Plants often encounter unfavorable environmental conditions because of their sessile lifestyle These adverse factors greatly affect the geographic distribution of plants, as well as their growth and productivity Drought stress is one of the premier limitations to global agricultural production due to the complexity of the water-limiting environment and changing climate Plants have evolved a series of mechanisms at the morphological, physiological, biochemical, cellular, and molecular levels to overcome water deficit or drought stress conditions The drought resistance of plants can be divided into four basic types-drought avoidance, drought tolerance, drought escape, and drought recovery Various drought-related traits, including root traits, leaf traits, osmotic adjustment capabilities, water potential, ABA content, and stability of the cell membrane, have been used as indicators to evaluate the drought resistance of plants In the last decade, scientists have investigated the genetic and molecular mechanisms of drought resistance to enhance the drought resistance of various crops, and significant progress has been made with regard to drought avoidance and drought tolerance With increasing knowledge to comprehensively decipher the complicated mechanisms of drought resistance in model plants, it still remains an enormous challenge to develop water-saving and drought-resistant crops to cope with the water shortage and increasing demand for food production in the future

General mechanisms of drought response and their application in drought resistance improvement in plants

Saline soils are a major issue for agriculture because salt turns agronomically useful lands into unproductive areas. The United Nations Environment Program estimates that approximately 20 % of agricultural land and 50 % of cropland in the world is salt-stressed. Soil salinisation is reducing the area that can be used for agriculture by 1–2 % every year, hitting hardest in the arid and semi-arid regions. Salinity decreases the yield of many crops because salt inhibits plant photosynthesis, protein synthesis and lipid metabolism. Plant-growth-promoting rhizobacteria (PGPR), beneficial bacteria that live in the plant root zone named the rhizosphere, is one of the solutions to solve this issue. Indeed rhizobacteria counteract osmotic stress and help plant growth. This article reviews the benefits of plant-growth-promoting rhizobacteria for plants growing in saline soils. The major points are (1) plants treated with rhizobacteria have better root and shoot growth, nutrient uptake, hydration, chlorophyll content, and resistance to diseases; (2) stress tolerance can be explained by nutrient mobilisation and biocontrol of phytopathogens in the rhizosphere and by production of phytohormones and 1-aminocyclopropane-1-carboxylate deaminase; (3) rhizobacteria favour the circulation of plant nutrients in the rhizosphere; (4) rhizobacteria favour osmolyte accumulation in plants; (5) plants inoculated with rhizobacteria have higher K+ ion concentration and, in turn, a higher K+/Na+ ratio that favour salinity tolerance; and (6) rhizobacteria induce plant synthesis of antioxidative enzymes that degrade reactive oxygen species generated upon salt shock.

/pdf/plant-growth-promoting-rhizobacteria-to-improve-crop-growth-27x18ej8zd.pdf

Plant-growth-promoting rhizobacteria to improve crop growth in saline soils: a review

Spring phenology of temperate forest trees is optimized to maximize the length of the growing season while minimizing the risk of freezing damage. The release from winter dormancy is environmentally mediated by species-specific responses to temperature and photoperiod. We investigated the response of early spring phenology to temperature and photoperiod at different stages of dormancy release in cuttings from four temperate tree species in controlled environments. By tracking bud development, we were able to identify the onset of bud swelling and bud growth in Acer pseudoplatanus L., Fagus sylvatica L., Quercus petraea (Mattuschka) Liebl. and Picea abies (L.) H. Karst. At a given early stage of dormancy release, the onset and duration of the bud swelling prior to bud burst are driven by concurrent temperature and photoperiod, while the maximum growth rate is temperature dependent only, except for Fagus, where long photoperiods also increased bud growth rates. Similarly, the later bud burst was controlled by temperature and photoperiod (in the photoperiod sensitive species Fagus, Quercus and Picea). We conclude that photoperiod is involved in the release of dormancy during the ecodormancy phase and may influence bud burst in trees that have experienced sufficient chilling. This study explored and documented the early bud swelling period that precedes and defines later phenological stages such as canopy greening in conventional phenological works. It is the early bud growth resumption that needs to be understood in order to arrive at a causal interpretation and modelling of tree phenology at a large scale. Classic spring phenology events mark visible endpoints of a cascade of processes as evidenced here.

Photoperiod and temperature responses of bud swelling and bud burst in four temperate forest tree species

Changes in spring and autumn phenology of temperate plants in recent decades have become iconic bio-indicators of rapid climate change. These changes have substantial ecological and economic impacts. However, autumn phenology remains surprisingly little studied. Although the effects of unfavorable environmental conditions (e.g., frost, heat, wetness, and drought) on autumn phenology have been observed for over 60 y, how these factors interact to influence autumn phenological events remain poorly understood. Using remotely sensed phenology data from 2001 to 2012, this study identified and quantified significant effects of a suite of environmental factors on the timing of fall dormancy of deciduous forest communities in New England, United States. Cold, frost, and wet conditions, and high heat-stress tended to induce earlier dormancy of deciduous forests, whereas moderate heat- and drought-stress delayed dormancy. Deciduous forests in two eco-regions showed contrasting, nonlinear responses to variation in these explanatory factors. Based on future climate projection over two periods (2041-2050 and 2090-2099), later dormancy dates were predicted in northern areas. However, in coastal areas earlier dormancy dates were predicted. Our models suggest that besides warming in climate change, changes in frost and moisture conditions as well as extreme weather events (e.g., drought- and heat-stress, and flooding), should also be considered in future predictions of autumn phenology in temperate deciduous forests. This study improves our understanding of how multiple environmental variables interact to affect autumn phenology in temperate deciduous forest ecosystems, and points the way to building more mechanistic and predictive models.

https://www.pnas.org/content/pnas/112/44/13585.full.pdf

Deciduous forest responses to temperature, precipitation, and drought imply complex climate change impacts.

Whether and how the timing of extreme events affects the direction and magnitude of legacy effects on tree growth is poorly understood. In this study, we use a global database of Ring-Width Index (RWI) from 2,500 sites to examine the impact and legacy effects (the departure of observed RWI from expected RWI) of extreme drought events during 1948-2008, with a particular focus on the influence of drought timing. We assessed the recovery of stem radial growth in the years following severe drought events with separate groupings designed to characterize the timing of the drought. We found that legacies from extreme droughts during the dry season (DS droughts) lasted longer and had larger impacts in each of the 3 years post drought than those from extreme droughts during the wet season (WS droughts). At the global scale, the average integrated legacy from DS droughts (0.18) was about nine times that from WS droughts (0.02). Site-level comparisons also suggest stronger negative impacts or weaker positive impacts of DS droughts on tree growth than WS droughts. Our results, therefore, highlight that the timing of drought is a crucial factor determining drought impacts on tree recovery. Further increases in baseline aridity could therefore exacerbate the impact of punctuated droughts on terrestrial ecosystems.

/pdf/drought-timing-influences-the-legacy-of-tree-growth-recovery-1zdrzbv4lk.pdf

Drought timing influences the legacy of tree growth recovery.

Excellent book is always being the best friend for spending little time in your office, night time, bus, and everywhere. It will be a good way to just look, open, and read the book while in that time. As known, experience and skill don't always come with the much money to acquire them. Reading this book with the PDF physiological plant ecology ecophysiology and stress physiology of function groups will let you know more things.

Marcel Abendroth

Papers

Physiological Plant Ecology Ecophysiology And Stress Physiology Of Functional Groups