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Accueil du site → Doctorat → Grèce → Αξιολόγηση του παραγωγικού δυναμικού και της αισθητικής αξίας του Lotus corniculatus L. για αναβάθμιση του λιβαδικού τοπίου

Aristotle University of Thessaloniki (AUTH) (2003)

Αξιολόγηση του παραγωγικού δυναμικού και της αισθητικής αξίας του Lotus corniculatus L. για αναβάθμιση του λιβαδικού τοπίου

Μωρίδου Δήμητρα

Titre : Αξιολόγηση του παραγωγικού δυναμικού και της αισθητικής αξίας του Lotus corniculatus L. για αναβάθμιση του λιβαδικού τοπίου

Auteur : Μωρίδου Δήμητρα

Grade : Doctor of Philosophy (PhD) 2003

Université de soutenance : Aristotle University of Thessaloniki (AUTH)

Résumé
Grazing and drought are two very important factors in the last decades, because the climatic conditions had changed, especially in Meditterannean zone and drought is increased and the production is reduced ; while the intensity of grazing is increased as well. Lotus corniculatus L., one of the most desirable plant for the pastures, is considered as a “cosmopolitan“ plant with wide ecological spectrum as well as a drought resistant plant participating at high percentage in rangelands. This ecological behavior of Lotus corniculatus L., suggests a phenotypic plasticity which arises a very high researching interest. That is why the aims of this thesis were : 1) The study of the plant’s ecophysiological mechanisms which work under the theory of “sink - source“ 2) Whether these mechanisms affected the productivity of the pastures under the synergy of grazing and drought. 3) Approaching the aesthetic value of Lotus corniculatus L. as a component of the pastures. For the realization of the previous “aims“, plants of Lotus corniculatus L were sowed in giffy - pots and were transplanted in 24,5 L pots in order to obtain the same leaf area in every pot. The statistic plan in the field was the randomized block with two factors : a) Water at two levels : “in water“ plants W, “in rain“ plants R, b) Grazing (cutting) at four levels : [(1ο level, C0, cutting in July), (2ο level, C1, cutting in May), (3ο level, C2, cutting May and June), (4ο level, C3, cutting in May, June and July)]. The experiment had the following treatments : C0W, C1W, C2W, C3W, C0R, C1R, C2R, C3R. Leaf area index, weight of leaf, weight of the upper part of the plant, specific leaf area, specific leaf weight, leaf area ratio and drought production coefficient were measured and calculated. Also, leaf water potential, osmotic potential, turgor, relative water content and stomatal conductance were measured and calculated. The results showed that in the plants of C3R treatment, weight and leaf area were higher than those of the plants of C3W treatment, a fact that suggested that the frequent cutting, combined with drought, affected the polarised system “sink - source“ in Lotus corniculatus L. resulting in the remaining of photosynthesis products at the leaves. Thus, the leaf area was increased, implying at the same time an increase of drought production coefficient. This unexpected behavior of C3R treatment of Lotus corniculatus L. would be contributed to hydrodynamic plasticity. Indeed, both treatments C3R and C3W, changed the osmotic potential and the turgor, in relation to relative water content, with the same way, a fact not observed in the other treatments. Furthermore, the turgor maintainance, due to high difference, between water potential and osmotic potential changes, seemed to be holded at the same level in C3R and C3W treatments. The arised question is whether the mechanism of osmotic adjustment or/and the module elasticity of cell wall intervenes to high turgor maintainance. The results suggested that the mechanism of osmotic adjustment seemed to have very small contribution to turgor maintainance in C3R treatment. Converselly, the module elasticity mechanism, seemed to be the only mechanism which affected the turgor. In the other treatments, the most important intervened mechanism was mainly the osmotic adjustment. It is evindent, that the frequent cutting changed the intervened mechanism of turgor maintainance from osmotic adjustment to module elasticity. On the other hand, this turgor maintainance resulted in high stomatal conductance, followed by high photosynthetic efficiency and finally by increased production. Indeed, the stomatal conductance in C1R and C2R treatments remained at high values, because of the mechanism of osmotic adjustment, though in C3R treatment the high value of stomatal conductance was due to module elasticity. Leaf area ratio might be used as an index of “ocular” quality or aesthetic value of a pasture and the base of the ecological value of grasses for restoration, reclamation of pastures.

Mots clés : Lotus corniculatus L. ; Cosmopolitan plant ; Drought ; Grazing ; Aesthetic value ; Production ; Restoration ; Reclamation ; Pastures ; Langue : grec

Présentation (National Archive of PhD)

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