Konstantina Kocheva

Bio: Konstantina Kocheva is an academic researcher from Bulgarian Academy of Sciences. The author has contributed to research in topics: Osmotic shock & Chlorophyll fluorescence. The author has an hindex of 9, co-authored 28 publications receiving 321 citations.

Wheat plant selection for high yields entailed improvement of leaf anatomical and biochemical traits including tolerance to non-optimal temperature conditions.

Abstract: Assessment of photosynthetic traits and temperature tolerance was performed on field-grown modern genotype (MG), and the local landrace (LR) of wheat (Triticum aestivum L.) as well as the wild relative species (Aegilops cylindrica Host.). The comparison was based on measurements of the gas exchange (A/ci, light and temperature response curves), slow and fast chlorophyll fluorescence kinetics, and some growth and leaf parameters. In MG, we observed the highest CO2 assimilation rate [Formula: see text] electron transport rate (Jmax) and maximum carboxylation rate [Formula: see text]. The Aegilops leaves had substantially lower values of all photosynthetic parameters; this fact correlated with its lower biomass production. The mesophyll conductance was almost the same in Aegilops and MG, despite the significant differences in leaf phenotype. In contrary, in LR with a higher dry mass per leaf area, the half mesophyll conductance (gm) values indicated more limited CO2 diffusion. In Aegilops, we found much lower carboxylation capacity; this can be attributed mainly to thin leaves and lower Rubisco activity. The difference in CO2 assimilation rate between MG and others was diminished because of its higher mitochondrial respiration activity indicating more intense metabolism. Assessment of temperature response showed lower temperature optimum and a narrow ecological valence (i.e., the range determining the tolerance limits of a species to an environmental factor) in Aegilops. In addition, analysis of photosynthetic thermostability identified the LR as the most sensitive. Our results support the idea that the selection for high yields was accompanied by the increase of photosynthetic productivity through unintentional improvement of leaf anatomical and biochemical traits including tolerance to non-optimal temperature conditions.

A diffusion approach to the electrolyte leakage from plant tissues

Abstract: The exchange of ions between plant tissues and the external solution in vitro exhibits prominent biphasic kinetics. This is generally ascribed to the different contribution of the two compartments - apoplast and symplast - involved in the process. In this regard, an electro-diffusion, model of the leakage is proposed in the paper. On the basis of the balance of fluxes through the plasmalemma and the cell wall, a system of differential equations describing the ion concentration in the outer solution is found. For a wide range of the system's coefficients, its behaviour is well approximated by a previously obtained analytical function. The values of the function's parameters, derived from the fit with experimental data, correlate adequately with the water deficit conditions of the samples. Hence, these parameters may be used to characterize the physiological status of the investigated plants.

Changes in Water Status, Membrane Stability and Antioxidant Capacity of Wheat Seedlings Carrying Different Rht‐B1 Dwarfing Alleles under Drought Stress

Abstract: Water deficiency is a major constraint to wheat productivity in drought prone regions. The wheat DELLA-encoding height-reducing genes (Rht) are associated with significant increase in grain yield. However, the knowledge of their benefit in dry environments is insufficient. The objective of the study was to examine the effect of induced drought on leaf water content, level of oxidative stress, cell membrane stability, accumulation of osmoprotectants and activity of some antioxidant enzymes in wheat near-isogenic lines carrying the alleles Rht-B1b (semidwarfing) and Rht-B1c (dwarfing) in comparison with the tall control Rht-B1a. Six-day-long water deprivation was imposed at seedling stage. Plants carrying Rht-B1c and, to a lesser extent, those carrying Rht-B1b performed better under stress compared with Rht-B1a in terms of more sustained membrane integrity, enhanced osmoregulation and better antioxidant defence. These differential responses could reflect pleiotropic effects of the Rht-B1 gene associated with the accumulation of the mutant gene product, that is, altered DELLA proteins, or might be related to allelic variations at neighbouring loci carrying candidate genes for proteins with a major role in plant water regulations and stress adaptation. These findings might be of importance to breeders when introducing Rht-B1 alleles into wheat cultivars designed to be grown in drought liable regions.

Wheat Rht‐B1 Dwarfs Exhibit Better Photosynthetic Response to Water Deficit at Seedling Stage Compared to the Wild Type

Abstract: Wheat reduced height (Rht) genes encode modified DELLA proteins, which are gibberellin insensitive, accumulate under stress, restrain growth and affect plant stress response. The seedling reaction to soil water deficit regarding leaf gas exchange and chlorophyll fluorescence was compared in near-isogenic lines carrying the alleles Rht-B1a (tall), Rht-B1b (semi-dwarfing) and Rht-B1c (dwarfing) and was related to leaf water content and anatomy. Under drought, Rht-B1c line was characterized by less decreased CO2 assimilation, delayed non-stomatal limitation of photosynthesis and higher instantaneous water use efficiency. The functional state of its photosynthetic apparatus was better preserved as evidenced by the less decreased actual quantum yield (ΦPSII) and potential maximum quantum yield (Fv/Fm) of PSII, and the less increased quantum yield of non-regulated energy dissipation (ΦNO). Rht-B1b line also tended to perform better than Rht-B1a, but differences were less pronounced. Although the leaves of both dwarf lines were smaller, thicker and more pubescent, their water content was not higher in comparison with the tall line. Nevertheless, in Rht-B1c, leaf thickness was less decreased and mesophyll cells were less shrunk under drought. The more effective performance of the photosynthetic machinery of dwarf lines under water deficit could be explained by a combination of morpho-anatomical and metabolic characteristics.

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

Abstract: 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

Drought Stress Impacts on Plants and Different Approaches to Alleviate Its Adverse Effects.

Abstract: Drought stress, being the inevitable factor that exists in various environments without recognizing borders and no clear warning thereby hampering plant biomass production, quality, and energy. It is the key important environmental stress that occurs due to temperature dynamics, light intensity, and low rainfall. Despite this, its cumulative, not obvious impact and multidimensional nature severely affects the plant morphological, physiological, biochemical and molecular attributes with adverse impact on photosynthetic capacity. Coping with water scarcity, plants evolve various complex resistance and adaptation mechanisms including physiological and biochemical responses, which differ with species level. The sophisticated adaptation mechanisms and regularity network that improves the water stress tolerance and adaptation in plants are briefly discussed. Growth pattern and structural dynamics, reduction in transpiration loss through altering stomatal conductance and distribution, leaf rolling, root to shoot ratio dynamics, root length increment, accumulation of compatible solutes, enhancement in transpiration efficiency, osmotic and hormonal regulation, and delayed senescence are the strategies that are adopted by plants under water deficit. Approaches for drought stress alleviations are breeding strategies, molecular and genomics perspectives with special emphasis on the omics technology alteration i.e., metabolomics, proteomics, genomics, transcriptomics, glyomics and phenomics that improve the stress tolerance in plants. For drought stress induction, seed priming, growth hormones, osmoprotectants, silicon (Si), selenium (Se) and potassium application are worth using under drought stress conditions in plants. In addition, drought adaptation through microbes, hydrogel, nanoparticles applications and metabolic engineering techniques that regulate the antioxidant enzymes activity for adaptation to drought stress in plants, enhancing plant tolerance through maintenance in cell homeostasis and ameliorates the adverse effects of water stress are of great potential in agriculture.

Quantitative changes in protein expression of cadmium‐exposed poplar plants

Abstract: Cadmium (Cd) pollution is a worldwide major concern having, among others, deleterious effects on plants. In the present work, the effects of a 20 microM Cd exposure in hydroponics culture during 14 days were evaluated in young poplar leaves. Proteins were analysed by 2-D DIGE, followed by MALDI-TOF-TOF identification. Additionally, growth and other physiological parameters were monitored during the experiment. Treated plants exhibited an inhibition of growth and visual symptoms appeared after 7 days. A significant accumulation of Cd in all organs was recorded by ICP-MS analysis. A number of changes in the expression of proteins with various functions were identified; in particular a decreased abundance of oxidative stress regulating proteins, whereas pathogenesis-related proteins showed a drastic increase in abundance. Furthermore, a large number of proteins involved in carbon metabolism showed a decrease in abundance, while proteins involved in remobilizing carbon from other energy sources were upregulated. In conclusion, the negative effect of Cd could be explained by a deleterious effect on protein expression from the primary carbon metabolism and from the oxidative stress response mechanism. Accumulation of Cd in stems of poplar, coupled with a low impact of Cd on physiological parameters, promotes the use of poplar trees for phytoremediation purposes.