Xerophytic Species Research Articles

The Influence of Water Deficit on Dehydrin Content in Callus Culture Cells of Scots Pine

Under a water deficit, the protective proteins known as dehydrins (DHNs) prevent nonspecific interactions in protein and membrane structures and their damage, in addition to playing an antioxidant role. The DHNs of a widespread xerophytic species Scots pine (Pinus sylvestris L.) have been poorly studied, and their role in resistance to water deficits has not been revealed. In this paper, we have expanded the list of DHNs that accumulate in the cells of Scots pine under the conditions of water deficits and revealed their relationship with the effects of water deficits. In this investigation, callus cultures of branches and buds of Scots pine were used. A weak water deficit was created by adding polyethylene glycol to the culture medium. Under the conditions of a water deficit, the activity of catalase and peroxidase enzymes increased in the callus cultures. A moderate decrease in the total water content was correlated with a decrease in the growth rate of the callus cultures, as well as with an increase in the activity of lipid peroxidation. The accumulation of Mr 72, 38, and 27 kDa DHNs occurred in the callus cultures of buds, and the accumulation of Mr 72 and 27 kDa DHNs positively correlated with the lipid peroxidation activity. An increase in the content of DHNs was observed in cultures that differed in origin, growth indicators, and biochemical parameters, indicating the universality of this reaction. Thus, previously undescribed DHNs were identified, the accumulation of which is caused by water deficiency and is associated with manifestations of oxidative stress in the kidney cells of Scots pine.

Effect of Drought and Rehydration on Physiological Characteristics of Agriophyllum squarrosum (L.) Moq. in Different Habitats.

Agriophyllum squarrosum (L.) Moq. is a highly prevalent xerophytic species found throughout northern China. It is suitable for cultivation in semi-arid sandy environments and may establish roots in arid desert locations. This species plays a pioneering and exploratory role in the colonization of desert plants. In this study, we selected A. squarrosum from the Urat desert steppe (UD) and Horqin sandy land (HS) to explore their adaptation mechanisms to drought and rehydration environments by using the pot weighing control method to simulate an arid environment. The findings showed that the control (watering to 60-65% of field capacity) exceeded its required amount and the leaves turned yellow. The chlorophyll content was lower than those under moderate and severe drought, and rehydration caused a decrease. However, the contents of malondialdehyde, soluble sugar, and proline in the drought treatment were higher than those in the control. Under moderate and severe drought, the chlorophyll content and the quantum efficiency of photosystem II (Fv/Fm) of A. squarrosum from UD were higher than those from HS. During drought and rehydration processes, the proline content was relatively lower, while the activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) and the content of soluble sugar and soluble protein were higher. However, antioxidant enzymes and osmoregulators from UD were higher than those from HS. The results suggest that the stronger ability of A. squarrosum to endure drought environments in UD is due to the high level of antioxidant enzymes and osmoregulators, which are conducive to relieving cell membrane damage when subjected to drought and rehydration.

Transcriptome and metabolome analysis of the developmental changes in Cynanchum thesioides anther

Cynanchum thesioides, a xerophytic species utilized both as a medicinal herb and a food source, plays a significant role in arid and desert ecosystem management. Its inflorescence is an umbellate cyme, each carrying nearly a thousand flowers; however, its fruiting rate remains remarkably low. The normal development of the anther is a necessary prerequisite for plants to produce seeds. However, our understanding of the anther development process in Cynanchum thesioides remains limited. To better understand the pollen development process in Cynanchum thesioides, the stages of pollen development were determined through paraffin sectioning, and observations were made on the distribution characteristics of polysaccharides and lipid droplets in the pollen development of Cynanchum thesioides using Periodic Acid-Schiff stain (PAS) and 0.5% Sudan Black B tissue staining. Concurrently, the gene expression patterns and metabolite profiles were delineated across various developmental stages of Cynanchum thesioides anthers (T1: microspore stage, T2: tetrad stage, T3: mononuclear stage, and T4: maturation stage). The findings revealed that Cynanchum thesioides pollen is in an aggregate form. Polysaccharides gradually accumulate during maturation and lipid droplets form a surrounding membrane, thereby preventing pollen dispersion. Furthermore, transcriptomic and metabolomic analyses across distinct developmental phases uncovered a plethora of differentially expressed genes and metabolites associated with the flavonoid biosynthesis pathway. Flavonoid levels exhibited dynamic changes concurrent with anther development, aligning with the gene regulatory patterns of the corresponding biosynthetic pathways. The study identified 63 differentially accumulated flavonoid compounds and 21 differentially expressed genes associated with flavonoid biosynthesis. Weighted gene co-expression network analysis revealed six MYB and ten bHLH transcription factors as key candidates involved in flavonoid biosynthesis, with CtbHLH (Cluster-6587.1050) and CtMYB (Cluster-6587.31743) specifically regulating structural genes within the pathway. These findings underscore the pivotal role of flavonoid biosynthesis in anther development of Cynanchum thesioides. In conclusion, this research offers a comprehensive insight into the anther development process in Cynanchum thesioides.

Phytogeographic Considerations on the Flora of Mt. Abu

The Aravallis intersect the State of Rajasthan in a southwest-northeast direction. Mt. Abu on the Aravallis is the highest point in the wide gap between the Himalayas and the Nilgiris, and thus has phytogeographlc significance. The flora of Mt. Abu has been compared with that of other hilly regions of India, and also with the flora of adjacent regions of the dry zones. It is observed that : i. the flora of Mt. Abu has some representation of mountain element belonging to subtropical and temperate regions of India. This element comprises three groups of plants, namely, (a) those occurring in all or most hilly regions of India, such as in Himalayas, Parasnath, Pachmarhi, Western Ghats, Nilgiris, etc. (26 species); (b) plants found in the Himalayas or moist places of northern India, whose southern limit is the Mt. Abu (19 species); and (c) plants found in the Ghats and hills of Deccan Peninsula and whose northern limit of distribution is Mt. Abu 38 species).ii. there are only a few plants of alpine regions in this flora;iii. large number of plants are of wide general distribution;iv. biotic factors are resulting in increase of xerophytic species on this hill.A study ofthe world distribution of the plants of Mt. Abu shows that:i. out of 469 species, 267 are tropical;ii. 80 species are eastern, southeastern, Asian and Australian;iii, 46 species are African-Arabian; andiv. 22 species are American. The American plants are mostly weeds of cultivation.

Shared xerophytic genes and their re-use in local adaptation to aridity in the desert plant Gymnocarpos przewalskii.

In order to thrive and survive, plant species need to combine stability in the long term and rapid response to environmental challenges in the short term. The former would be reflected by parallel or convergent adaptation across species, and the latter by pronounced local adaptation among populations of the same species. In the present study, we generated a high-quality genome and re-sequenced 177 individuals for Gymnocarpos przewalskii, an important desert plant species from North-West China, to detect local adaptation. We first focus on ancient adaptation to aridity at the molecular level by comparing the genomic data of 15 species that vary in their ability to withstand aridity. We found that a total of 118 genes were shared across xerophytic species but absent from non-xerophytic species. Of the 65 found in G. przewalskii, 63 were under purifying selection and two under positive selection. We then focused on local adaptation. Up to 20% of the G. przewalskii genome showed signatures of local adaptation to aridity during population divergence. Thirteen of the selected shared xerophytic genes were reused in local adaptation after population differentiation. Hence, only about 20% of the genes shared and specific to xerophytic species and associated with adaptation to aridity were later recruited for local adaptation in G. przewalskii.

Comparative effects of drought stress on three olive cultivars focusing on older leaves

Drought is one of the main abiotic stresses to which plants are exposed during their growth and development under both natural and agricultural conditions. Water shortage can seriously affect also xerophytic species such as olive (Olea europaea L.), despite the numerous anatomical, morphological, and physiological adaptations to drought developed over time. Until now, the olive physiological responses to drought stress have been studied mainly on young leaves, i.e. on leaves formed after or during water stress, while very few studies have been conducted taking into consideration leaves already existing before stress (older leaves). In this work, in order to investigate the effect of drought on 1-year-old leaves (old leaves), young plants of three Italian olive cultivars, namely ‘Degli’, ‘Leccino’, and ‘Maurino’, were subjected to moderate water stress (30 days irrigated with 10 % of the pot capacity, T1); subsequently, the same plants were exposed at severe water stress (30 days, without water supplying, T2). The results indicate that the stress tolerance of cultivars can be due to several favorable morpho-anatomical traits, such as higher percentage of palisade tissue (about 50 %) and uniform size of starch grains pre and post stress event. ‘Maurino’ stood out for its ability to cope with the imposed drought condition, maintaining an acceptable water status all over the experiment, and sustaining vegetative growth. Moreover, this olive cultivar showed a stability in the size of starch inclusions, all over the experiment. On the contrary, ‘Degli’ and ‘Leccino’ showed several negative changes under drought conditions, i.e. less growth of main branches, smaller starch grains size, marked reduction of photosynthetic activity, and reduction of leaf succulence, showing a less adaptive behaviour to water stress. Our work provides a more complete insight on olive older leaves response to drought.

Shifting patterns in fine root distribution of four xerophytic species across soil structural gradients and years of growth.

Fine root (diameter < 2 mm) distribution influences the potential for resource acquisition in soil profiles, which defines how plants interact with local soil environments; however, a deep understanding of how fine root vertical distribution varies with soil structural variations and across growth years is lacking. We subjected four xerophytic species native to an arid valley of China, Artemisia vestita, Bauhinia brachycarpa, Sophora davidii, and Cotinus szechuanensis, to increasing rock fragment content (RFC) treatments (0%, 25%, 50%, and 75%, v v-1) in an arid environment and measured fine root vertical profiles over 4 years of growth. Fine root depth and biomass of woody species increased with increasing RFC, but the extent of increase declined with growth years. Increasing RFC also increased the degree of interannual decreases in fine root diameter. The limited supply of soil resources in coarse soils explained the increases in rooting depth and variations in the pattern of fine root profiles across RFC. Fine root depth and biomass of the non-woody species (A. vestita) in soil profiles decreased with the increase in RFC and growth years, showing an opposite pattern from the other three woody species. Within woody species, the annual increase in fine root biomass varied with RFC, which led to large interannual differences in the patterns of fine root profiles. Younger or non-woody plants were more susceptible to soil environmental changes than the older or woody plants. These results reveal the limitations of dry and rocky environments on the growth of different plants, with woody and non-woody plants adjusting their root vertical distribution through opposite pathways to cope with resource constraints, which has management implications for degraded agroforest ecosystems.

A trade-off between leaf hydraulic efficiency and safety across three xerophytic species in response to increased rock fragment content.

Limited information is available on the variation of plant leaf hydraulic traits in relation to soil rock fragment content (RFC), particularly for xerophytes native to rocky mountain areas. In this study, we conducted a field experiment with four gradients of RFC (0, 25, 50 and 75% ν ν-1) on three different xerophytic species (Sophora davidii, Cotinus szechuanensis and Bauhinia brachycarpa). We measured predawn and midday leaf water potential (Ψleaf), leaf hydraulic conductance (Kleaf), Ψleaf induced 50% loss of Kleaf (P50), pressure-volume curve traits and leaf structure. A consistent response of hydraulic traits to increased RFC was observed in three species. Kleaf showed a decrease, whereas P50 and turgor loss point (Ψtlp) became increasingly negative with increasing RFC. Thus, a clear trade-off between hydraulic efficiency and safety was observed in the xerophytic species. In all three species, the reduction in Kleaf was associated with an increase in leaf mass per area. In S. davidii, alterations in Kleaf and P50 were driven by leaf vein density (VLA) and Ψtlp. In C. szechuanensis, Ψtlp and VLA drove the changes in Kleaf and P50, respectively. In B. brachycarpa, changes in P50 were driven by VLA, whereas changes in both Kleaf and P50 were simultaneously influenced by Ψtlp. Our findings suggest that adaptation to increased rockiness necessarily implies a trade-off between leaf hydraulic efficiency and safety in xerophytic species. Additionally, the trade-off between leaf hydraulic efficiency and safety among xerophytic species is likely to result from processes occurring in the xylem and the outside-xylem hydraulic pathways. These findings contribute to a better understanding of the survival strategies and mechanisms of xerophytes in rocky soils, and provide a theoretical basis for the persistence of xerophytic species in areas with stony substrates.

Herbarium specimens reveal herbivory patterns across the genus Cucurbita.

Quantifying how closely related plant species differ in susceptibility to insect herbivory is important for understanding the variation in evolutionary pressures on plant functional traits. However, empirically measuring in situ variation in herbivory spanning the geographic range of a plant-insect complex is logistically difficult. Recently, new methods have been developed using herbarium specimens to investigate patterns in plant-insect symbioses across large geographic scales. Such investigations provide insights into how accelerated anthropogenic changes may impact plant-insect interactions that are of ecological or agricultural importance. Here, we analyze 274 pressed herbarium samples to investigate variation in herbivory damage in 13 different species of the economically important plant genus Cucurbita (Cucurbitaceae). This collection is composed of specimens of wild, undomesticated Cucurbita that were collected from across their native range, and Cucurbita cultivars collected from both within their native range and from locations where they have been introduced for agriculture in temperate North America. Herbivory is common on individuals of all Cucurbita species collected throughout their geographic ranges. However, estimates of herbivory varied considerably among individuals, with mesophytic species accruing more insect damage than xerophytic species, and wild specimens having more herbivory than specimens collected from human-managed habitats. Our study suggests that long-term evolutionary changes in habitat from xeric to mesic climates and wild to human-managed habitats may mediate the levels of herbivory pressure from coevolved herbivores. Future investigations into the potential factors that contribute to herbivory may inform the management of domesticated crop plants and their insect herbivores.

ANALISIS OF PHITODIVERSITY ACCORDING TO THE STATE OF VEGETATION PF THE PETROPAVLOVSK ESTUARY LANSCAPE RESERVE AND ITS SURROUNDINGS

The Petropavlovsk estuary landscape reserve and its surroundings are subject to significant anthropogenic influence as a result of human activity. That is why the analysis of phytodiversity is important in order to get an idea of the level of transformation of the territory of the reserve. In the course of the work, an ecomorphological analysis of flora was carried out and anthropogenic influence on phytocenoses was revealed. A list of plants with bio-ecological certification, which were discovered during research, was compiled. Three points were chosen for research. During the work, 16 descriptions were made at these points, with different projective cover by vegetation twice during the growing season. The flora is characterized by a small variety of species – 94 higher vascular plants belonging to 33 families. Astracaea, Poacaea, and Rosacaea are among the main families with the greatest abundance of species. Hemicryptophytes predominate among climate morphs, and species that are partially light-demanding among ecomorphs. Biomorphs are characterized by the dominance of polycarps (perennial plants). Hygromesophyte and xerophyte species predominate in the hygrospectrum of the flora. . Species with medium moisture conditions make up 16%. The share of xerophytes in conditions of moderate moisture is 7%. Species that show wide tolerance to moisture conditions make up 2%. Among trophomorphs, mesotrophic species completely dominate. The coenomorphic structure is mainly represented by typical types of bows. In all descriptions there is a ruderal fraction, as well as species that partially or facultatively belong to this group. Due to the obvious anthropogenic influence (fouling which is a consequence of recreational and economic activities plowing, livestock grazing, there are signs of technogenic load), plant associations are poorly developed. The total fraction of adventitious species is 29%, of which 14% of species form a stable fraction in the investigated phytocenoses. There are two species, that are considered to be quarantined. Tree and shrub vegetation is very poorly developed and makes up less than 5% of the entire flora and is in a state of degression. The research area needs further observations of the state of transformational changes in vegetation that are occurring at this stage.

Mechanistic insights derived from re-establishment of desiccation tolerance in germinating xerophytic seeds: Caragana korshinskii as an example.

Germplasm conservation strongly depends on the desiccation tolerance (DT) of seeds. Xerophytic seeds have strong desiccation resistance, which makes them excellent models to study DT. Although some experimental strategies have been applied previously, most methods are difficult to apply to xerophytic seeds. In this review, we attempted to synthesize current strategies for the study of seed DT and provide an in-depth look at Caragana korshinskii as an example. First, we analyze congenital advantages of xerophytes in the study of seed DT. Second, we summarize several strategies used to study DT and illustrate a suitable strategy for xerophytic species. Then, based on our previous studies work with C. korshinskii, a feasible technical strategy for DT re-establishment is provided and we provide illustrate some special molecular mechanisms seen in xerophytic seeds. Finally, several steps to unveil the DT mechanism of xerophytic seeds are suggested, and three scientific questions that the field should consider are listed. We hope to optimize and utilize this strategy for more xerophytic species to more systematically decipher the physiological and molecular processes of seed DT and provide more candidate genes for molecular breeding.

Fatty-Acid-Rich Agave angustifolia Fraction Shows Antiarthritic and Immunomodulatory Effect.

Agave angustifolia is a xerophytic species widely used in Mexico as an ingredient in sweet food and fermented beverages; it is also used in traditional medicine to treat wound pain and rheumatic damage, and as a remedy for psoriasis. Among the various A. angustifolia extracts and extract fractions that have been evaluated for their anti-inflammatory effects, the acetonic extract (AaAc) and its acetonic (F-Ac) and methanolic (F-MeOH) fractions were the most active in a xylene-induced ear edema model in mice, when orally administered. Four fractions resulting from chemically resolving F-Ac (F1-F4) were locally applied to mice with phorbol 12-myristate 13-acetate (TPA)-induced ear inflammation; F1 inhibited inflammation by 70% and was further evaluated in a carrageenan-induced mono-arthritis model. When administered at doses of 12.5, 25, and 50 mg/kg, F1 reduced articular edema and the spleen index. In addition, it modulated spleen and joint cytokine levels and decreased pain. According to a GC-MS analysis, the main components of F1 are fatty-acid derivatives: palmitic acid methyl ester, palmitic acid ethyl ester, octadecenoic acid methyl ester, linoleic acid ethyl ester, and oleic acid ethyl ester.

Two shades of grey: effect of temperature on seed germination of the escaping ornamental species Lychnis coronaria and Stachys byzantina

This paper describes germination and cytological variability in two popular ornamental and potentially invasive species, lamb’s ear Stachys byzantina and rose campion Lychnis coronaria. Both xerophytic species have the potential to invade natural habitats across Europe and create viable naturalised populations, with subsequent impacts on native vegetation. To assess the species’ invasiveness, seeds were collected from naturalised populations and germination was recorded under different temperature regimes. Flow cytometry, used to record cytological variability, indicated that all populations of both species were cytologically homogeneous. Germination success, an important means of distribution factor in both species, was significantly influenced by temperature, with final germination of L. coronaria being extremely high at temperatures > 15/10 °C (98.5%) and extremely low at temperatures < 10/5 °C (2.9%). The final germination in S. byzantina is the highest at 22/15 °C (55.6% germinated seeds), reduced to 40.3% at 15/10 °C and to 0.3% at temperatures lower than 10/5 °C. No significant differences in final germination were observed between escaping and non-escaping populations, although there were some differences between particular populations. Our results indicate germination temperature limits of two species whose non-native areas include Central Europe. The observed germination allows for successful generative reproduction of both species over their non-native ranges, suggesting that these species are likely to become invasive species of European grasslands soon.

Phylogenetic relationships and evolutionary trends in Tillandsia subgenus Diaphoranthema and xerophytic species of subgenus Phytarrhiza (Bromeliaceae: Tillandsioideae)

Abstract Tillandsia subgenera Diaphoranthema and Phytarrhiza s.s. are closely related epiphytic and epilithic plants adapted to xeric habitats in the Americas. Several studies suggested that subgenus Diaphoranthema and the xerophytic species of subgenus Phytarrhiza should not be segregated into different subgenera. In recent phylogenetic analyses of Tillandsioideae, subgenus Phytarrhiza s.l. is revealed as highly polyphyletic, showing a xerophytic lineage closely related to subgenus Diaphoranthema. Moreover, the evolution of neotenic traits, a selfing breeding system and polyembryony have yet to be fully investigated in a phylogenetic context. Infrageneric classifications and phylogenetic relationships were inferred using the plastid matK-trnK and nuclear ETS markers and morphology. Phylogenetic analyses of individual and combined molecular data sets were performed under parsimony and Bayesian inference. Our results confirm subgenus Diaphoranthema as monophyletic if three xeric species of subgenus Phytarrhiza are included. In subgenus Diaphoranthema, aggregates Loliacea and Rectangula were recovered as monophyletic, whereas Myosura was paraphyletic and Caliginosa, Capillaris and Recurvata were polyphyletic. Alternative groupings and morphological trends are discussed. Analysis of morphological characters associated with heterochrony indicates that neoteny may not be the only paedomorphic process in the evolution of this group. Furthermore, paedomorphosis would occur in some vegetative structures, inflorescences and flowers, whereas some fruit and seed traits could be modified by peramorphosis.

Rock fragment content in soils shift root foraging behavior in xerophytic species

Root traits associated with resource foraging, including fine-root branching intensity, root hair, and mycorrhiza, may change in soils that vary in rock fragment content (RFC), while how these traits covary at the level of individual root branching order is largely unknown. We subjected two xerophytic species, Artemisia vestita (subshrub) and Bauhinia brachycarpa (shrub), to increasing RFC gradients (0%, 25%, 50%, and 75%, v v− 1) in an arid environment and measured fine-root traits related to resource foraging. Root hair density and mycorrhizal colonization of both species decreased with increasing root order, but increased in third- or fourth-order roots at high RFCs (50% or 75%) compared to low RFCs. The two species tend to produce more root hairs than mycorrhizas under the high RFCs. For both species, root hair density and mycorrhizal colonization intensity were negatively correlated with root length and root diameter across root order and RFCs. Rockiness reduced root branching intensity in both species comparing with rock-free soil. At the same level of RFC, A. vestita had thicker roots and lower branching intensity than B. brachycarpa and tended to produce more root hairs. Our results suggest the high RFC soil conditions stimulated greater foraging functions in higher root orders. We found evidence for a greater investment in root hairs and mycorrhizal symbioses as opposed to building an extensive root system in rocky soils. The two species studied, A. vestita and B. brachycarpa, took different approaches to foraging in the rocky soil through distinctive trait syndromes of fine-root components.

Reconstruction of early Paleogene landscapes and climate in the Jianghan Basin, central China: Evidence from evaporites and palynology

The early Paleogene environment and climate of East Asia are poorly understood. To improve knowledge, we investigated the palynological record of well ZK0303 in the southwest Jianghan Basin, Hubei Province (central China). The well lithology comprises three intervals whose lithofacies represent the deposits of a saline lake: anhydrite/silty mudstone, halite/mudstone, and dolomite/siltstone. Based on a study of 37 palynological samples, three assemblages were recognized. Assemblage A, which correlates with Paleocene, is dominated by Ephedripites and contains a high proportion of thermophilic and xerophytic taxa. Assemblage B, which correlates with the early Eocene, is dominated by Taxodiaceaepollenites and hygrophilous taxa while the proportion of xerophytes is generally low. Assemblage C, probably early Eocene too, is dominated by Ephedripites and contains higher numbers of xerophytic species while hygrophilous species decrease to nearly half of their earlier abundances. These palynological data show that the early Paleogene climate of the Jianghan Basin experienced a transition from hot and arid to warm and humid conditions, with the latter period interrupted by short arid intervals. Afterwards, hot-arid conditions prevailed again. The reconstructed desert shrub and mountain forest vegetation suggests that the regional Paleocene landscape resulted from basin and range tectonics. Under the influence of a hot and arid climate controlled by global circulation patterns and rain-shadow effects, desert landscape and evaporites were formed in central China during the early Paleogene, whilst humid climate and forest vegetation prevailed in central China under the influence of the Paleocene-Eocene Thermal Maximum (PETM).

The Cactaceae family in the Santa Maria river basin (Rio Grande do Sul, Brazil)

We present a paper dealing, with the family Cactaceae in the Santa Maria River Basin, which were studied by field surveys (2014–2016) and analysis of relevant literature. For each genus, species richness in the study area, general distribution, detailed, maps concerning the study area, and original pictures are provided. The species were assessed according to the IUCN categories and criteria. A key for the identification of the genera in Santa Maria River Basin was proposed. A description of the main found phytophysiognomies (field, saxicola, forest, and wetland), in which the cacti grow, were also given using Walking Method. Twenty-nine Cactaceae taxa were discovered, belonging to the following genera: Parodia (13 taxa, including a nomenclatural change, i.e. P. ritteriana comb. nov. (≡ Notocactus ritterianus), Frailea (7), Gymnocalycium (2), Wigginsia (3), Echinopsis (1), Cereus (1), and Opuntia (1), and Lepismium (1). Five species have a restricted distribution inside area in Santa Maria River Basin. The floristic diversity found in the study area is related to the edaphic and climatic conditions provided by the stony springs in the Santa Maria River Basin, which constitute a favorable microclimate of intense luminosity, heat and humidity for xerophytic species to develop in open areas.

Comparative growth, peroxidase activity and 2-D proteome analyses of halophytic and xerophytic species of Haloxylon under NaCl stress

Comparative growth, peroxidase activity and 2-D proteome analyses of halophytic and xerophytic species of Haloxylon under NaCl stress

Inferring the genetic responses to acute drought stress across an ecological gradient

BackgroundHow do xerophytic species thrive in environments that experience extreme annual drought? Although critical to the survival of many species, the genetic responses to drought stress in many non-model organisms has yet to be explored. We investigated this question in Mentzelia section Bartonia (Loasaceae), which occurs throughout western North America, including arid lands. To better understand the genetic responses to drought stress among species that occur in different habitats, the gene expression levels of three species from Mentzelia were compared across a precipitation gradient. Two de novo reference transcriptomes were generated and annotated. Leaf and root tissues were collected from control and drought shocked plants and compared to one another for differential expression. A target-gene approach was also implemented to better understand how drought-related genes from model and crop species function in non-model systems.ResultsWhen comparing the drought-shock treatment plants to their respective control plants, we identified 165 differentially expressed clusters across all three species. Differentially expressed genes including those associated with water movement, photosynthesis, and delayed senescence. The transcriptome profiling approach was coupled with a target genes approach that measured expression of 90 genes associated with drought tolerance in model organisms. Comparing differentially expressed genes with a ≥ 2 log-fold value between species and tissue types showed significant differences in drought response. In pairwise comparisons, species that occurred in drier environments differentially expressed greater genes in leaves when drought shocked than those from wetter environments, but expression in the roots mostly produced opposite results.ConclusionsArid-adapted species mount greater genetic responses compared to the mesophytic species, which has likely evolved in response to consistent annual drought exposure across generations. Drought responses also depended on organ type. Xerophytes, for example, mounted a larger response in leaves to downregulate photosynthesis and senescence, while mobilizing carbon and regulating water in the roots. The complexity of drought responses in Mentzelia suggest that whole organism responses need to be considered when studying drought and, in particular, the physiological mechanisms in which plants regulate water, carbon, cell death, metabolism, and secondary metabolites.

Do xerophytic and mesophytic perennial grasses differ in soil resource capture and allocation? A field 15N experiment

AbstractIn rangelands, pattern and processes below‐ground are important for a complete understanding of their ecology. Recent studies in grass‐dominated communities in Europe, North America and South America indicate that root systems of several species may overlap their root systems. This may indicate that, in these communities, resource acquisition and allocation strategies could play a relevant role in community assemblage. Resources absorption and allocation may be related to ecological strategies relevant in an arid steppe. Here, we explore if coexisting xerophytic and mesophytic perennial grasses differ in resource absorption and allocation to below‐ and above‐ground portions. We conducted a field labelling experiment to trace 15N (nitrogen) to compare acquisition and relative below‐ and above‐ground nitrogen allocation among four perennial grass species. We worked with two mesophytic (fast‐growing) and two xerophytic (slow‐growing) species. Our hypothesis was that mesophytic species will allocate greater proportions of N and produce a higher amount of biomass than xerophytic species. The four species showed similar 15N concentration, which changed over time in roots, while it remained constant in leaves. On average, all species presented 0.9% 15N atom excess in roots and 1.1% in green leaves. Mesophytic species showed higher reproductive over total tiller ratio than xerophytic species. Bromus pictus reached 60% while Poa ligularis only 20%. In xerophytic species (Pappostipa speciosa and Pappostipa humilis), this ratio was close to 0%. Despite their differences in growth rates, these mesophytic and xerophytic grass species do not differ in the estimated nitrogen acquisition. Nevertheless, there are ecological trade‐offs between allocating resources to above‐ground leaf biomass and reproductive tillers which could be related to species organisation in the community.