Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → Chine → 2010 → Studies On The Role Of Osmotic Adjustment Under Drought And Salt Stress In Desert Plant Reaumuria Soongorica

China University (2010)

Studies On The Role Of Osmotic Adjustment Under Drought And Salt Stress In Desert Plant Reaumuria Soongorica

Wang Y S

Titre : Studies On The Role Of Osmotic Adjustment Under Drought And Salt Stress In Desert Plant Reaumuria Soongorica

Auteur : Wang Y S

Grade : Doctoral Dissertation 2010

Université : China University

Résumé partiel
The term osmotic adjustment is used to imply an adaptive response : a net increase in thequantity of osmotically active solute either by uptake or by synthesis. Osmoticadjustment is considered as one of the most important adaptations of plants to drought,because it allows plants to maintain water absorption, cell turgor and metabolic activityduring periods of drought stress, and also enables quick resumption of growth whenwater becomes available again. We chose Reaumuria soongorica as our target species,which is the dominant and constructive plant of desert shrubbery vegetations in China,with high ability to tolerate stressful environments, such as drought and salinity. Due toits potential role for ecosystem function in arid- and semi-arid regions studied, the presentwork explored the underlying mechanism of osmotic adjustment and major osmoticsolutes in R. soongorica suffering from different magnitude of stress regarding to droughtand salinity, mainly focusing on the content of the inorganic ions (K+,Na+ and NO3-) andorganic solutes (proline and soluble sugar). The key results are as following:1. K+ and Na+ largely accumulated in the leaves of R. soongorica under droughtstress, especially for the Na+ content increasing continuously with drought time.Although R. soongorica is neither euhalophyte nor xero-halophyte such as Haloxylonammodendron, it does evolve the adaptive strategy to tolerate salinity. Through thecellular compartmentalization, R. soongorica is able to tolerate the high concentration ofNa+ in cell. Both K+ and Na+, especially Na+, play important roles in osmotic adjustmentof R. soongorica in this study. K+ and Na+ also tremendously accumulated in the stems,but their contents in roots did not have remarkable changes, especially the Na+ contentwas rarely affected by drought. Therefore, we conclude that when R. soongorica suffereddrought, stems could aid even act as surogate for leaves to perform many physiologicalfunctions to adapt severe environments. Leaves and stems of R. soongorica are the majororgans to accumulate K+ and Na+.2. NO3- greatly accumulated in the leaves and stems of R. soongorica, and its contentalways increased with drought time, especially in the stem, suggesting that the stem playsimportant role in the osmotic adjustment of R. soongorica and is the major organ to accumulate NO3-. In contrast to the leaves and stems, the NO3- content in rootssignificantly decreased with drought time, while in controlled plants it increased all thetime. Therefore, we presume that the root may be a store organ of NO3- in R. soongorica.When the water status is benign, NO3- can largely accumulate in the roots of R.soongorica, and then it can be transported up to shoots when water becomes rare, playingroles in the osmotic adjustment of leaves and stems and helping R. soongorica overcomesevere drought. This type of storage for NO3- is crucial for the desert plants, because thenitrogen content of the desert soil is very low, The addition of external KNO3 alleviatingthe reduction of NO3- content in the root in this experiment, suggests the increasednitrogen content of soil could compensate the lost of NO3- in the root due to thetransportation to the shoot. The addition of external KNO3 had much more effect on theNO3- content in R. soongorica than K+ and Na+, because probably the basal nitrogencontent of soil in which R. soongorica grows is lower than the optimal soil nitrogencontent required for its normal growth. The NO3 content exhibited the increasing trend inthe leaf of R. soongorica under the salt stress.3. The proline content in the leaves of R. soongorica increased in the early 20 daysduring drought treatment, and then pronouncedly decreased. The content of the prolinedid increase at early stage in the leaves of R. soongorica under long-term water deficit,but it gradually reduced with drought time until lower than that of controlled plants.Moreover, the addition of external KNO3 magnified the reduction of proline content. Theproline content in the stems of R. soongorica also increased remarkably under drought,and it did not have significant change after the addition of external KNO3. For the rootsof R. soongorica, the proline content reduced notably under drought, and this decreasingtrend was not affected by the addition of external KNO3.

Mots clés : Reaumuria soongorica, drought stress, salt stress, osmotic adjustment, osmotic solute, compatible solute, inorganic ion, cellular compartmentalization

Présentation (Globethesis)

Page publiée le 8 mai 2013, mise à jour le 4 mai 2018