Regeneration and Genetic Transformation of Arabidopsis Pumila: An Ephemeral Plant Suitable for Investigating the Mechanisms for Adaptation to Desert Environments

Arabidopsis pumila is a type of cruciferous ephemeral plant, which in China mainly grows in the desert environments of northern Xinjiang. A. pumila not only has a short growth duration, but also has high photosynthetic efficiency, seed yield, salt tolerance, and drought resistance. It is an ideal species for the study of environmental adaptations in ephemeral plants. We induced callus tissue formation on the roots and hypocotyls of 8-day-old seedlings, and on the leaves and petioles of 4-week-old seedlings, and obtained multiple adventitious shoots on these tissues grown on Murashige and Skoog induction medium supplemented with 0.5 mg/L 6-Benzylaminopurine and 0.1 mg/L α-Naphthalene acetic acid. Young roots, hypocotyls, leaves, and petioles could all induce calluses, but the induction rate was highest on young roots. In addition, the leaves and petioles of 4-week-old seedlings were used as explants, the Δ1-pyrroline-5-carboxylic acid synthase gene 1 of A. pumila controlled by 35S promoter of cauliflower mosaic virus was used as target gene, and hygromycin B was used as screening antibiotic to explore Agrobacterium tumefaciens GV3101 mediated transformation. The results showed that the callus induction rate of petiole explants was the highest when they were treated with Agrobacterium suspension (OD600 = 0.6) for 10 min and thenco-cultured in dark for 2 d. The qRT-PCR results showed that the ApP5CS1.1 gene was overexpressed in the transgenic plants. These protocols provide working research methods for exploring the cellular level adaptative mechanisms of this species to desert environments.

Population Dynamics and Life History Response to Precipitation Changes for a Desert Ephemeral Plant With Biseasonal Germination

The changing availability of water resources and frequent extreme drought events in the context of global change will have a profound impact on desert vegetation, especially on herbaceous populations such as ephemerals. Erodium oxyrrhynchum is the dominant species in the Gurbantunggut Desert. It can germinate both in spring and autumn, which is important for herbaceous layer coverage and productivity. Therefore, we tracked and recorded the survival and reproduction of the E. oxyrrhynchum population under different precipitation treatments and established a population matrix model, monitored the allometry and leaf traits of the plants, and compared the performance of spring-germinating and autumn-germinating plants. Our results showed that: (1) The population dynamics were significantly affected by precipitation changes; (2) drought reduced the survival rate of the plants and accelerated the completion of their life history; (3) precipitation had a significant effect on seed production and growth rate, but not on plant height and allometry; (4) biomass, leaf area, specific leaf area, and 100-grain weight of E. oxyrrhynchum also responded to changes in precipitation; and (5) autumn-germinated plants had higher productivity, whereas spring-germinated plants exhibited higher reproductive efficiency, indicating that they had difference life history strategies. In conclusion, our results suggested that, although frequent or prolonged drought can significantly inhibit population growth, species with biseasonal germination are likely to be less affected.

Starmera foglemanii sp. nov. and Starmera ilhagrandensis sp. nov., two novel yeast species isolated from ephemeral plant substrates

Four isolates of two novel ascosporogenous species belonging to the clade Starmera were obtained from cactus tissues and rotting wood in Brazil. Results of analyses of the sequences of the ITS and D1/D2 domains of the large subunit rRNA gene indicated that the two isolates of the cactophilic species are related to Starmera caribaea and Starmera pilosocereana, yeasts that are associated with cacti and require an organic source of sulfur for growth. We propose the novel species Starmera foglemanii sp. nov. (CBS 16113T; MycoBank number: MB 834400) to accommodate these isolates. The other two isolates are phylogenetically related to Candida dendrica, Candida laemsonensis and Candida berthetii, also in the Starmera clade. The novel species name Starmera ilhagrandensis sp. nov. (CBS 16316T; MycoBank number: MB 834402) is proposed for this species.

Mucilage inhibits germination of desert ephemeral Nepeta micrantha seed under moderate osmotic stress and promotes recovery after release of this stress

Mucilage is considered to play an important role in the survival of seeds in harsh desert environments. Nepeta micrantha is an ephemeral plant of the Gurbantungut Desert, China. The outer surface of N. micrantha nutlets contains a layer of mucilage. We hypothesised that mucilage improves germination during and after osmotic stress. Germination of both intact and demucilaged nutlets under different polyethylene glycol (PEG)-simulated drought stress was tested at the optimal light and temperature conditions. Germination of intact and demucilaged nutlets decreased with an increase in PEG concentration. However, there were no significant differences in germination between intact and demucilaged nutlets at the same PEG concentration, except at 15% PEG. Recovery percentage and final germination of intact nutlets were considerably higher than that of demucilaged nutlets after treatment with 15% PEG. These findings demonstrate that mucilage contributes significantly to drought tolerance ofN. micrantha nutlets by decreasing germination under moderate osmotic stress and aiding germination after the release of this stress.

Multivariate analysis of elements from the microhabitats of selected plateaus in the Western Ghats, Maharashtra, India

The Western Ghats represents a small part of the Deccan Traps continental flood basalt province that erupted about 65 million years ago. It is an area of outstanding scenic beauty and has attracted the attention of geologists, naturalists and geomorphologists for over a century. One of the unique habitats in the Western Ghats are the rocky plateaus. Previous studies have covered plant species composition, geological and geomorphological status of the rocky plateaus. An analytical study of microhabitats and associated therophytes of four rocky plateau sites was conducted. The study sites were Durgawadi Plateau, Naneghat Plateau which are basalt outcrops and Zenda plateau and Amba Plateau, which are laterite outcrops on the escarpment of the northern Western Ghats. The results revealed a correlation between basalt and lateritic rock outcrops as well as ephemeral plant elements. All four outcrops are similar in their nutrient status but the microhabitats of these plateaus are extremely different from each other.