Physiologische Anpassungsmechanismen an an miedrige temperaturen bei. Leycopersicon esculentum MILL
Abscisic acid (ABA) is supposed to play an important role during the acclimation of plants to abverse environmental conditions. The purpose of this paper is to shed more light on this complex process, considering the influence of environmental conditions accompanying hardening, especially temperatur...
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- Formato:
- Tesis Libro
- Lenguaje:
- inglés
- Publicado:
-
Hamburg
Universitat
1991
- Colección:
- Dissertation: Zur Erlangung des Doktorgrades des Fachbereichs Biologie
Literaturverzeichnis: S: 83-97
nº de orden interno: TDB-12 - Materias:
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| Sumario: | Abscisic acid (ABA) is supposed to play an important role during the acclimation of plants to abverse environmental conditions. The purpose of this paper is to shed more light on this complex process, considering the influence of environmental conditions accompanying hardening, especially temperature rhythms and relative humidity, on abscisic acid levels and the possible involvement of the hormone in the different adaptative responses.- Different physiological parameters (dry and fresh weight, relative growth rate, plastochrom index, leaf area increase, water potential, osmotic potential, abscisic acid content, proline content, stomatal resistance, phospholipid content and composition, and 14C -choline incorporation into phosphatidylcholine) were investigated during the acclimation of tomato plants to low temperatures. Similar studies were carried out on plants treated with the synthetic abscisis acid-analogue LAB144143 applied to the leaves and choline chloride applied through the soil. Tomato plants (Lycopersicon esculentum Mill., cv. Hellfrucht Frühstamm) were acclimated for 5 days at 15º C/5ºc and 25ºC/5ºC (day/night), and two relative humidity (RH) levels (100 p/ciento, 80 p/ciento) during the cold nights. The role of root temperature was also investigated keeping the roots al 20ºC. Limited hardenings experiments were also perfomed with the "flacca" mutant form of tomato cv. Ailsa Craig. The control and chemical-treated plants were maintained at 25ºC/15ºC and 80 p/ciento RH.- After accilation the plants were submitted to chilling (3ºC, 80 p/ciento RH, 24-48 h) and frost (-2ºC, 2h) tests. Following these tests the effectiveness of the different hardening treatments was estimated determining the necrosed leaf area and measuring CO2 - and H2O-exchange.- No turgor or water potential decrease were detected during the hardening period or chemical treatment. Moreover, at the end of this phase turgor and water potential level were always higher. But ABA increases were observed at 80 p/ciento RH in the two temperature regimes, suggesting that transient and localized changes in the water relations during the cold nights trigger ABA production. Acclimation at 80 p/ciento RH induced a significant increase of ABA concentration which affected stomatal behaviour and proline levels. Acclimation at 100 p/ciento RH had no effect on ABA levels or stomatal behaviour, with limited or no increase on proline concentration. All acclimation and chemical treatments stimulated the incorporation or 14C-choline into phosphatidylcholine and showed an increased total phospholipid level.- Acclimation at 80 p/ciento RH resulted in a rather efficient protection against chilling induced water stress. Only a reduced, though significant increase in chilling tolerance was observed after acclimation at 100 p/ciento RH or chemical treatments. On the other hand, acclimation al 100 p/ciento RH was as effective as acclimation at 80 p/ciento RH in increasin frost tolerance. Flacca tomato was also able to some degree to acclimate against chilling.- The results indicate that ABA increase during acclimation at low relative humidity is essential against chill-induced water stress, improving stomatal and root function at low temperature, and promoting proline and phospholipid synthesis. On the other hand, the improvement of chillind and frost tolerance without changes in ABA levels and that the ABA-deficient flacca-mutant can achieve a certain hardening degree sugest that at least some hardening events (such as increased phospholipid level, reduced cell size and water content) may be induced without ABA participation. Defferent hypotheses could be proposed to explain these results: a) there is a change in the ABA-sensitivity in acclimated tissues. b) low temperature induces ABA redistribution in different cell compartments, which triggers acclimation. c) other changes in the hormonal balance at low temperature, such as gibberellin and/or cytokinin decrease, facilitates ABA action without increase of its absolute level. d) some hardening events may be triggered by temperature alone, as in other non-plant organisms.- LAB144143 applied at non-hardening temperatures is efficient against chill-induced water stress, but almost ineffective against light frost, suggestin that other factors diferent from ABA are also very important during acclimation, and must be considered in order to develop chemical hardening procedures.- |
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| Descripción Física: | 99 p. il. ; 20,5 cm. |