Browsing by Subject "drought tolerance"

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  • Mäkelä, Pirjo; Vaarala, L; Rajalahti, R; Rajala, A; PeltonenSainio, P (1997)
  • Lizarazo Torres, Clara Isabel (Helsingfors universitet, 2010)
    Drought is one of the most important abiotic stresses that causes significant reductions in crop yield, and thus hinders the food security of the growing world population. In consequence, it is urgent to select crops able to resist drought, maintain high yield and have a good nutritive content. The purpose of this project was to evaluate the responses of different accessions of Andean lupin to drought stress, and identify if there are significant differences in their physiological responses. To identify germplasm for further investigation, thirty accessions of Lupinus mutabilis Sweet. and one accession of L. albococcineus Hort. were screened in two sets, A of 15 and B of 16 accessions. From these sets, four lines were chosen on the basis of extreme values in the measurements, and this set of four was investigated in depth (set C). In all experiments, ten seeds of each chosen accession were sown in pots and grown in a glasshouse with 22°C, 18 h days and 18°C, 6 h nights, and were well watered until day 50 after planting. The pots were arranged in a randomized complete block design. The eight most uniform plants were chosen, and four were exposed to water stress while watering of the other four was continued. Water stress consisted of controlled water loss from the soil, 20% water holding capacity at 2% per day over 9 days, so the soil reached 2% moisture content and was held at this level for 2 days more. In all experiments, leaf temperature, stomatal conductance, relative water content, water potential, ion membrane leakage, and shoot dry weight were measured and transpiration efficiency was calculated. In set C, carbon isotope discrimination, root length, root dry matter, proline content and soluble sugar content were also determined. The analysis of set A and B revealed significant differences between treatments for all the parameters measured, except for relative water content, and there were also differences amongst accessions in certain parameters. PI 457972 and PI 457981 were selected for further investigation because of their low stomatal conductance under water stress conditions and low water use, and PI 510572 was selected as sensitive to drought stress due to its high water use, ion membrane leakage and water potential under water stress conditions. In addition AC 2792 (L. albococcineus) was selected due to its low stomatal conductance and water use, and high leaf temperature under water stress conditions. In the final experiment, PI 457981 and PI 457972 appeared to avoid drought through appropriate stomatal characteristics. PI 457981 showed low stomatal conductance, high leaf temperature and also high root length, similarly, accession PI 457972 showed low water potential, low stomatal conductance, low carbon isotope discrimination and accumulation of soluble sugars. Accession PI 510572 contrasted for these stomatal traits, but interestingly it showed low membrane ion leakage, high proline content and soluble sugars content, suggesting that it was capable of drought tolerance by osmotic adjustment. Finally, accession AC2792 showed low water use, low water potential and low carbon isotope discrimination. This survey thus identified accessions of Andean lupin that were able to avoid drought stress through stomatal traits and root traits, and other that were able to tolerate drought through the accumulation of osmotically active substances. Thus, there are good prospects for breeding of Andean lupin to improve its drought resistance.
  • Ramírez-Valiente, José-Alberto; Aranda, Ismael; Sanchez-Gomez, David; Rodriguez-Calcerrada, Jesus; Valladares, Fernando; Robson, Thomas Matthew (2019)
    In Mediterranean-type ecosystems, drought is considered the main ecological filter for seedling establishment. The evergreen oaks Quercus ilex L. and Quercus suber L. are two of the most abundant tree species in the Mediterranean Basin. Despite their shared evergreen leaf habit and ability to resist low soil water potentials, traditionally it has been suggested that Q. ilex is better suited to resist dry conditions than Q. suber. In this study, we examined how seedlings of Q. ilex and Q. suber grown in sandy soils responded to different levels of water availability using natural dry conditions and supplemental watering. Specifically, we estimated survival and water status of seedlings and explored the role of acorn mass and belowground biomass in seedling performance. To our surprise, Q. suber was better able to survive the summer drought in our experiment than Q. ilex. Nearly 55% of the Q. suber seedlings remained alive after a 2-month period without rain or supplemental water, which represents almost 20% higher survival than Q. ilex over the same period. At the end of the dry period, the surviving seedlings of Q. suber had strikingly higher water potential, potential maximum quantum yield of photosystem II (F-v/F-m) and stomatal conductance (g(s)) than those of Q. ilex. Acorn mass was associated with the probability of survival under dry conditions; however, it did not explain the differences in survival or water status between the species. In contrast, Q. suber had a higher root ratio and root: shoot ratio than Q. ilex and these traits were positively associated with predawn leaf water potential, F-v/F-m, g(s) and survival. Taken together, our results suggest that the higher relative investment in roots by Q. suber when growing in a sandy acidic substrate allowed this species to maintain better physiological status and overall condition than Q. ilex, increasing its probability of survival in dry conditions.
  • Wang, Ai-Fang; Di, Bao; Repo, Tapani; Roitto, Marja; Zhang, Gang (2020)
    Background and Objectives: Drought occurs more frequently in Northern China with the advent of climate change, which might increase the mortality of tree seedlings after afforestation due to hydraulic failure. Therefore, investigating water relations helps us understand the drought tolerance of tree seedlings. Electrical impedance spectroscopy (EIS) is widely used to assess the responses of plant tissues to stress factors and may potentially reveal the water relations of cells. The aim of this study is to reveal the relationships between EIS and water related parameters, produced by pressure-volume (PV) curves in lacebark pine (Pinus bungeanaZucc.) seedlings reacting to drought stress. Materials and Methods: Four-year-old pot seedlings were divided into three parts (0, 5, and 10 days of drought) before planting, the treated seedlings were then replanted, and finally exposed to post-planting drought treatments with the following soil relative water contents: (i) adequate irrigation (75%-80%), (ii) light drought (55%-60%), (iii) moderate drought (35%-40%), and (iv), severe drought (15%-20%). During the post-planting growth phase, the EIS parameters of needles and shoots, and the parameters of PV curves, were measured coincidently; thus, the correlations between them could be obtained. Results: The extracellular resistance (r(e)) of needles and shoots were substantially reduced after four weeks of severe post-planting drought stress. Meanwhile, the osmotic potential at the turgor-loss point (psi(tlp)) and the saturation water osmotic potential (psi(sat)) of shoots decreased after drought stress, indicating an osmotic adjustment in acclimating to drought. The highest correlations were found between the intracellular resistance (r(i)) of the shoots and psi(tlp) and psi(sat). Conclusions: EIS parameters can be used as a measure of drought tolerance. The change in intracellular resistance is related to the osmotic potential of the cell and cell wall elasticity. Extracellular resistance is a parameter that shows cell membrane damage in response to drought stress in lacebark pine seedlings.