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

Titre : Anatomía, fisiología y bioquímica de la raíz de plántulas de frijol tepari (Phaseolus acutifolius A. Gray var. latifolius) en estrés hídrico

Auteur : Orduño Cruz, Andrés

Etablissement de soutenance : Colegio de Postgraduados (COLPOS) Consejo Nacional de Ciencia y Tecnología (CONACYT)

Grade : Doctorado 2008

Résumé
This research was performed to document the morphological, anatomical, physiological, and biochemical changes that root of tepary bean seedlings has (Phaseolus acutifolius A. Gray var. latifolius) in the cultivars “Brown‐Yellow‐Red” (RYB), “Black”, “Tohono Oodham”, and “Blanco de Sinaloa” ; when it grows at water potentials (ΨW ) : ‐0.03, ‐0.07, ‐0.51, and ‐ 2.01 MPa in the substrate. And this would contribute to reevaluate the use of tepay bean as a food and important gene pool ; because of tepary bean use has been replaced as a food source and many cultivars in Mexico and southern United States are prone to disappear. The root growth of the cultivars proved to be influenced by humidity and was proportional to the level substrate water potential. Root length was greater in moderately dry substrates than in humid or dry ones ; which confirms that root tepary beans is adapted to growth in arid environments. The relative water content (RWC) in the root tissue remained high and constant even when Ψw in the substrate went from –0.51 to – 2.01 MPa. At anatomical level, the effect of Ψw on length and radial growth was heterogeneous among the cultivars of tepary beans and allowed to observe that root growth is modulated by the substrate humidity. The arrangement and number of cells of the different tissues was similar among cultivars. There was, however, a significant difference (P≤0.05) in cell size among cultivars and substrate water levels, with a tendency to decrease with lower Ψw in the substrate. Radial growth of the root showed a progressive natural increase in diameter in the first 15 mm ; thin roots were present with water stress, and thicker ones in substrates near field capacity, except in the segment where the radial root growth was not affected by the substrate Ψw..In general, root tissues grew coordinately and córtex cells showed the greatest radial growth, which contributed more to the increase in the total root diameter. Nevertheless, córtex cells also showed a greater expansion lengthwise. On the other hand, the concentration of proline in the tissues of the apical zone was consistent with the idea that proline has a roll in the osmotic adjustment, as a cytoplasm solute, to maintain growth with low Ψw in the substrate. The concentration of soluble protein was greater in the apical zone than in the middle zone of the root, but only in substrates with low Ψw. It was conclude that the root of tepary bean seedlings survives and maintains growth in substrates with low Ψw because its apical zone has a dynamic and physiologically complex growth as a response to water stress

Présentation

Version intégrale (7,45 Mb)