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Orthotrichum Hedw. s.l. and Ulota Mohr s.l. are two of the most speciose genera of the xerophytic moss family Orthotrichaceae. We reconstructed the phylogeny of these two genera using three data matrices: (i) organellar genomes and 33 taxa; (ii) six loci from three genomes and 144 taxa; and (iii) two plastid loci and 163 taxa. The present phylogeny, based on the maximum sampling of genes or taxa to date, generally confirms the new classification of Orthotrichum and Ulota, and indicated that all Ulota species, except Ulota phyllantha Brid., form a clade and three lineages comprise the cryptoporous Orthotrichum clade. We provided new morphological characters that support the present division of the two genera. Ancestral state reconstruction of stoma indicates that superficial stomata in Orthotrichum represent a plesiomorphic character and semi‐immersed stomata were derived from immersed stomata. The results also suggest that immersed stomata independently arose once in Orthotrichum, whereas semi‐immersed stomata probably arose more than once. Molecular dating analysis reveals that the occurrence of immersed stomata is probably related to arid environments during the early Oligocene to late Miocene, whereas the appearance of semi‐immersed stomata might be associated with the mesic–xeric or semiarid environments during the middle Miocene to Pliocene. Ancestral state reconstruction of habitat indicates that the saxicolous habitat is apomorphic and independently evolved multiple times in Orthotrichum and Ulota, which supports the former hypothesis. Considering morphological statistics, the development of the cryptopore in Orthotrichum could provide increased resilience to dry habitats, and might promote their habitat shift during evolution. [ABSTRACT FROM AUTHOR]

Aim: Using the extremophile genus Anabasis, which includes c. 28 succulent, xerophytic C4 species, and is widely distributed in arid regions of Northern Africa, Arabia, and Asia, we investigate biogeographical relationships between the Irano‐Turanian floristic region (ITfr) and its neighboring regions. We test whether the spread of arid and semi‐arid biomes in Eurasia coincides with the biogeography of this droughtadapted genus, and whether the ITfr acted as source area of floristic elements for adjacent regions. Location: Deserts and semi‐deserts of Northern Africa, Mediterranean, Arabia, West and Central Asia. Methods: Four cpDNA markers (rpL16 intron, atpB‐rbcL, trnQ‐rps16, and ndhF‐rpL32 spacers) were sequenced for 58 accessions representing 21 Anabasis species. Phylogenetic relationships and divergence times were inferred using maximum likelihood and a time‐calibrated Bayesian approach. To document the extant distribution of Anabasis, material from 23 herbaria was surveyed resulting in 441 well‐documented collections used for the coding of eight floristic regions. Using this coded data, ancestral range was estimated using “BioGeoBEARS” under the DEC model. Results: Anabasis originated during the Late Miocene and the ancestral range was probably widespread and disjunct between Western Mediterranean and the Irano‐ Turanian regions. Diversification started with two divergence events at the Miocene/Pliocene boundary (5.1 and 4.5 mya) leading to Asian clade I with ITfr origin which is sister to a slightly younger Asian clade II, which originated in the Western ITfr, and a Mediterranean/North African clade with an origin in the Western Mediterranean. Main conclusions: Anabasis did not follow aridification and continuously expanded its distribution area, in fact its probably wide ancestral distribution area seems to have been fragmented during the very Late Miocene and the remnant lineages then expanded into neighboring arid regions. This genus supports the role of the ITfr as source area for xerophytic elements in the Mediterranean and Central Asia. [ABSTRACT FROM AUTHOR]

In arid zones, precipitation distribution is extremely uneven, with saline-waterlogging and dry-moist cycles appearing frequently, which negatively impact on seed germination and seedling establishment. The responses of two halophytes, Suaeda physophora and Haloxylon ammodendron, and a xerophyte, Haloxylon persicum, to saline-waterlogging and dry-moist cycles were studied. The results showed that aeration increased seed germination for all species when seeds were submerged in NaCl, especially for xerophyte. Compared with S. physophora and H. ammodendron, seed germination, recovery germination, and total germination of H. persicum were much lower when seeds were submerged in 700 mM NaCl, especially for the recovery germination and total germination of nongerminated seeds when the seeds were desiccated and then transferred to distilled water. However, when the seeds were submerged in 700 mM NaCl with aeration, the seed germination, recovery germination, and total germination of nongerminated seeds transferred to distilled water increased dramatically for H. persicum. No adverse effect of desiccation was found on those values of nongerminated seeds pretreated in NaCl with or without aeration for the two halophytes. In conclusion, seeds of the two halophytes were more tolerant to waterlogging and dry-moist cycles than seeds of the xerophyte during emergence under saline conditions; these traits may be important for halophytes to survive extreme saline environments during the seed germination stage. [ABSTRACT FROM AUTHOR]

The genus Cucurbita (Cucurbitaceae) includes five species that were domesticated independently in the Americas, giving rise to an immense diversity of squashes, pumpkins, and gourds. To gain an improved understanding of the evolution of Cucurbita and its domesticated taxa, we used four chloroplast loci to estimate the phylogeny of 23 taxa that represent the broad-level diversity within Cucurbita. Our results provide a strongly supported framework hypothesis for the phylogeny of the genus, robustly confirming the basal position of the C. digitata group of xerophytic perennials and the monophyly of a large group of mesophytic annuals that represent most of the known diversity in the genus, both wild and domesticated. The chloroplast evidence provides strong support for a novel grouping of the mesophytic annual C. ficifolia (known only from cultivation) with the xerophytic perennials C. foetidissima and C. pedatifolia. This study also provides the first DNA-based evidence in support of the isozyme-based hypothesis that C. pepo subsp. ovifera var. ovifera (represented by most ornamental gourds and several squashes) was domesticated from the wild taxon C. pepo subsp. ovifera var. ozarkana. This lends support to the hypothesis that var. ovifera was domesticated in the eastern United States and that this region served as one of about 10 independent centers of origin of human agriculture. Although the level of bootstrap support for this and certain other peripheral relationships in Cucurbita is low, definitive resolution of these issues is within reach, as next-generation sequencing should soon deliver entire organelle genome sequences from a comprehensive sampling of the genus. [ABSTRACT FROM AUTHOR]

1. Germination and seedling performance may set the limits for plant distributions, particularly in stressful habitats. Stressful conditions at these early stages may be avoided by opportunistic germination and growth, or may be tolerated. Many epiphytic plants are frequently exposed to severe drought. Adult epiphytes endure such dry periods in various ways, but little is known about strategies employed during germination and early life. 2. Epiphyte seedlings could show either opportunistic fast growth to quickly attain the benefits of being larger or inherently slow growth and early drought tolerance. Here we address the question: which of these strategies characterizes the early life stages of the epiphytic bromeliad Tillandsia flexuosa, a specie s typical for dry tropical habitats? 3. We studied growth and drought tolerance of germinating seeds, of the emerging seedlings and of 2-month-old seedlings under controlled conditions. Additionally, we studied drought hardening in 6-month-old seedlings. 4. Germination of T. flexuosa was reduced by intermittent dry periods. However, compared to the congeneric T. fasciculata, which typically occurs in wetter habitats, the depression of germination by drought was small. Seedling growth was fastest at intermediate moisture levels: both prolonged drought and continuous moisture depressed growth. Prolonged drought had a less negative effect on drought-hardened seedlings than on previously well-watered seedlings. After a 3-week drought treatment the previously well-watered seedlings had lost their growth advantage entirely. Had drought continued, they would have probably been starved, indicated by the low level of their non-structural carbohydrate pool. 5. Tillandsia flexuosa employs a stress-tolerance strategy both during germination and during the seedling stage. In its epiphytic habitat this strategy is clearly adaptive, considering the predictable briefness of moisture availability throughout the year and the low competition pressure that allows the very slow growth typically seen in adults and seedlings. These conditions characterize not only the dry-forest habitat of T. flexuosa, but all exposed epiphytic growing sites, so we expect this early stress-tolerance to be common among epiphytes in general. Still, a lower stress tolerance in species from wetter habitats may at least partly explain why T. flexuosa shares its dry-forest habitat with so few other vascular epiphytes. [ABSTRACT FROM AUTHOR]

• The effects of salinity and nitrogen (N) on growth and the role of NO3− in osmotic adjustment in the leaf-succulent euhalophyte Suaeda physophora and the stem-succulent xerophyte Haloxylon persicum were evaluated. • Seedlings were exposed to 1 or 300 mm NaCl in 0.05, 1 or 10 mm NO3−-N treatments for 24 d. • At 10 mm NO3−, 300 mm NaCl had no adverse effect on the concentration of NO3−, the content of organic N, and the estimated contribution of NO3− to osmotic potential in leaves of S. physophora, but markedly reduced these in stems of H. persicum. At 300 mm NaCl, more NO3− but less Cl− and Na+ were involved in osmotic adjustment in leaves of S. physophora compared with that in stems of H. persicum. The contribution of NO3− to osmotic potential was much higher in S. physophora, but lower in H. persicum, than that of amino acids at 300 mm NaCl. • The nutritional and osmotic roles of NO3−-N seem to be more important in the euhalophyte S. physophora than in the xerophyte H. persicum under saline conditions. These characteristics may determine the natural distributions of the two species in saline or arid environments. [ABSTRACT FROM AUTHOR]

The effect of arbuscular mycorrhizal fungi (AMF) on six plant species that frequently grow in areas of Mediterranean climate in south-east Spain was studied. In semi-arid soils, the most abundant AMP was Glomus aggregatum Schenek arid Smith, followed by Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe. The vascular plant species studied were Dittrichia viscosa (L.) W. Greuter (Asteraceae); Dactylis glomerata L., Piplatherum miliaceum (L.) Cosson, and Stipa tenacissima L. (Poaceae); Retama sphaerocarpa (L.) Hoiss., and Ulex parviflorus Pourret (Fabaceae). Legumes were studied with single and dual symbiosis (Rhizobium and AMF). In a greenhouse experiment, inoculated plants developed better than noninoculated controls, as shown by dry weight and tissue N and P content. Plants inoculated with G. aggregatum grew better than plants inoculated with G. mosseae. For this reason G. aggregatum was chosen for a held experiment, in which this AM fungus increased shoot dry mass, shoot length, and percent survival after transplantation. The effects of soil microorganisms on development, survival and fertility of native plants, their influence on the effects of the erosion, and their importance in plant repopulation programmes are discussed. [ABSTRACT FROM AUTHOR]