irradiated extracts were assessed using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). Overall, our results suggest that exposure to ionizing radiation (IR) of the polyphenolic components of the xerophyte R. lycioides has produced significant dose-dependent changes in their optical and morphological properties. Thus, these extracts can be valorized as biodosimeters in the dose range from 5 to 25 kGy.

Impact of Combined Heat and Drought Stress on the Potential Growth Responses of the Desert Grass Artemisia sieberi alba: Relation to Biochemical and Molecular Adaptation.

Artemisia sieberi alba is one of the important plants frequently encountered by the combined effect of drought and heat stress. In the present study, we investigated the individual and combined effect of drought and heat stress on growth, photosynthesis, oxidative damage, and gene expression in A. sieberi alba. Drought and heat stress triggered oxidative damage by increasing the accumulation of hydrogen peroxide, and therefore electrolyte leakage. The accumulation of secondary metabolites, such as phenol and flavonoids, and proline, mannitol, inositol, and sorbitol, was increased due to drought and heat stress exposure. Photosynthetic attributes including chlorophyll synthesis, stomatal conductance, transpiration rate, photosynthetic efficiency, and chlorophyll fluorescence parameters were drastically reduced due to drought and heat stress exposure. Relative water content declined significantly in stressed plants, which was evident by the reduced leaf water potential and the water use efficiency, therefore, affecting the overall growth performance. Relative expression of aquaporin (AQP), dehydrin (DHN1), late embryogenesis abundant (LEA), osmotin (OSM-34), and heat shock proteins (HSP70) were significantly higher in stressed plants. Drought triggered the expression of AQP, DHN1, LEA, and OSM-34 more than heat, which improved the HSP70 transcript levels. A. sieberi alba responded to drought and heat stress by initiating key physio-biochemical and molecular responses, which were distinct in plants exposed to a combination of drought and heat stress.

Leaf Anatomy of Xylopia aromatica (Lam. ) Mart. (Annonaceae) occurring in a rocky savannah in the Brazilian Amazonian / Anatomia foliar de Xylopia aromatica (Lam. ) Mart. (Annonaceae) ocorrente em uma savana rochosa na Amazônia Brasileira

Savannas of the Amazon Region of Mato Grosso State have an unique ecological identity due to the complexity of the Cerrado-Amazon transition region, their geographical isolation and the physical-chemical properties of the soil. This study aimed to characterize the leaf anatomy of Xylopia aromatica, and to identify potential adaptive traits to the xeric environment. We collected adult leaves from X. aromatica from a Amazonian savannah located in the Nova Canãa do Norte city, Mato Grosso. The leaves were fixed and stored in 70% ethanol. Cross sections were obtained by free hand with the aid of a razor blade, stained with astra blue and basic fuchsin, and mounted on histological slides. Charactersconsidered adaptive: thick cuticle, epidermal cells with thickened walls, the presence of silica in theepidermis, trichomes, hypostomatic leaves, stomata on the same level as the other epidermal cells, presenceof hypodermis, and dorsiventral mesophyll with palisade parenchyma occupying more than 50%. Theanatomical characters presented are of great importance for the establishment and development of X.aromatica in xeric environments. They contribute to the protection of the leaves from many biotic andabiotic factors to which they are subjected, thus ensuring the species survival in the savannic environment.

A região de savana amazônica do Estado do Mato Grosso possui identidade ecológica própria, explicada pela complexa região de transição Cerrado-Amazônia, pelo isolamento geográfico e pelas propriedades físico-químicas do solo. O objetivo deste estudo foi caracterizar a anatomia foliar de Xylopiaaromatica (Lam.) Mart, identificando possíveis características adaptativas ao ambiente xerófilo. Foram coletadas folhas adultas de X. aromatica em savana amazônica, localizado no município de Nova Canaã do Norte - Mato Grosso. As folhas foram fixadas em FAA50 e armazenadas em etanol a 70%. Os cortes transversais foram obtidos a mão livre com auxílio de lâmina de barbear, corados com azul de Astra e fucsina básica e montados em lâminas histológicas. Caracteres aqui considerados adaptativos: cutículaespessa, células epidérmicas com paredes espessadas, presença de sílica na epiderme, tricomas, folhashipoestomáticas, estômatos no mesmo nível das demais células epidérmicas, presença de hipoderme, mesofilo dorsiventral com parênquima paliçádico ocupando mais de 50% e lacunoso bem compacto. Os caracteres anatômicos aqui apresentados são de grande importância para as espécies desenvolverem-se em ambientes xerófilos, demonstrando contribuição para a proteção das folhas a diversos fatores bióticos e abióticos aos quais esta se sujeita, garantindo a sobrevivência das espécies no ambiente savânico.

Diversity of bacteria nesting the plant cover of north Sinai deserts, Egypt.

North Sinai deserts were surveyed for the predominant plant cover and for the culturable bacteria nesting their roots and shoots. Among 43 plant species reported, 13 are perennial (e.g. Fagonia spp., Pancratium spp.) and 30 annuals (e.g. Bromus spp., Erodium spp.). Eleven species possessed rhizo-sheath, e.g. Cyperus capitatus, Panicum turgidum and Trisetaria koelerioides. Microbiological analyses demonstrated: the great diversity and richness of associated culturable bacteria, in particular nitrogen-fixing bacteria (diazotrophs); the majority of bacterial residents were of true and/or putative diazotrophic nature; the bacterial populations followed an increasing density gradient towards the root surfaces; sizeable populations were able to reside inside the root (endorhizosphere) and shoot (endophyllosphere) tissues. Three hundred bacterial isolates were secured from studied spheres. The majority of nitrogen-fixing bacilli isolates belonged to Bacillus megaterium, Bacillus pumilus, Bacillus polymexa, Bacillus macerans, Bacillus circulans and Bacillus licheniformis. The family Enterobacteriaceae represented by Enterobacter agglomerans, Enterobacter sackazakii, Enterobacter cloacae, Serratia adorifera, Serratia liquefaciens and Klebsiella oxytoca. The non-Enterobacteriaceae population was rich in Pantoae spp., Agrobacterium rdiobacter, Pseudomonas vesicularis, Pseudomonas putida, Stenotrophomonas maltophilia, Ochrobactrum anthropi, Sphingomonas paucimobilis and Chrysemonas luteola. Gluconacetobacter diazotrophicus were reported inside root and shoot tissues of a number of tested plants. The dense bacterial populations reported speak well to the very possible significant role played by the endophytic bacterial populations in the survival, in respect of nutrition and health, of existing plants. Such groups of diazotrophs are good candidates, as bio-preparates, to support the growth of future field crops grown in deserts of north Sinai and irrigated by the water of El-Salam canal.