Arid Zone Plants Research Articles

The effects of spring versus summer heat events on two arid zone plant species under field conditions.

Heatwaves are increasingly occurring out-of-season, which may affect plants not primed for the event. Further, heat stress often coincides with water and/or nutrient stress, impairing short-term physiological function and potentially causing downstream effects on reproductive fitness. We investigated the response of water-stressed arid-zone Solanum oligacanthum and Solanum orbiculatum to spring vs summer heat stress under differing nutrient conditions. Heat stress events were imposed in open-topped chambers under in situ desert conditions. To assess short-term impacts, we measured leaf photosystem responses (Fv/Fm) and membrane stability; long-term effects were compared via biomass allocation, visible damage, flowering and fruiting. Plants generally fared more poorly following summer than spring heat stress, with the exception of Fv/Fm. Summer heat stress caused greater membrane damage, reduced growth and survival compared with spring. Nutrient availability had a strong influence on downstream effects of heat stress, including species-specific outcomes for reproductive fitness. Overall, high temperatures during spring posed a lower threat to fitness than in severe arid summer conditions of high temperature and low water availability, which were more detrimental to plants in both the short and longer term. Our study highlights the importance of considering ecologically relevant, multiple-stressor events to understand different species responses to extreme heat.

Global change impacts on arid zone ecosystems: Seedling establishment processes are threatened by temperature and water stress.

Recruitment for many arid‐zone plant species is expected to be impacted by the projected increase in soil temperature and prolonged droughts associated with global climate change. As seed dormancy is considered a strategy to avoid unfavorable conditions, understanding the mechanisms underpinning vulnerability to these factors is critical for plant recruitment in intact communities, as well as for restoration efforts in arid ecosystems. This study determined the effects of temperature and water stress on recruitment processes in six grass species in the genus Triodia R.Br. from the Australian arid zone. Experiments in controlled environments were conducted on dormant and less‐dormant seeds at constant temperatures of 25°C, 30°C, 35°C, and 40°C, under well‐watered (Ψsoil = −0.15 MPa) and water‐limited (Ψsoil = −0.35 MPa) conditions. Success at three key recruitment stages—seed germination, emergence, and survival—and final seed viability of ungerminated seeds was assessed. For all species, less‐dormant seeds germinated to higher proportions under all conditions; however, subsequent seedling emergence and survival were higher in the more dormant seed treatment. An increase in temperature (35–40°C) under water‐limited conditions caused 95%–100% recruitment failure, regardless of the dormancy state. Ungerminated seeds maintained viability in dry soil; however, when exposed to warm (30–40°C) and well‐watered conditions, loss of viability was greater from the less‐dormant seeds across all species. This work demonstrates that the transition from seed to established seedling is highly vulnerable to microclimatic constraints and represents a critical filter for plant recruitment in the arid zone. As we demonstrate temperature and water stress‐driven mortality between seeds and established seedlings, understanding how these factors influence recruitment in other arid‐zone species should be a high priority consideration for management actions to mitigate the impacts of global change on ecosystem resilience. The knowledge gained from these outcomes must be actively incorporated into restoration initiatives.

Occupancy and diet of the Indian desert fox Vulpes vulpes pusilla in a Prosopis juliflora invaded semi-arid grassland

Encroachment by woody invasive plants has been recognized as a major driver of structural change in grasslands ecosystems. The impact of invasive plant-mediated changes on mammalian species from higher trophic levels is relatively less understood. This study aims to understand the impact of woody encroachment on the ecology of a relatively understudied mesopredator, the Indian desert fox Vulpes v. pusilla in a semi-arid saline grassland ecosystem in Western India. We examined the site occupancy of the Indian desert fox at the landscape level, and den site selection at the micro-habitat scale. We also examined the diet of desert foxes during winter and summer season. We found that at the landscape level the desert fox selects more open Suaeda saline habitats over dense invasive Prosopis juliflora dominated habitats. At the scale of the den, proximity to water and vegetation cover were the main drivers of den site selection. Similar to other arid zone foxes, insects, plant materials and small mammals were the main components of the diet of Indian desert fox. Given its selection of open habitats, invasive shrub encroachment is likely to result in a loss of habitat as well as resources for this species, potentially impacting on the conservation status of this already range-restricted species in India.

Tolerancia de plantas de zonas áridas a metales pesados

En México las zonas áridas representan más de la mitad del territorio, en estos lugares existe erosión debido a la contaminación, por lo que es importante estudiar el nivel de tolerancia de las especies vegetales representativas para restaurar o reforestar. Se evaluaron seis especies de zonas áridas Agave funkiana, A. obscura, A. salmiana de la familia Asparagaceae y Opuntia cochenillifera, O. f icus-indica, Pereskia sacharosa, de la familia Cactaceae. Se propagaron in vitro para la obtención de brotes que fueron establecidos a diferentes concentraciones de cadmio (Cd2+) y plomo (Pb2+) durante la etapa de enraizamiento para determinar su tolerancia. Se utilizó el método Probit para calcular la concentración letal media (CL50) de las seis especies a las diferentes dosis. Las diferentes concentraciones de Cd y Pb, produjeron distintos efectos en las seis especies de plantas de zonas áridas evaluadas en esta investigación. A. salmiana y P. sacharosa obtuvieron una mortalidad de 55% con 0.009 mM de Cd y una mortalidad de 77% con 0.8 mM para Pb, siendo estas concentraciones las más altas. Los bioensayos ecotoxicológicos son útiles para evaluar contaminantes como los metales pesados en plantas tolerantes como A. obscura, O. cochenillifera y O. f icus-indica.

Germinación de Echinocereus pectinatus (cactácea) mediante tratamientos de escarificación a diferente concentración de ácido sulfúrico

Echinocereus pectinatus es una cactácea endémica de México, considerada como especie en peligro de extinción por su recolecta ilegal y dificultad de propagación y reproducción. Nuestro país, es uno de los que cuentan con una importante superficie en la cual la precipitación es menor de 300 mm en promedio anual, estimándose que la superficie supera el 40% del territorio Nacional. La presente investigación se realizó a partir de la conciencia ética de protección y multiplicación de especies de zonas áridas en riesgo con el propósito de proteger este material genético para continuar con la protección de la diversidad de la flora chihuahuense, teniendo como objetivo elevar el porciento de germinación de la semilla de Echinocereus pectinatus, utilizando procesos de escarificación a base de ácido sulfúrico (concentraciones del 10, 15, 20, 25, 30%). No se detectó diferencia estadística significativa entre tratamientos para la germinación de la semilla de esta especie de cactácea; sin embargo, se obtuvo información valiosa para explorar espacios en la concentración de ácido sulfúrico entre 10 y 20% en el rompimiento de la latencia, observándose una tendencia en la elevación del porcentaje de germinación en el rango de estos tratamientos referidos a la concentración de ácido sulfúrico. Se concluyó con base en los resultados y la literatura revisada en varias especies vegetales de zonas áridas, que los mejores resultados de germinación por escarificación ocurren en tratamientos menores a 20% de ácido sulfúrico.

Thysanoptera host-plant associations, with an account of species living on Tamarix, and a new species of Lissothrips (Phlaeothripidae).

Eight unrelated Thysanoptera species are known to be associated with the arid zone plant genus Tamarix [Tamaricaceae]. One new species, Lissothrips hemingi sp.n., is described from Iran based on specimens collected on branches of Tamarix. Liothrips jazykoviMoulton, described from specimens taken on Tamarix, is considered a new synonym of Liothrips reuteri (Bagnall), a widespread species on the foliage of this plant.

Isolation and Lack of Potential Mates may Threaten an Endangered Arid-Zone Acacia.

Clonality may provide reproductive assurance for many threatened plants while limiting sexual reproductive success either through energetic tradeoffs or because clones are self-incompatible. Most stands of the Australian arid-zone plant Acacia carneorum, flower annually but low seed set and an absence of sexual recruitment now suggest that this species and other, important arid-zone ecosystem engineers may have low genotypic diversity. Indeed, our recent landscape-scale genetic study revealed that stands are typically monoclonal, with genets usually separated by kilometers. An inability to set sexually produced seed or a lack of genetically diverse mates may explain almost system-wide reproductive failure. Here, using microsatellite markers, we genotyped 100 seeds from a rare fruiting stand (Middle-Camp), together with all adult plants within it and its 4 neighboring stands (up to 5 km distant). As expected, all stands surveyed were monoclonal. However, the Middle-Camp seeds were generated sexually. Comparing seed genotypes with the single Middle-Camp genotype and those of genets from neighboring and other regional stands (n = 26), revealed that 73 seeds were sired by the Middle-Camp genet. Within these Middle-Camp seeds we detected 19 genotypes in proportions consistent with self-fertilization of that genet. For the remaining 27 seeds, comprising 8 different genotypes, paternity was assigned to the nearest neighboring stands Mallee and Mallee-West, approximately 1 km distant. Ironically, given this species' vast geographic range, a small number of stands with reproductively compatible near neighbors may provide the only sources of novel genotypes.

Clonality disguises the vulnerability of a threatened arid zone Acacia.

Long‐lived, widespread plant species are expected to be genetically diverse, reflecting the interaction between large population sizes, overlapping generations, and gene flow. Such species are thought to be resilient to disturbance, but may carry an extinction debt due to reproductive failure. Genetic studies of Australian arid zone plant species suggest an unusually high frequency of asexuality, polyploidy, or both. A preliminary AFLP genetic study implied that the naturally fragmented arid zone tree, Acacia carneorum, is almost entirely dependent on asexual reproduction through suckering, and stands may have lacked genetic diversity and interconnection even prior to the onset of European pastoralism. Here we surveyed microsatellite genetic variation in 20 stands to test for variation in life histories and further assessed the conservation status of the species by comparing genetic diversity within protected stands in National Parks and disturbed range lands. Using herbarium records, we estimate that 219 stands are extant, all of which occur in the arid zone, west of the Darling River in southeastern Australia. With two exceptions, all surveyed stands comprised only one multilocus genet and at least eight were putatively polyploid. Although some stands comprise thousands of stems, our findings imply that the species as a whole may represent ~240 distinct genetic individuals, many of which are polyploid, and most are separated by >10 km of unsuitable habitat. With only 34% of stands (and therefore genets) occurring within conservation reserves, A. carneorum may be at much greater risk of extinction than inferred from on‐ground census data. Land managers should prioritize on‐ground preservation of the genotypes within existing reserves, protecting both vegetative suckers and seedlings from herbivory. Importantly, three stands are known to set viable seed and should be used to generate genetically diverse germ‐plasm for ex situ conservation, population augmentation, or translocation.

Evaluation of genetic fidelity among micropropagated plants of Salvadora persica L. using DNA-based markers

Salvadora persica L. (family Salvadoraceae) is a highly threatened medicinally and economically important arid zone plant species. With ever increasing demand, there is a pressing need for conservation and mass multiplication of this plant through biotechnological approaches. A large number of complete plantlets were obtained by direct regeneration from the nodal explants on Murashige and Skoog (MS) medium supplemented with 2.0mg/l 6-benzylaminopurine (BAP)+1.0mg/l indole-3-acetic acid (IAA) containing 30g/l sucrose and 8g/l agar at 16h photoperiod. A high frequency of in vitro rooting was obtained on half strength MS medium supplemented with 3.0mg/l indole-3-butyric acid (IBA). The micropropagated plantlets were hardened using sterilized soil and sand mixture (3:1) and successfully transferred under field conditions. The genetic stability of micropropagated clones was evaluated using random amplified polymorphic DNA (RAPD) analysis. During the study a total of 43 RAPD primers were screened, out of which 8 primers produced a total of 37 clear, distinct and reproducible amplicons. The amplified products of all the regenerated plants were monomorphic and were similar to the mother plant, thus confirming the genetic homogeneity of tissue culture raised plants. To the best of our knowledge, it is the first report on the assessment of the genetic fidelity in micropropagated plants of S. persica, which could be successfully applied as one of the safest modes for the production of true-to-type plants for the germplasm conservation.

Correlative Evaluation of the Impact of Adaptive Plant Morphology on Bioactive Accumulation Based on Micro-Morphological Studies in Andrographis serpyllifolia (Rottler ex Vahl) Wight

Does the adaptive plant morphology actually hint at its potential bioactive profile? To understand and decipher this, a micro-morphological investigation was conducted on an arid zone plant. Andrographis serpyllifolia (Rohl.ex.vahl.) Wight is a slightly bitter, acrid endemic herb with fair history of ethno-botanical use among different tribes of peninsular India. A. serpyllifolia was a highly evolved geophyte well-suited for high survivability in extremely harsh terrain. This plant was found to grow and perpetuate successfully under high-stress conditions of water deficit, high soil and atmospheric temperatures, poor nutrition and constant threat from herbivores. Under such circumstances, this plant possessed the potential to develop morphological adaptations that produce and accumulate a wide range of phytochemicals that could preserve, protect and defend its plant body. The twin objectives of this study were to investigate the micro-morphological features and their functional advantage that enabled the plant to flourish in adverse conditions and interpret by deductive reasoning, the potential phytochemical array of this plant given the observed features. Scanning electron microscope was used to explore surface morphologies of various vegetative and floral parts. Key findings of this micro-morphological study were presence of numerous diacytic stomata on both adaxial and abaxial leaf surfaces, abundant glandular sessile trichomes on abaxial leaf surfaces, reticulate pollen ornamentation with echinate sulcus outlined with smooth morus and deeply reticulate, highly pitted spermoderm or seed testa reminiscent of human brain. These three features may serve as pharmacognostic markers aiding in accurate identification and quality control of this herb.

Ecophysiological Indicators to Assess Drought Responses of Arid Zone Native Seedlings in Reconstructed Soils

AbstractRestoration of degraded arid and semi‐arid land faces the challenge of reinstating vegetation communities exposed to limited and variable rainfall events that in combination with a deficit of original topsoil may exceed thresholds for seedling development. In a series of glasshouse experiments, we evaluated variation in drought responses of (i) 21 arid zone plant species from the mining intensive Pilbara region of Western Australia in an original topsoil substrate and (ii) four selected species (Acacia inaequilatera, Acacia spondylophylla, Eucalyptus leucophloia and Triodia epactia) in three different soil substrates (topsoil, overburden material and a blend of both soil materials) that may be considered as an alternative substrate for restoration. Seedling drought responses were tested using ecophysiological indicators (e.g. stomatal conductance and leaf water potential (Ψleaf) at the time of stomatal closure, among others) during soil drying. Our results showed that plant life form and morphological traits interact with ecophysiological indicators to show that trees are significantly less tolerant to drought‐related stress than shrubs and herbs (p ≤ 0·05). When grown in overburden material seedlings experienced a decline in overall plant growth (87% in T. epactia and 62% in E. leucophloia) and ecophysiological drought tolerance. These responses are evidence of the low quality of the overburden substrate, which has a depleted nutrient content and low water retention capacity. Overall, this study highlights the sensitivity of early seedling development and the importance of facilitating seedling recruitment and survival to secure successful arid zone restoration. Copyright © 2016 John Wiley & Sons, Ltd.

Untangling a species complex of arid zone grasses (Triodia) reveals patterns congruent with co-occurring animals

The vast Australian arid zone formed over the last 15million years, and gradual aridification as well as more extreme Pliocene and Pleistocene climate shifts have impacted the evolution of its biota. Understanding the evolutionary history of groups of organisms or regional biotas such as the Australian arid biota requires clear delimitation of the units of biodiversity (taxa). Here we integrate evidence from nuclear (ETS and ITS) and chloroplast (rps16-trnK spacer) regions and morphology to clarify taxonomic boundaries in a species complex of Australian hummock grasses (Triodia) to better understand the evolution of Australian arid zone plants and to evaluate congruence in distribution patterns with co-occurring organisms. We find evidence for multiple new taxa in the T. basedowii species complex, but also incongruence between data sets and indications of hybridization that complicate delimitation. We find that the T. basedowii complex has high lineage diversity and endemism in the biologically important Pilbara region of Western Australia, consistent with the region acting as a refugium. Taxa show strong geographic structure in the Pilbara, congruent with recent work on co-occurring animals and suggesting common evolutionary drivers across the biota. Our findings confirm recognition of the Pilbara as an important centre of biodiversity in the Australian arid zone, and provide a basis for future taxonomic revision of the T. basedowii complex and more detailed study of its evolutionary history and that of arid Australia.

From the desert it came: evolution of the Australian paper daisy genus Leucochrysum (Asteraceae, Gnaphalieae)

Present patterns of diversity in the Australian flora have been shaped by increasing seasonality since the Eocene, and by pronounced aridification in the past 3 million years. Arid-zone plants are commonly hypothesised to be the products of radiations of ancestrally temperate or coastal lineages, as in the case of the everlasting paper daisy tribe Gnaphalieae (Asteraceae). However, these inferences are often based on higher-level phylogenies, whereas evolutionary processes in the Australian Gnaphalieae have rarely been studied at the species level. Here, we reconstructed the phylogeny and biogeographic history of the small, but ecologically diverse, paper daisy genus Leucochrysum, to examine recent habitat shifts and character changes, at the same time exploring the feasibility of using amplicon sequencing of low-copy nuclear gene regions to resolve phylogenetic relationships in Australian Gnaphalieae. On the balance of evidence, outgroup comparison and ancestral-area reconstruction support an ancestral range in the arid zone with subsequent diversification towards the south-east, demonstrating a complex evolutionary history with a re-colonisation of temperate areas. Low amplification success rates suggest that methods other than amplicon sequencing of currently available primers will be more promising for molecular phylogenetic work at a larger scale.

Arid awakening: new opportunities for Australian plant natural product research

The importance of plants and other natural reserves as sources for biologically important compounds, particularly for application in food and medicine, is undeniable. Herein we provide a historical context of the major scientific research programs conducted in Australia that have been aimed at discovering novel bioactive natural products from terrestrial plants. Generally speaking, the main approaches used to guide the discovery of novel bioactive compounds from natural resources have included random, ethnobotanical and chemotaxonomic strategies. Previous Australian plant natural product research campaigns appear to have lacked the use of a fourth strategy with equally high potential, namely the ecologically guided approach. In addition, many large studies have sampled plant material predominantly from tropical regions of Australia, even though arid and semi-arid zones make up 70% of mainland Australia. Therefore, plants growing in arid zone environments, which are exposed to different external stressors (e.g. low rainfall, high ultraviolet exposure) compared with tropical flora, remain an untapped reservoir of potentially novel bioactive compounds. Research of Australian arid zone plants that is ecologically guided creates a new opportunity for the discovery of novel bioactive compounds from plants (and potentially other biota) for application in health care, food and agricultural industries.

The population dynamics of some arid zone plants during 46 years of grazing on Mileura Station, Western Australia

Grazed quadrats were monitored on Mileura Station, Western Australia from 1967 to 2013 in order to study the population dynamics of the perennial plants in two of the land systems on the property. Counts of plants on four quadrats at each of 10 sites were made in 1967, 1976, 1990 and 2013, and individual plants were traced for the first three samplings. Five sites were on the Sherwood land system and five on the Belele land system. The results indicated that the populations of some species in the mulga shrubland increased steadily over the 46 years of the study whereas the populations of other species, especially the small, short-lived shrubs, fluctuated over this period. A reduction in stocking rate from 1976 to 1990 was associated with an increase in the population of perennial plants; the total numbers for the 1976 count were 1506 compared with 2102 in 1990. Mean summer rainfall increased between 1990 and 2013 and this increase may have been associated with the recruitment. Overall, the study showed that commercial stocking, although at a lower rate than that recommended by the Western Australian Department of Agriculture, was compatible with increases in the populations of the perennial components of mulga shrubland in this region.

Amorphophallus species as potential source of antimicrobial agent

Medicinal plants are the mirror image of wealthy India. Medicinal plants are the great source of various natural compounds that have important medicinal values and can be used for the well being of human welfare and for the safety of environment. Amorphophallus species related to the Arid Zone of India. Arid zone plants have specific antifungal, antibacterial and Anti- inflammatory activity because of the some specific bioactive compounds, that makes these plants adaptable to be growing in the desert environment. The present study was performed to screen the antimicrobial ability of Amorphophallus species against selected test microbes using its methanolic and petroleum ether extract. Petroleum ether extract and methanolic extract both shows appreciable antimicrobial activity against test microbes. Petroleum ether shows maximum activity against S. sonnei (10mg/disc, IZ=15, AI= 0.46) and K. pneumonia (10mg/disc, IZ= 14, AI= 0.35) and minimum activity against T. rubrum and negative against C. albicans. The result of methanolic extract activity was excellent. The activity was maximum against P. aeruginosa (5mg/disc, IZ= 20, AI= 1.42) and low against Klebsiella pneumonia.

RAPD Analysis to Study Metagenome Diversity in Soil Microbial Community of Arid Zone Plants

The study was conducted by taking six soil samples, two each for Capparis decidua (Ker), Calligonum polygonoides (Phog) collected from Bikaner while third sample, Cuminum cyminum (Cumin) was collected from Jobner. RAPD analysis was done using various decamer primers. The total bands amplified varied from 7 (UBC 153) to 13 (UBC 157). Three primers (UBC 153, 154 and 162) showed 100 % polymorphism. 46 out of 53 polymorphic allelic positions were obtained with 86.7 % polymorphism. The number of bands generated was plant and soil dependent.

Evaluation of Plant Growth Promoting Rhizobacterial Activity in Soil Samples of Arid Zone Plants

In the present investigation, soil samples of Capparis decidua L., Calligonum polygonoides L., Cuminum cyminum Gmel. were taken from different areas of Rajasthan. The bacterial isolates were evaluated for their plant growth promoting rhizobacterial (PGPR) activity, by nitrogen fixation and phosphate solubilization activity. K3, P40, C63, and C79 were the isolates that showed both activities and C63 and C79 showed very good response among all the isolates selected for each plant species. These PGPR may serve as bioinoculants to increase availability and uptake of mineral nutrients for plants and stimulate growth of plants in arid soils of Rajasthan. Rhizobacterial isolates from C. cyminum C63, C68, and C60 showed positive PGPR activity i.e., increased root and shoot length, mean wet biomass, and percent germination.

The ages and fecundity of some arid-zone plants in Western Australia

Since 1960, 22 species of individually marked, arid-zone perennial plants in the Murchison District and Gibson Desert of Western Australia have been monitored for flowering, fecundity, and survival. The age to which individual species survive was determined in terms of half-life, i.e. the time elapsed for half of the marked sample to die. The estimates ranged from 6.5 to 535 years. Phenology was recorded by observing whether the plants carried buds, flowers, fruits, or any combination of these, or were sterile. Fecundity of each species was measured by recording each year the percentage of the sample trees that carried fruit, by collecting seeds in trays placed beneath the plants and by counting the pods produced by some species. Fecundity was related to seasonal rainfall, most species responding positively to summer rainfall. The concept of mast years, as utilised in the northern hemisphere, was applied to recorded fecundities and some evidence was found that, after a year of high fecundity, the plants responded less vigorously to conditions of high rainfall than they did in the previous year of high rainfall. This suggests that, in years when fecundity is high, it diminishes the resources available within the plants to respond to heavy rainfall the following year or reduces the soil nutrients available to them.

Relationships among leaf traits of Australian arid zone plants: alternative modes of thermal protection

Despite the importance of leaf traits that protect against critically high leaf temperatures, relationships among such traits have not been investigated. Further, while some leaf trait relationships are well documented across biomes, little is known about such associations within a biome. This study investigated relationships between nine leaf traits that protect leaves against excessively high temperatures in 95 Australian arid zone species. Seven morphological traits were measured: leaf area, length, width, thickness, leaf mass per area, water content, and an inverse measure of pendulousness. Two spectral properties were measured: reflectance of visible and near-infrared radiation. Three key findings emerged: (1) leaf pendulousness increased with leaf size and leaf mass per area, the former relationship suggesting that pendulousness affords thermal protection when leaves are large; (2) leaf mass per area increased with thickness and decreased with water content, indicating alternative means for protection through increasing thermal mass; (3) spectral reflectance increased with leaf mass per area and thickness and decreased with water content. The consistent co-variation of thermal protective traits with leaf mass per area, a trait not usually associated with thermal protection, suggests that these traits fall along the leaf economics spectrum, with leaf longevity increasing through protection not only against structural damage but also against heat stress.