Desert-adapted Plants Research Articles

Legumes of Arizona: An Illustrated Flora and Reference

The Fabaceae is one of the most ecologically, economically, and agriculturally important plant families in the world. These plants are particularly significant in Arizona as many species are native and adapted to arid lands. Desert-adapted plants will become increasingly important as water issues of the state become more critical. Additionally, legumes are important and sometimes dominant components of the many biotic communities in Arizona. This manual meets a critical need for a reference on these plants in Arizona.

Roots of the xerophyte Panicum turgidum host a cohort of ionizing-radiation-resistant biotechnologically-valuable bacteria

Bacterial communities associated with roots of Panicum turgidum, exposed to arid conditions, were investigated with a combination of cultural and metataxonomic approaches. Traditional culture-based techniques were used and 32 isolates from the irradiated roots were identified as belonging to Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria phyla. Four actinobacterial strains were shown to be ionizing-radiation (IR)-resistant: Microbacterium sp. PT8 (4.8 kGy (kGy)), Micrococcus sp. PT11 (4.4 kGy), Kocuria rhizophila PT10 (2.9 kGy) and Promicromonospora panici PT9T (2.6 kGy), based on the D10 dose necessary for a 90% reduction in colony forming units (CFU). Concerning the investigation of microbial communities in situ, metataxonomic analyses of the diversity of IR-resistant microorganisms associated with irradiated roots revealed a marked dominance of Actinobacteria (46.6%) and Proteobacteria (31.5%) compared to Bacteroidetes (4.6%) and Firmicutes (3.2%). Gamma irradiation not only changed the structure of bacterial communities, but also affected their functional properties. Comparative analyses of metabolic profiles indicated the induction of several pathways related to adaptation to oxidative stress in irradiated roots, such as DNA repair, secondary metabolites synthesis, reactive oxygen species (ROS)-mitigating enzymes, etc. P. turgidum is emblematic of desert-adapted plants. Until now, there is no other work that has focused on the microbial profile of irradiated roots of this xerophyte.

Microhabitats associated with solar energy development alter demography of two desert annuals.

Political and economic initiatives intended to increase energy production while reducing carbon emissions are driving demand for solar energy. Consequently, desert regions are now targeted for development of large‐scale photovoltaic solar energy facilities. Where vegetation communities are left intact or restored within facilities, ground‐mounted infrastructure may have negative impacts on desert‐adapted plants because it creates novel rainfall runoff and shade conditions. We used experimental solar arrays in the Mojave Desert to test how these altered conditions affect population dynamics for a closely related pair of native annual plants: rare Eriophyllum mohavense and common E. wallacei. We estimated aboveground demographic rates (seedling emergence, survivorship, and fecundity) over 7 yr and used seed bank survival rates from a concurrent study to build matrix models of population growth in three experimental microhabitats. In drier years, shade tended to reduce survival of the common species, but increase survival of the rare species. In a wet year, runoff from panels tended to increase seed output for both species. Population growth projections from microhabitat‐specific matrix models showed stronger effects of microhabitat under wetter conditions, and relatively little effect under dry conditions (lack of rainfall was an overwhelming constraint). Performance patterns across microhabitats in the wettest year differed between rare and common species. Projected growth of E. mohavense was substantially reduced in shade, mediated by negative effects on aboveground demographic rates. Hence, the rare species were more susceptible to negative effects of panel infrastructure in wet years that are critical to seed bank replenishment. Our results suggest that altered shade and water runoff regimes associated with energy infrastructure will have differential effects on demographic transitions across annual species and drive population‐level processes that determine local abundance, resilience, and persistence.

Islands in the desert: environmental distribution modelling of endemic flora reveals the extent of Pleistocene tropical relict vegetation in southern Arabia.

Southern Arabia is a global biodiversity hotspot with a high proportion of endemic desert-adapted plants. Here we examine evidence for a Pleistocene climate refugium in the southern Central Desert of Oman, and its role in driving biogeographical patterns of endemism. Distribution data for seven narrow-range endemic plants were collected systematically across 195 quadrats, together with incidental and historic records. Important environmental variables relevant to arid coastal areas, including night-time fog and cloud cover, were developed for the study area. Environmental niche models using presence/absence data were built and tuned for each species, and spatial overlap was examined. A region of the Jiddat Al Arkad reported independent high model suitability for all species. Examination of environmental data across southern Oman indicates that the Jiddat Al Arkad displays a regionally unique climate with higher intra-annual stability, due in part to the influence of the southern monsoon. Despite this, the relative importance of environmental variables was highly differentiated among species, suggesting that characteristic variables such as coastal fog are not major cross-species predictors at this scale. The co-occurrence of a high number of endemic study species within a narrow monsoon-influenced region is indicative of a refugium with low climate change velocity. Combined with climate analysis, our findings provide strong evidence for a southern Arabian Pleistocene refugium in Oman's Central Desert. We suggest that this refugium has acted as an isolated temperate and mesic island in the desert, resulting in the evolution of these narrow-range endemic flora. Based on the composition of species, this system may represent the northernmost remnant of a continuous belt of mesic vegetation formerly ranging from Africa to Asia, with close links to the flora of East Africa. This has significant implications for future conservation of endemic plants in an arid biodiversity hotspot.

The role of the endophytic fungus, Thermomyces lanuginosus, on mitigation of heat stress to its host desert plant Cullen plicata.

Endophytic fungi associated with desert plants have a crucial role to enable these plants to tolerate abiotic stress, such as heat and drought. In this study, a thermophilic fungal endophyte was isolated from a hot desert-adapted plant, Cullen plicata Delile. The endophytic fungus was (molecularly) identified as Thermomyces lanuginosus, and inoculated plants were coded as E+ and the control as E-. This fungus had an effective growth-promoting activity on its host plant and increased the plant resistance to heat stress as well. Our findings demonstrate that thermophilic fungal endophytes can enhance drought and heat stress tolerance in desert plants by ecophysiological mechanisms and improve growth of its host plants.

Eco-physiological and biochemical characterization of Rhus tripartita (Ucria) Grande growing in Algerian Sahara under arid climate

Rhus tripartita (Ucria) Grande, is an Anacardiaceae autochthonous shrub of the Algerian Sahara. Its ecological, pastoral and therapeutics interests prompted us to carry out an eco-physiological and biochemical behavior in relation to aridity. Therefore, relative water content of shrub leaves were found on average 81.55% and the maximum of electrolyte leakage recorded was 14.29. The biochemical determination of proteins and sugars shows that leaves are a true source of protein (33.76 mg/g FM) and sugars (938.93 μg/g FM) while the proline assay gave a value of 824.40 μg/g. The quantitative study of flavonoids in the leaves gave a result of 36.53 mg/g. The analysis of photosynthetic pigments content showed respectively results of 28.1 μg/g, 31.24 μg/g, 56.47 μg/g and 11.23 μg/g for chlorophyll a, chlorophyll b, total chlorophyll and carotenoids. The total antioxidant capacity was evaluated and gave result of 95.5 mg GAE/g. Therefore, Rhus tripartita was found to accumulate high proportions of primary and secondary metabolites which showed a good adaptation to its arid environment. In conclusion, the plant can be considered as a xeromorphic plant, that is, a desert-adapted plant that is not limited by the water availability.

Trace elements concentrations in soil, desert-adapted and non-desert plants in central Iran: Spatial patterns and uncertainty analysis

The concentrations of Cd, Cr and Pb in soil samples and As, Cd, Cr and Pb in plant specimens were analyzed in an arid area in central Iran. Plants were categorized into desert-adapted (Haloxylon ammodendron, Atraphaxis spinosa and Artemisia persica) and non-desert species. It was found that the trace element (TE) accumulating potential of the desert species (Haloxylon ammodendron and Artemisia persica) with a mean value of 0.1 mg kg−1 for Cd was significantly higher than that of the majority of the non-desert species with an average of 0.05 mg kg−1. Artemisia also had a high As accumulating capability with a mean level of 0.8 mg kg−1 in comparison with an average of 0.2 mg kg−1 for most of the other plant species. The mean values of Cr and Pb in Haloxylon ammodendron and Artemisia persica were 5 and 3 mg kg−1, respectively. Among the desert-adapted plants, Atraphaxis proved to be a species with high Cr and Pb accumulating potential, as well. The geoaccumulation index and the overall pollution scores indicated that the highest environmental risk was related to Cd. Different statistical analyses were used to study the spatial patterns of soil Cd and their connections with pollution sources. The variogram was estimated using a classical approach (weighted least squares) and was compared with that of the posterior summaries that resulted from the Bayesian technique, which lay within the 95% Bayesian credible quantile intervals (BIC) of posterior parameter distributions. The prediction of cadmium values at un-sampled locations was implemented by multi-Gaussian kriging and sequential Gaussian simulation methods. The prediction maps showed that the region most contaminated by Cd was the north-eastern part of the study area, which was linked to mining activities, while agricultural influence contributed less in this respect.

Effect of Thermomyces fungal endophyte isolated from extreme hot desert-adapted plant on heat stress tolerance of cucumber

With the increasing effects of global climate change and population growth, there is a high need for new agricultural practices to maximize efficiencies and reduce the efforts needed for developing new crop varieties that can withstand various abiotic stress. Plant-microbe association to optimize plant growth and increase plant host stress tolerance may play an essential role in improving environmental sustainability and economic viability, especially in the arid land habitats. In the present study, photosynthetic responsiveness was selected to demonstrate that a theromophilic endophytic (CpE) fungus isolated from the hot desert-adapted delile (Cullen plicata) roots can mediate heat stress tolerance in cucumber plants grown in the field during the summer season in Egypt. Initially, the CpE isolate was identified using an internal transcribed spacer, revealing 92% sequence homology with Thermomyces sp. Then the cucumber seeds were treated with CpE endophyte spore and allowed to grow in a growth chamber for three weeks before transplanting into the field station from May to July. The CpE treatment eliminates the adverse effects of heat stress on cucumber plants by maintaining the maximum quantum efficiency of photosystem II, photosynthesis rate, water use efficiency and increase root length relative to untreated plants. In addition, CpE treatments induced the significant accumulation of total sugars, flavonoids, saponins, soluble proteins and antioxidant enzyme activities in comparison with untreated cucumber plants. Our finding provides novel insights into the eco-physiological mechanisms of thermophilic CpE-mediated heat stress tolerance in cucumber, which signify the prospective applications of arid land-adapted endophytes in agricultural systems.

The moderating effect of water-efficient ground cover vegetation on pedestrian thermal stress

The level of thermal stress experienced by pedestrians in an urban environment is affected by their exchange of energy with their surroundings, and the properties of ground-cover vegetation can have an important influence on this energy exchange − particularly in terms of radiation. Although vegetated surfaces have a low albedo and thus absorb a large part of the solar radiation incident upon them, they can maintain lower temperatures than typical paved surfaces because they are cooled by evapotranspiration. The purpose of this research is to examine the cooling effect of “succulent” surface cover plants that are adapted to arid climates, in comparison to plants such as grass that require substantially more irrigation. The research site, in the Negev desert of southern Israel, consists of several small test plots with different species of succulents and other plants, along with dry ground surfaces. Measurements of surface temperature and albedo provide input for comprehensive pedestrian thermal comfort modeling using the Index of Thermal Stress, assuming an open space scenario with various surface cover treatments. Water requirements of the different plant are examined through an irrigation experiment. Results indicate that although there are thermal differences between the different plant types, these differences are small when compared with non-vegetated surfaces. While the non-succulents are slightly cooler and less stress-inducing than the desert-adapted plants, their water requirements are higher, making them less efficient in terms of the ratio between cooling “benefits” and water “costs”—both of which are expressed in terms of their equivalent energy.

The San Joaquin Desert of California: Ecologically Misunderstood and Overlooked

The vegetation community of the San Joaquin Valley of California has been formally classified as a perennial grassland based largely on assumptions of past climax state. However, historical records suggest that the region might be more accurately classified as a desert. The distinction is important in determining the appropriate management strategies for this ecosystem, particularly for the many rare and endemic taxa that reside there. Abiotic and biotic factors—including low precipitation, arid soils, and desert-adapted plants and vertebrate—are consistent with conditions typical of desert areas. We examined the distributions of these factors to define the extent of the San Joaquin Desert. We conclude that the San Joaquin Desert historically encompassed 28,493 km2 including the western and southern two thirds of the San Joaquin Valley, and the Carrizo Plain and Cuyama Valley to the southwest. However, this ecosystem has been reduced by up to 59% from agricultural, industrial, and urban activities. The conservation of the unique biodiversity of this region is dependent upon this ecosystem being appropriately managed as a desert and not as a perennial or annual grassland.

ANATOMICAL FEATURES, OTHER THAN WOOD, IN SUBFAMILY OPUNTIOIDEAE (CACTACEAE)

Abstract Fifty species of Opuntioideae were examined to establish 1) the range of anatomical variation occurring in this subfamily, 2) characters these plants share with other desert-adapted plants, and 3) information about phylogenetic relationships within Cactaceae. Only three characters are universally present in stem-photosynthetic, stem-succulent plants: 1) a persistent epidermis, 2) a thickened cortex, and 3) a palisade cortex. A multiseriate hypodermis with extremely thick walls and crystals is almost universally present in Opuntioideae and Cactoideae but is not uniformly present in non-cactus succulents. Opuntioideae lack many features common in Cactoideae: they have no extremely thick cortex, no extensive system of cortical bundles, no collapsible cortex cells, and no medullary bundles. Features common to Pereskia, Cactoideae and Opuntioideae, which may be relictual in the family, are 1) a tendency to form multiple epidermis, 2) a multiseriate, thick-walled hypodermis with druses in at least one ...

286 Plant Life Form Frequency, Diversity, and Irrigation Application in Urban Residential Landscapes

Heightened awareness of ecological concerns have prompted many municipalities to promote water conservation through landscape design. In central Arizona, urban residential landscapes containing desert-adapted plant species are termed xeriscapes, while those containing temperate or tropical species and turf are termed mesoscapes. Research was conducted to ascertain landscape plant species diversity, tree, shrub, and ground cover frequency; landscape canopy area coverage; and monthly irrigation application volumes for xeric and mesic urban residential landscapes. The residential urban landscapes were located in Tempe and Phoenix, Ariz., and all were installed initially between 1985 and 1995. Although species composition of xeric and mesic landscapes was generally dissimilar, both landscape types had comparable species diversity. Mesoscapes had significantly more trees and shrubs and about 2.3 times more canopy area coverage per landscaped area than xeriscapes. Monthly irrigation application volumes per landscaped surface area were higher for xeriscapes. Even though human preference for xeric landscape plants may be ecological in principle, use of desert-adapted species in central Arizona urban residential landscape settings might not result in less landscape water use compared with mesic landscapes.

From a Limestone Ledge by John Graves, and: The Desert Smells Like Rain by Gary Paul Nabhan

280 Western American Literature tablature. The songs that are presented are relayed line-by-line, in poem-form. Gone, too, are Danny Timmons’wonderful line drawings that accompanied the previous edition. The “Poetry”section (distinct from “Songs”) is expanded with nine new authors, while the “Fiction” section offers two additional—and three new—authors. Introductory essays precede each major section, and provide biographical sketches of authors. The collection remains rich and diverse in genre, source, and time. The pieces span the evolution of native American literature, from traditional to mainstream, from the ancient (though still active) oral tradition to selections from Scott Momaday and Louise Erdrich. As Velie admonishes, these works are not “quaint relics of a forgotten people”; rather, their common bond across traditions and regional cultures is their literary quality. D. E. McIVOR Utah Stale University From a Limestone Ledge. ByJohn Graves. (Louisville, Colorado: The Audio Press, 1990. 2 cassettes, 3 hours, $15.95.) The Desert Smells Like Rain. By Gary Paul Nabhan. (Louisville, Colorado: The Audio Press, 1990. 2 cassettes, 2'Y\ hours, $15.95.) Maybe it’s something atavistic in my character, but I like a good story, read aloud. And for those of us who regret the fading of the oral tradition from our culture, The Audio Press gives reason for hope. Gary Nabhan reads from two of his works: TheDesert Smells Like Rain (1982) and Gathering the Desert (1985). He is an ethnobotanist, and his tales, set in the Sonoran Desert, are of the intricately woven relationship between the Tohono O’odham (Papago), the land, and their domesticated, desert-adapted plants. John Graves is an astute observer of the ebb and flow of life on his Northcentral Texas farm. He reads from Hardscrabble (1973, 1974), and From a Limestone Ledge (1980). The stories speak of daily concerns, from choosing land to the management of a modest herd of cattle, to fencing, and working with the occasional Mexican immigrant. These avuncular stories are ultimately about John Graves, and I like that; they take me to his porch on a cooling Texas evening. D. E. McIVOR Utah State University World Outside the Window: The Selected Essays of Kenneth Rexroth. Edited by Bradford Morrow. (New York: New Directions, 1987. 319 pages, $12.95.) World Outside the Windoiu: The SelectedEssays ofKenneth Rexroth offers a broad swath of twenty-seven essays by the San Francisco poet, Asian-verse translator ...