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Accueil du site → Doctorat → Italie → Physiological and biochemical responses and feedstock composition of Tamarix spp. subjected to salt and drought stress:possibilities of biomass use for energy production in arid and degraded lands

Università degli studi della Tuscia - Viterbo (2012)

Physiological and biochemical responses and feedstock composition of Tamarix spp. subjected to salt and drought stress:possibilities of biomass use for energy production in arid and degraded lands

Dawalibi, Victoria

Titre : Physiological and biochemical responses and feedstock composition of Tamarix spp. subjected to salt and drought stress : possibilities of biomass use for energy production in arid and degraded lands

Risposte fisiologiche e biochimiche in Tamarix spp. sottoposte a stress idrico e salino : possibilità di impiego della biomassa per la produzione di energia in terre aride

Auteur : Dawalibi, Victoria

Université de soutenance : Università degli studi della Tuscia - Viterbo

Grade : Tesi di dottorato di ricerca 2012

Résumé
Tamarix trees are considered of particular interest for afforestation and reforestation of degraded areas, because they were noticed to establish and grow well in wide spectrum of edaphic, contrasting, and extreme environmental conditions. A better understanding of the functional mechanisms enabling Tamarix to adapt to extreme conditions is important, for a more insightful selection of the best ones, intended to be used for biomass production and conservation purposes in arid zones. For this scope, two trials of short period were conducted in semi-controlled conditions, during which two species of Tamarix (T. aphylla and T. jordanis) collected from Negev desert were exposed to salt, drought and combined stress. The first trial was executed at mild level of stress : salt (150mM), drought (50 % F.C.) ; the second trial was more severe : salt (350mM), drought (30% F.C.). Physiological and biochemical responses and growth were studied regularly during the experiments. The results of the experiments, showed the highest tolerance of T. jordanis to salt stress up to 350 mM. The maintenance of high amount of carbohydrates, high capacity of carbon assimilation, and active growth could be considered as potential and early markers for salt tolerance of Tamarix spp. On the other hand, the growth and biomass displayed highest performance of T. aphylla than T. jordanis in mild dry conditions. The highest accumulation of sugar and the highest relative water content in T. aphylla were suggested among their acclimatory mechanisms under mild drought (50% F.C.). Combined stress was shown to be additive in lowering performance of plants relative to salt and drought stress applied alone. Proline accumulation in both species was suggested to be a storage form of nitrogen for use under combined stress, rather than a principal osmoregulator. Given the high productivity of some Tamarix spp. cultivated in arid and degraded lands (Eshel et al., 2010), it was also investigated the possible use of Tamarix biomass for bioethanol production, in the second step of our study. Several samples were collected from different natural and experimental plantations in Mediterranean area. Differences in ligncoelulose matrix among different locations, age, and species were evaluated. The results showed that the growing sites had significant effect on structural sugars content with no apparent significant influence on lignin. There were no significant variations in structural sugars and lignin between different species and ages. Despite the limited number of samples, the results, in general, have shown a good quality of lignocellulosic biomass of tamarisk for the production of bioethanol. The content of hexose and pentose sugars found in the samples analyzed was highly comparable to other species already used in the production of biofuels such as eucalyptus (43-45% cellulose). However, some obstacles from presence of ash and extractives in high amount should be taken into account, and better understanding of cultural practices effect on these substances is essential prior to any process of sugar conversion to ethanol

Mots clés : Desertification ; Tamarix ; Salinity ; Drought ; Biomass ; Bioethanol ; Desertificazione ; Salinità ; Aridità ; Biomassa ; Bioetanolo ; AGR/05

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Page publiée le 25 novembre 2013, mise à jour le 15 mars 2019