Roles of glycine betaine and proline in improving plant abiotic stress resistance

Plant functional traits are the features (morphological, physiological, phenological) that represent ecological strategies and determine how plants respond to environmental factors, affect other trophic levels and influence ecosystem properties. Variation in plant functional traits, and trait syndromes, has proven useful for tackling many important ecological questions at a range of scales, giving rise to a demand for standardised ways to measure ecologically meaningful plant traits. This line of research has been among the most fruitful avenues for understanding ecological and evolutionary patterns and processes. It also has the potential both to build a predictive set of local, regional and global relationships between plants and environment and to quantify a wide range of natural and human-driven processes, including changes in biodiversity, the impacts of species invasions, alterations in biogeochemical processes and vegetation–atmosphere interactions. The importance of these topics dictates the urgent need for more and better data, and increases the value of standardised protocols for quantifying trait variation of different species, in particular for traits with power to predict plant- and ecosystem-level processes, and for traits that can be measured relatively easily. Updated and expanded from the widely used previous version, this handbook retains the focus on clearly presented, widely applicable, step-by-step recipes, with a minimum of text on theory, and not only includes updated methods for the traits previously covered, but also introduces many new protocols for further traits. This new handbook has a better balance between whole-plant traits, leaf traits, root and stem traits and regenerative traits, and puts particular emphasis on traits important for predicting species’ effects on key ecosystem properties. We hope this new handbook becomes a standard companion in local and global efforts to learn about the responses and impacts of different plant species with respect to environmental changes in the present, past and future.

/pdf/new-handbook-for-standardised-measurement-of-plant-5aljxhhg5y.pdf

New handbook for standardised measurement of plant functional traits worldwide

When exposed to stressful conditions, plants accumulate an array of metabolites, particularly amino acids. Amino acids have traditionally been considered as precursors to and constituents of proteins, and play an important role in plant metabolism and development. A large body of data suggests a positive correlation between proline accumulation and plant stress. Proline, an amino acid, plays a highly beneficial role in plants exposed to various stress conditions. Besides acting as an excellent osmolyte, proline plays three major roles during stress, i.e., as a metal chelator, an antioxidative defense molecule and a signaling molecule. Review of the literature indicates that a stressful environment results in an overproduction of proline in plants which in turn imparts stress tolerance by maintaining cell turgor or osmotic balance; stabilizing membranes thereby preventing electrolyte leakage; and bringing concentrations of reactive oxygen species (ROS) within normal ranges, thus preventing oxidative burst ...

https://www.tandfonline.com/doi/pdf/10.4161/psb.21949

Role of proline under changing environments: a review.

Abiotic stresses are one of the major constraints to crop production and food security worldwide. The situation has aggravated due to the drastic and rapid changes in global climate. Heat and drought stress are undoubtedly the two most important stresses having huge impact on growth and productivity of the crops. It is very important to understand the physiological, biochemical and ecological interventions related to these stresses for better management. A wide range of plant responses to these stresses could be generalized into morphological, physiological and biochemical responses. Interestingly, this review provides a detailed account of plant responses to heat and drought stresses with special focus on highlighting the commonalities and differences. Crop growth and yields are negatively affected by sub-optimal water supply and abnormal temperatures due to physical damages, physiological disruptions and biochemical changes. Both these stresses have multi-lateral impacts and therefore, complex in mechanistic action. A better understanding of plant responses to these stresses has pragmatic implication for remedies and management. A comprehensive account of conventional as well as modern approaches to deal with heat and drought stresses have also been presented here. A side-by-side critical discussion on salient responses and management strategies for these two important abiotic stresses provides a unique insight into the phenomena. A holistic approach taking into account the different management options to deal with heat and drought stress simultaneously could be a win-win approach in future.

/pdf/crop-production-under-drought-and-heat-stress-plant-4citjxbeya.pdf

Crop Production under Drought and Heat Stress: Plant Responses and Management Options

Plants exposed to heavy metals accumulate an array of metabolites, some to high millimolar concentrations. This review deals with N-containing metabolites frequently preferentially synthesized under heavy metal stress such as Cd, Cu, Ni, and Zn. Special focus is given to proline, but certain other amino acids and oligopeptides, as well as betaine, polyamines, and nicotianamine are also addressed. Particularly for proline a large body of data suggests significant beneficial functions under metal stress. In general, the molecules have three major functions, namely metal binding, antioxidant defence, and signalling. Strong correlative and mechanistic experimental evidence, including work with transgenic plants and algae, has been provided that indicates the involvement of metal-induced proline in metal stress defence. Histidine, other amino acids and particularly phytochelatins and glutathione play a role in metal binding, while polyamines function as signalling molecules and antioxidants. Their accumulation needs to be considered as active response and not as consequence of metabolic dys-regulation.

The significance of amino acids and amino acid-derived molecules in plant responses and adaptation to heavy metal stress

http://nhjy.hzau.edu.cn/kech/ssyy/qysd/njsl/21.pdf

Potential biochemical indicators of salinity tolerance in plants

Soil salinity is a major environmental constraint to crop productivity worldwide. The “biological” approach to this problem focuses on the management, exploitation, or development of plants able to thrive on salt‐affected soils. This chapter reviews strategies by which plants can be enabled to grow on saline soils. The first strategy is to prime seeds before planting by treating them with inorganic or organic chemicals and/or with high or low temperatures. The second strategy involves exogenous application of organic chemicals, such as glycine betaine, proline, or plant growth regulators, or inorganic chemicals to plants under salinity stress. Considerable improvements in growth and yield have been reported in a number of crops using these approaches. The third strategy is to employ selection and breeding. Major efforts have been made to develop salt‐tolerant lines or cultivars of crops using conventional plant breeding. However, the complexity of the tolerance mechanisms, lack of selection criteria, and variation in responses of plants at different developmental stages have resulted in only limited success. The emphases for developing salt‐tolerant lines/cultivars are now on marker‐assisted breeding and genetic transformation. The development of salt‐tolerant transgenic plants is still at an early stage but may become increasingly more effective as better knowledge of the complex mechanisms involved in plant salt tolerance is acquired. Furthermore, the rapid expansion in knowledge on genomics and proteomics will undoubtedly accelerate the transgenic and molecular breeding approaches However, to date, there are few conclusive reports indicating successful performance of transgenic cultivars under natural stressful environments.

Some Prospective Strategies for Improving Crop Salt Tolerance

http://directory.umm.ac.id/Data%20Elmu/jurnal/P/PlantScience/PlantScience_Elsevier/Vol159.Issue2.2000/5462.pdf

In vitro selection and characterisation of a drought tolerant clone of Tagetes minuta

The essential oils from aerial parts of Tagetes minuta L. grown in Egypt, South Africa and the UK were obtained by hydrodistillation. Although they had similar constituents, the oils had different percentage compositions. Dihydrotagetone was the most abundant component of the oils from the UK (34.3 and 54.1%), while the oils from South Africa and Egypt were characterized by a high content of cis-β-ocimene (50.9 and 32.0%, respectively). The oils exhibited antibacterial activity, especially against Gram-positive bacteria. Antimicrobial activity was greater in oils from the UK than in oils from Egypt or South Africa, irrespective of whether the UK plants had been grown in a greenhouse or in the field. The minimum inhibitory concentrations (MIC) for the oil from UK greenhouse-grown plants were 6.25-25 μg/mL for Gram-positive bacteria and 25-50 μg/mL for Gram-negative bacteria, with the lowest MIC of 6.25 μg/mL against Streptococcus faecalis. Oil from plants from South Africa had MICs of 50-100 μg/mL against Gram-positive and Gram-negative bacteria. The MICs of oil from plants from Egypt against all tested bacteria except Pseudomonas aeruginosa and Salmonella typhi were half of the MICs of oil from plants from South Africa.

Antibacterial activity of Tagetes minuta L. (Asteraceae) essential oil with different chemical composition

A drought-tolerant clone of Tagetes minuta L. (Asteraceae) was selected in vitro on a medium containing 60 mM mannitol. In the greenhouse, a decrease in soil field capacity (FC) from 100 to 40 % reduced oil yield by 49, 71 and 71 % for drought-tolerant, non-drought tolerant cloned and seed-grown plants, respectively. In soil at 40 % FC, the drought-tolerant clone had the highest leaf dry weight and oil yield. At 100 % FC, there was no significant difference in leaf dry weight, but the drought-tolerant clone had a significantly higher percentage oil content and yield than seed-grown plants. The main components of the oil were monoterpenes of which trans- and cis-tagetone together were 52.3 % - 64.2 %. Drought significantly altered the content of some oil components.

P.J.C. Harris

Papers

Potential biochemical indicators of salinity tolerance in plants

Some Prospective Strategies for Improving Crop Salt Tolerance

In vitro selection and characterisation of a drought tolerant clone of Tagetes minuta

Antibacterial activity of Tagetes minuta L. (Asteraceae) essential oil with different chemical composition

Effect of drought stress on the yield and composition of volatile oils of drought-tolerant and non-drought-tolerant clones of Tagetes minuta.