Le gel est un des facteurs majeurs limitant l’aire de répartition des végétaux. Il a pour conséquence de limiter l’efficience de la circulation de sève brute par formation d’embolie dans les vaisseaux du xylème. Lorsqu’il y a formation de glace dans les tissus, les cellules vivantes peuvent également être lysées dans les organes lignifiés, et dans les bourgeons. Pour pallier cela, différents mécanismes de résistance sont développés pour limiter la formation d’embolie ou la résorber, pour augmenter transitoirement la tolérance à la formation de glace dans les tissus et pour éviter d’exposer les bourgeons et jeunes feuilles aux gels printaniers tardifs. Ces différents traits ont été caractérisés pour onze espèces communes ayant des limites altitudinales potentielles contrastées. Puis la physiologie de l’acclimatation au gel chez Juglans regia L. a été caractérisée, essentiellement à travers les relations entre humidité pondérale, contenu en sucres solubles, climat et levée de dormance. L’ensemble de ces données a permis d’élaborer un modèle prédictif de la résistance au gel en relation avec la physiologie de l’arbre qui pourrait, couplé avec d’autres modèles simulant la période estivale, permettre d’estimer la conjonction de différents stress sur le potentiel de résistance. / Frost is one of the major limiting constraints for plants causing embolism, living cell lysis and damages on buds during spring. Several processes are observed in trees in order to limit embolism or refill vessels, to increase frost resistance and to avoid freezing period for buds while bursting. Those different processes were monitored in eleven common species according to their potential alitudinal limt. And one was selected (Juglans regia L.) and physiology of acclimation was caracterised through interaction between water content, soluble carbohydrate (which are the best explaining factors for frost resistance), climate and dormancy release. According to those data, a predicting model for frost hardiness was built related to physiology of acclimation. This kind of model would be usefull related to a summer simulating model in order to estimate interaction between different stresses for frost hardiness potential.

Made available in DSpace on 2016-12-08T16:44:34Z (GMT). No. of bitstreams: 1 PGPV09MA042.pdf: 353135 bytes, checksum: f6e276c764d17f2d788c1c6b5cd1e088 (MD5) Previous issue date: 2009-02-05 / The objective of this study was to evaluate the tolerance of Eucalyptus dunnii Maiden, E. benthamii Maiden & Cambage, E. grandis W. Hill ex Maiden e E. saligna Sm., to low temperature (LT&#8325;&#8320;) of seedings when submitted to diferente rustification periods, using as cold tolerance indicators the contentes of total soluble carbohydrates and proline in the leaves. The work was carried out in the Plant Physiology Laboratory of the Agricultural and Veterinary Sciences Center of the University of Santa Catarona State UDESC. Two experiments were performed using a randomized block design. On the first experimente, (clone K-1007) Eucalyptus dunnii seedlings were submitted to diferente periods rustification (0,7,21 and 42 days) and after each rustification period, the seedling were exposed to diferente sub-zero temperatures (-2°, -4°, -6° and -8°C). On the second experimente, seedlings of species Eucalyprtus dunnii (clone KF 09), E. benthamii (clone ARV 116), E. grandis (clone 360 ) and E. saligna (clone 2864) were submitted to two rustification periods (0 and 21 days) and after each rustification period, the seedlings were exposed to three sub-zero temperatures (-2°, -5° and -8°C). In the both experiments the rustification was performed under a regime of daily and night temperatures of 1°C and 5°C, respectively, with photoperiod of 12h. were evaluated the concentrations of total soluble carvohydrates and proline in the leaves, the LT&#8325;&#8320;, the electric conductivity, and the damage index. The data were submitted to analysis of variance followed by the linear regression analysis, Pearson s correlation and in the experimente 2, as well as, to the Test of Tukey (p<0.05). the data obtained on the first experimente with E. dunnii, showed na invrease in the tolerance of this species to low temperatures with increase of leaf contentes of total soluble carbohydrates when submittedmto a rustification period up to 35 days. It was also observed that there is a relationship between the cold tolerance and the increase of leaf total soluble carbohydrates. On the second experimente, diferences were observed between the species regarding to the cold tolerance. The E. dunnii and E. benthamii presented a higher cold tolerance followed by the E. saligna and E. grandis. However, in all the species studied, it was observed a good relationship between to cold tolertance (lower LT&#8325;&#8320;) with the rustification period and that tolerance was correlated to the increase in the leaf contentes of total soluble carbohydrates. The presence of proline in the leaf tissues was found only in the plants of E. dunnii on first experimente and there was no increase within the rustification period. In both experiments it was not observed any relationship between the leaf proline contente and cold tolerance. It was concluded that the increase of cold tolerance of eucalyptus species, in response to low temperature of the plants, was mostrly due to the increase of total soluble carbohydrates in leaf contentes, rather than to the leaf proline contents / Objetivou-se com este trabalho avaliar a tolerância à baixa temperatura (LT50) em mudas das espécies de Eucalyptus dunnii Maiden, E. benthamii Maiden & Cambage, E. grandis W. Hill ex Maiden e E. saligna Sm., submetidas a diferentes períodos de rustificação, usando como indicadores de tolerância ao frio os teores foliares de carboidratos solúveis totais e prolina. Foram realizados dois experimentos, usando-se o delineamento experimental blocos ao acaso, no Laboratório de Fisiologia Vegetal do Centro de Ciências Agroveterinárias da Universidade do Estado de Santa Catarina UDESC. No primeiro experimento, mudas de Eucalyptus dunnii (clone K-1007) foram submetidas a diferentes períodos de rustificação (0, 7, 21 e 42 dias) e após cada período de rustificação as mudas foram expostas a quatro gradientes de temperatura negativa (-2,-4,-6 e -8ºC). No segundo experimento, mudas das espécies de E. dunnii (clone KF 09), E. benthamii (clone ARV 116), E. grandis (clone 360) e E. saligna (clone 2864) foram submetidos a dois períodos de rustificação (0 e 21 dias), sendo que após cada período de rustificação as mudas foram expostas a três gradientes de temperatura negativa (-2,-5 e -8ºC). Em ambos os experimentos a rustificação foi realizada sob um regime de temperaturas diurnas e noturnas de 1ºC e 5ºC, respectivamente, com fotoperíodo de 12 horas. Foram avaliadas as concentrações foliares de carboidratos solúveis totais e de prolina, o LT50, através da condutividade elétrica, e o índice de dano. Os dados foram submetidos à análise da variância e após a análise de regressão linear, teste de correlação de Pearson e, no experimento 2, também ao teste de Tukey (p<0,05). Os dados obtidos no primeiro experimento, com E. dunnii, demonstram que ocorreu um aumento na tolerância desta espécie a baixas temperaturas observando-se um incremento nos teores foliares de carboidratos solúveis totais até 35 dias de rustificação. Também foi observado que existe uma relação entre a tolerância ao frio e o incremento nos teores foliares de carboidratos solúveis totais. No segundo experimento, houve diferenças entre espécies quanto à tolerância ao frio, sendo que as espécies E. dunnii e E. benthamii apresentaram maior tolerância ao frio seguido das espécies E. saligna e E. grandis. No entanto, em todas as espécies estudadas foi observada uma maior tolerância ao frio (menor LT50) das plantas submetidas à rustificação e que esta tolerância está associada ao incremento nos teores foliares de carboidratos solúveis totais. A presença de prolina nos tecidos foliares foi identificada apenas nas plantas de E. dunnii do primeiro experimento e não houve alteração na concentração com o aumento do período de rustificação. Em ambos os experimentos não foi observada correlação entre os teores foliaresde prolina com a tolerância ao frio. Conclui- e que o aumento da tolerância ao frio de espécies de Eucalyptus, em resposta à rustificação das plantas, deve-se em grande parte ao incremento nos teores foliares de carboidratos solúveis totais e não aos teores foliares de prolina

Dissolved oxygen (DO) level is a critical factor for the survival of fishes and sustainable management of an aquatic ecosystem. This study aims to investigate the lethal thresholds of three major fish species in the Love River, Kaohsiung, S. W. Taiwan, in an attempt to provide ecological points of view for the further improvement of the river-water quality, as well as for the restoration of its fish community. Laboratory tolerance experiments of fish fries, including mullet (Liza macrolepis), milkfish (Chanos chanos) and tilapia (Oreochromis mossambicus), exposed to low levels of dissolved oxygen were conducted in the period of January 2002 to April 2003. At water temperature of 23¢J, median lethal times (LT50) and 48 hours median lethal concentrations (48h LC50) at the salinity of 10‰, 20‰ and 30‰ were determined, respectively. We also carried out a lethal DO experiment to mullet fry in a sudden drop of salinity from 30‰ to 20‰, which is always the case when the sewage gate of the Love River interception system is opened to avoid flooding after heavy rainfall. Under the condition of 20‰ salinity, the tolerance of low dissolved oxygen for the three species of fish fries were significantly different. Among them, milkfish was found to be the most sensitive species, followed by mullet, whereas tilapia was the most tolerant species. The 48h LC50s of milkfish, mullet and tilapia were 15.7, 8.6 and 7.8% air saturation, respectively, which were 1.16, 0.63 and 0.57 mg/l at 23¢J. Similarly, the LT50s also showed species-specific differences. At DO level of 0.52 mg/l, the LT50s were 77.9 minutes for milkfish, 245.7 minutes for mullet and over 1000 minutes for tilapia. The changing of salinity affecting the tolerance of low dissolved oxygen in fish fries was species depending. The DO lethal concentrations of mullet fry increased with the decrease of salinity, but not the case for milkfish fries. The 48h LC50 of mullet fries in 30‰ saline water was 11.5% air saturation (0.8 mg/l), which was higher than those in 10‰ and 20‰ saline water. However, no significant difference in 48h LC50 was found between milkfish kept in 10‰ and 20‰ saline water. The 48h LC50 for the former was 14.9% air saturation while the latter was 15.7%. Both are equivalent to 1.16 mg/l at water temperature of 23¢J. A rapid change of salinity reduced the low Do tolerance of fish fry. When mullet fry were introduced to 20‰ saline water from acclimated salinity of 30‰, its 48h LC50 raised significantly (13.9% air saturation; 1.02 mg/l). Under the DO concentration of 0.52 mg/l, the LT50 also dropped to 7.6 minute. It means that the opening of sewage interception gate largely challenges the survival fish fry. Based on the results of current study, the DO level of Love River is suggested to be maintained beyond 2.19 mg/l (28 % air saturation, 48h LC50 of milkfish at 10‰ salinity and 23¢J water temperature), in order to achieve a sustainable environment for the present fish community. In case of that DO occasionally fall to the above level, it is strongly recommended that a manual aeration system should be operated within 100 minutes.

No description available.

Le gel est un des facteurs majeurs limitant l'aire de répartition des végétaux. Il a pour conséquence de limiter l'efficience de la circulation de sève brute par formation d'embolie dans les vaisseaux du xylème. Lorsqu'il y a formation de glace dans les tissus, les cellules vivantes peuvent également être lysées dans les organes lignifiés, et dans les bourgeons. Pour pallier cela, différents mécanismes de résistance sont développés pour limiter la formation d'embolie ou la résorber, pour augmenter transitoirement la tolérance à la formation de glace dans les tissus et pour éviter d'exposer les bourgeons et jeunes feuilles aux gels printaniers tardifs. Ces différents traits ont été caractérisés pour onze espèces communes ayant des limites altitudinales potentielles contrastées. Puis la physiologie de l'acclimatation au gel chez Juglans regia L. a été caractérisée, essentiellement à travers les relations entre humidité pondérale, contenu en sucres solubles, climat et levée de dormance. L'ensemble de ces données a permis d'élaborer un modèle prédictif de la résistance au gel en relation avec la physiologie de l'arbre qui pourrait, couplé avec d'autres modèles simulant la période estivale, permettre d'estimer la conjonction de différents stress sur le potentiel de résistance.

No description available.