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Ben-Gurion University of the Negev (2018)

Salt-tolerance mechanisms in jojoba (Simmondsia chinensis) : the role of the root system

Zhao, Lina

Titre : Salt-tolerance mechanisms in jojoba (Simmondsia chinensis) : the role of the root system

Auteur : Zhao, Lina

Etablissement de soutenance : Ben-Gurion University of the Negev

Grade : Master of Science (MS) 2018

Résumé
Salinity is one of the most important abiotic stresses which adversely affect plant productivity and quality, about 20% of total agricultural land are salt-affected all over the world. Salt stress severely limits the growth and development of plants via physiological and biochemical reactions. Thus, it is essential to improve plant tolerance to salt. To achieve this objective, it is vital to understand how salt stress affects plant growth and development and to reveal mechanisms underlying tolerance to salt in naturally tolerant plants. Jojoba [Simmondsia chinensis] is a perennial, evergreen woody shrub adapted to extremely harsh environments, known to withstand very high salinity. The Benzioni variety of jojoba was used in this study. To investigate the salt tolerance strategy and evaluate the role and contribution of the roots to the salt avoidance mechanisms functioning in jojoba, we examined both above ground and below ground parameters of jojoba planted in white perlite media. Randomized block design was used in the experiment, including eight different (1.74, 3.70, 5.56, 7.93, 9.76, 11.63, 13.92, and 15.46 dS m 1 ) irrigation water salt concentration treatments. Transparent minirhizotron observation tubes (MROTs) were installed into the containers with the jojoba plants. Root photographs were taken every three to five weeks using a minirhizotron system (MR) during different developmental stages and properties including root count, root length, root diameter, and root color (age) were quantified. Furthermore, agronomic traits, photosynthetic properties, and minerals in the leaves and roots were measured Jojoba was found to be highly tolerant to root zone salinity. The percentage of light brown roots to total roots was found to always be highest in all salinity treatments throughout the experiment period and almost no dead dead roots were observed. Root length, root diameter, root volume and root length density were not affected by salinity. Number of branch points, internodes and flowers were not affected by salinity but high salinity water irrigation lead to increased yield in jojoba. Photosynthetic traits were reduced by salinity. The concentration of N was not affected by salinity in both leaves and roots, while P and K concentration was reduced in leaves and no significant affected in roots, but Na, Cl, Mg and Ca concentration increased as a function of increasing salinity level. More mineral ion accumulation occurred in roots compare to leaves, however, high concentration of ions was found in mature leaves with high water content. In our study has revealed jojoba had a strong interaction between root and leaf under salinity treatment. In conclusion, the results presented in this study advance our understanding of the unique and complex mechanisms of response, tolerance and adaptation in jojoba under conditions of salinity.

Mots clés : Jojoba, salinity stress, minirhizotron, root, leaf, agronomic traits, photosynthetic traits, mineral ion

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Page publiée le 11 janvier 2022