Data/hora: 27/05/2024 02:07:59

Biblioteca(s): | Embrapa Florestas.
Data corrente: | 06/06/1995
Data da última atualização: | 18/03/2009
Autoria: | BRUNE, A.
Título: | Physiology of flowering in Cupressus arizonica greene seedlings.
Ano de publicação: | 1973
Fonte/Imprenta: | 1973.
Páginas: | 64 f.
Idioma: | Inglês
Notas: | Dissertation (Doctor of Philosophy) - Graduate Council, University of Florida, Florida.
Conteúdo: | Very little is known about physiological changes occurring within a plant during transition to flowering. This work was undertaken in an attempt to learn more about floral induction and to peprfect some techniques with the plant, Cupressus arizonica, which readily responds to chemical treatment of Ga by producing strobili. Conclusions which can be drawn from the present study are: 1. GA3 induces both vegetative and reproductive growth of Cumpressus arizonica. Seedling response is varied; some produce strobili profusely, others scarcely and somenone at all. This suggests that genetic material highly responsive to GA, or nonresponsive, can be clonally propagated and offers better future experimental material. 2. Complete fertilizer or urea application enhances response to GA3 however, the combination of GA and high concentration of urea, is toxic to some Curpressus plants, but those which survive grow considerably taller, and produce both more megasporangiate stribili and more microsporangiate strobili than any other combination of urea, GA and auxin. Presumably an auxin is involved in regulating reproductive development of growth of megasporangiate strobili. The effective concentration of auxin may be different from the one used here. It can be speculated that absorption of hormones through the outer leaves is different from plant to plant, corresponding to the variation in their phenotypic appearance, which shows a remarkable range in color and shape. A preliminary experiment with a limited number of seedlings showed that injection of GA3 is very efficient to insure uptake. 3. Short photoperiodsand application of high GA concentrations are conducive to a higher ratio of megasporangiate strobili to microsporangiate strobili than long photoperiods and applications of low GA concentrations. 4. An efficient method was developed to seletively produce either largely megasporangiate strobili or mirCumpressus arizonica seedlings: applications of GA to the top part of a plant result mainly in production of megasporangiate strobili; whereas, GA applications to the lower branches result almost exclusively in microsporangiate stobili being induced. This is in accord with the view that the control of the kind of strobili produced is dependent on a stimulus and the nutritional status of the plant part where strobili will be initiated. The flowering stimulus has a marked tendency to move upwards. This tendency, and the difefrence of response of applications to the lower and upper part of plants, result in the top of the plant producing megasporangiate if GA is applied to the top, but microsporangiate if application is the lower parts. Thus, the upper branches respond differently depending on where the stimulus was first applied. Considering studies of GA movement in other plants, it is possible to link this difference in response to nutrient contents: GA applied to the lower parts drains carbohydrates down from the top resulting in the production of microsporangiate strobili on the uupper branches; GA applied tothe top moves carbohydrates up, and megasporangiate strobili are produced. This hypothesis can casily by tested following movement of 3h labelled GA and 14C'labelled carbohydrates and content in the plant. 5. Enzyme extration and detection in Cupressus arizonicz tis tues works well, providing relatively large amoiunts of plant material are available. But this is a handicap in detecting enzyme changes in the actual microscopical amounts of tissues where induction and transition to flower bud occurs. Improvements can probably de made in the techniques applied to micro amounts of protein. 6. Genetically homogenous material would be preferable to the variable source material used in these studies. The large range of variation among Cupressus arizonica seedlings is a disadvantage in physiological-biochemical studies. Clones can be established for uniformity. In this aspect Cryptomeria japonica may be more useful. It a commercially more important species, is easily propagated vegetatively, and has larger buds. Cryptomeria japonica also prodeces strobili after GA treatment.
Thesagro: | Fisiologia.
Thesaurus Nal: | Cupressus arizonica; plant physiology.
Categoria do assunto: | --
Registro original: | Embrapa Florestas (CNPF)
Exemplares: | CNPF - (29764-1) - ADC - TS - -- - TS0074 -  - TS0074 - DIS