Estrategias adptativas de especies arboreas tipicas de ambiente do solo hidricamente saturado : uma abordagem morfologica, bioquimica e ecofisiologica

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

The hydric saturation of soil leads to a rapid 02 depletion, that limits processes as germination, establishment and plant growth. The goals of the present thesis were to characterize demographic aspects, to identify the adaptative responses of seeds and plants of five tree species that enable their development on the swampy forest, and to correlate these responses with the species abundance. In a O,3ha. plot of flooded - forest of Reserva de Santa Genebra, 1853 plants of Tapírira guíanensís (Anacardiaceae), 287 of Protíum heptaphy/lum (Burseraceae), 155 of Talauma ovata (Magnoliaceae), 83 of Cariníana estrelensís (Lecythidaceae) and 52 of Pseudobombax grandíflorum (Bombacaceae) were marked, and the five species showed an aggregated distribution- T. guíanensís, P. heptaphyllum and T. ovata populations showed a predominance of seedlings and saplings whereas the populations of C. estrelensís and P. grandíflorum showed a great number of adult trees. The fruit output was not regular for all species what resulted in differents patterns of natality, and the death rate was predominant on the smaller size classes. T. guíanensís e P. heptaphyllum fruit on an irregular pattern, but the great quantity of fruits produced during the rainy season leads to the establishment of a flooding tolerant seedling carpet. The other three species disperse their seeds during the dry season. Though T. ovata produces fruits every year, its recruitment is not massive. C. estrelensís and P. grandíflorum showed an irregular fruit output without recruitment. No one of the species was able to germinate when submersed but the seeds kept their viability for a long time (several days) under hypoxic and anoxic conditions. The ethanol was the main product of anaerobic metabolism accumulated on the seeds, but C. estrelensís and P. grandíflorum also accumulated lactate. Hypoxic and anoxic conditions did not induce the malate production. The experimental flooding at a green house did not reduce the plant growth. The five species showed lenticels hypertrophy after a week of flooding, and the new roots induced by flooding were much more aerenchymatosous than the original ones. Greats quantities of ethanol and lactate accumulated an the flooded root system of T. guíanensís and P. heptaphyllum, which were degenerated and replaced by new roots. The root system of T. guíanensís was substituted by the adventitious roots growth, which were more porouses and also showed a distinguished metabolic activity. Besides the adventitious roots P. heptaphyllum also showed growth of regenerant roots, that is, development of new roots after flooding, from the main root or as branches of secondaries ones. The flooded root system of T. ovata plants was not compromised, and although ethanol was the main product of metabolism, its accumulation was smaller than on the other species and the lactate accumulation was only temporary. The flooding also induced new roots formation, much more aerenchymatous, and very different from the originals. These were whiter, without ramification, growing near at the soil surface. Nevertheless, the death of the root system of C. estrelensís and P. grandiflorum was not followed by the growth of numerous roots as it did on the other species, remaining a few live roots after 60 days of flooding. The hypoxic conditions on the root system led to partial reduction of CO2 assimilation and stomatal conductance, followed by recovery signs during the flooding treatment. The quantum yield of photosystem II (Fv/Fm) was not modified on the leaves of flooded plants except by a light reduction on P. grandiflorum. Nevertheless, the new leaves of C. estrelensís, expanded during the flood, were the unique to show values of Fv/Fm smaller than the control ones. In fact, the occurrence of these species on flooded forests is due to phenologic strategies, metabolic and morpho-anatomic responses which make possible partial root aeration. These feactures provide the metabolic control that enable the plant growth under hypoxic conditions

ASSUNTO(S)

germinação demografia fotossintese

ACESSO AO ARTIGO

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