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Ben-Gurion University of the Negev (2019)

Plant water-uptake effects on salt distribution at the root-soil interface

Perelman, Adi

Titre : Plant water-uptake effects on salt distribution at the root-soil interface

תנועת מים בצמח והשפעתה על הצטברות נתרן באזור המגע בין השורש לקרקע.

Auteur : Perelman, Adi,

Etablissement de soutenance : Ben-Gurion University of the Negev

Grade : Doctor of Philosophy (PhD) 2019

Résumé partiel
Salinity stress is one of the major abiotic stresses that impact plant growth and development, resulting in yield reduction. Thus, salinity constitutes a serious threat to agricultural productivity, especially in arid and semi-arid regions. The current estimation is that 20% of total cultivated and 33% of irrigated agricultural lands worldwide are afflicted by salinity. Moreover, the salinization rate of lands is increasing by 10% per year. Growth and development of plants under salinity is often limited by the roots’ ability to extract water from the soil due to osmotic stress, alongside other harmful phenomena such as ion toxicity and ion disequilibrium which interfere with nutrient uptake and photosynthesis and cause overproduction of reactive oxygen species (ROS).

Roots are usually the first plant organ to "feel" salinity stress in the soil. Salinity causes changes in growth, morphology and physiology of the roots, thus affecting water and ion uptake, which in turn causes reduction in root hydraulic conductance (KR). Root hydraulic conductance is an important factor determining water supply to the plant. Reduction in root hydraulic conductance is directly proportional to plant growth and total dry matter production. Understanding the water gradients in the soil-plant-atmosphere continuum and the resistances that control water movement through this continuum is important for revealing the influence of salinity on root structure and functions.

Transpiration rate is assumed to influence salt accumulation around roots and thus affect the root felt concentration, which impacts the whole plant sensitivity. Water moves through the soil into the roots and then to the transpiring leaves along pressure gradients, therefore, any factor influencing transpiration eventually will impact root water uptake. Furthermore, there is a correlation between the amount of transpired water and mineral uptake, so it is possible to assume that Na+ movement toward the root will also be affected by transpiration rate. Previous studies reported that plants seem to be less sensitive to salinity stress when grown under conditions of low light intensity and/or high relative humidity which probably lead to low transpiration rate. Transpiration rate was also found to affect Na+ concentrations around the roots compared with the bulk soil. Na+ accumulation in the bulk is generally considered in different models, while its accumulation at the root-soil interface is usually not.

The most common model in use today to predict the impact of salinity on crop yield is the Maas and Hoffman model (1976). In this model, when salinity in the soil increases beyond a certain threshold, crop yield will decrease at a fixed rate. Thus, it is highly important to predict salinization and its impact on crops. Current models do not consider the impact of the transpiration rate on plant salt tolerance, although it affects plant water uptake and thus salt accumulation around the roots, consequently influencing the plant’s sensitivity to salinity. Better model parametrization can improve the prediction of real salinity effects on crop growth and yield.

Présentation et version intégrale (PRIMO)

Page publiée le 10 décembre 2022