Moacyr Eurípedes Medri

Anatomia ecológica de Sebastiania commersoniana (Baillon) Smith & Downs (Euphorbiaceae) submetida ao alagamento

In the woods along the Tibagi River hydrographical basin, in areas subject to periodical flooding, the incidence of S. commersoniana is usual, it often becoming the prevailing species. Plants of this species were kept in well drained and flooded soils for two months, in order to explain some aspects of tolerance to waterlogging. After this period, some plants were returned to the well drained soil in order to check the species behaviour in the re-aeration period. In the roots, flooding induced, an increase of intercellular spaces as well as a thickening of the cortex, and a reduction in the thickeness of the central cylinder. Flooded plants grew less than the control ones, and developed hypertrophic lenticels and some adventitious roots. The re-aired plants recovered in growth. It can be suggested that the morphoanatomical modifications observed are important to explain the tolerance of this species to flooding, if we take into consideration the obtained results, together with those obtained in the literature about floristic and phytosociology, as well as in that dealing with biochemistry.

Photosynthesis, growth and development of Tabebuia avellanedae Lor. ex Griseb. (Bignoniaceae) in flooded soil

Foram estudadas as modificacoes morfo-anatomicas e ecofisiologicas que o alagamento provoca em Tabebuia avellanedae Lor. ex Griseb. (Bignoniaceae), correlacionando-as com sua capacidade de tolerar o excesso de agua no solo. Plantas com tres meses de idade, crescendo em casa de vegetacao, foram submetidas a 56 dias de alagamento e a um periodo de pos-alagamento. A taxa fotossintetica e o crescimento de T. avellanedae decresceram conforme aumentou o tempo de alagamento, mas mesmo nao sendo altamente tolerante, a especie foi capaz de se adaptar a curtos periodos de alagamento. Esta relativa tolerância provavelmente se deve a capacidade apresentada por T. avellanedae de desenvolver estruturas que amenizam os efeitos do alagamento, promovendo a difusao interna de oxigenio da parte aerea para as raizes, tais como rachaduras caulinares, raizes superficiais e lenticelas hipertrofiadas nas raizes. Como nao houve acentuada variacao na anatomia interna de folhas e raizes de T. avellanedae, alteracoes metabolicas provavelmente auxiliaram na sobrevivencia da especie durante o alagamento.

Modifications on leaf anatomy of Coffea arabica caused by shade of pigeonpea (Cajanus cajan)

Adaptacoes de plantas da mesma especie aos diferentes habitats, constituem a base da diferenciacao entre folhas a pleno sol e folhas sob sombra e estao associadas a caracteristicas anatomicas distintas. Para caracterizar tais mudancas em cafeeiros cultivados sob sombra de guandu (Cajanus cajan) e a pleno sol, em Londrina, PR, foram realizadas avaliacoes de modificacoes ocorridas na anatomia foliar. As estruturas internas avaliadas foram: parede celular e cuticula; epiderme; mesofilo (parenquima palicadico, parenquima lacunoso e espacos intercelulares) e estomatos. Para todas as variaveis avaliadas observaram-se diferencas anatomicas entre folhas expostas ao sol e a sombra. As folhas expostas ao sol apresentaram cuticulas e paredes celulares mais espessas, celulas da epiderme mais estreitas, parenquima palicadico com celulas mais alongadas, parenquima lacunoso espesso e com poucos espacos intercelulares e maior numero de estomatos. Folhas sob condicoes de denso sombreamento apresentam menor espessamento da cuticula e da parede celular; mesofilos com menores volumes, porem com maiores espacos intercelulares; epidermes com celulas mais espessas e estomatos em menor quantidade, envoltos por celulas subsidiarias de menores dimensoes. Plantas cultivadas a pleno sol apresentam maiores taxas fotossinteticas. Assim, Coffea arabica caracteriza-se como uma especie com grande amplitude de adaptacao fenotipica as mudancas na intensidade de radiacao solar.

ADAPTATIONS TO FLOODING BY TROPICAL TREES: MORPHOLOGICAL AND ANATOMICAL MODIFICATIONS

Many plant communities subjected to flooding are found in tropical regions and are rich in tree species. Little is known about the flood-tolerance mechanisms these species have developed. However, studies have shown that metabolic, morphological and anatomical adaptations are all important for the survival of these plants in oxygen-deficient conditions. Lenticels hypertrophy, aerenchyma formation, stem hypertrophy and the formation of adventitious roots are among the morphological and anatomical adaptations caused by flooding. These modifications enhance the oxygenization of submerged roots, permitting sufficient energy production for survival. Ethylene, which increases markedly in flooded plants, seems to be the main hormone involved in bringing about these morphological modifications. In the case of the initiation and development of adventitious roots there is a synergism between ethylene and auxin. Broader studies are now necessary to improve the understanding of these questions because of the complexity of the responses of tropical tree species to flooding.

Soybean physiology and gene expression during drought.

Soybean genotypes MG/BR46 (Conquista) and BR16, drought-tolerant and -sensitive, respectively, were compared in terms of morphophysiological and gene-expression responses to water stress during two stages of development. Gene-expression analysis showed differential responses in Gmdreb1a and Gmpip1b mRNA expression within 30 days of water-deficit initiation in MG/BR46 (Conquista) plants. Within 45 days of initiating stress, Gmp5cs and Gmpip1b had relatively higher expression. Initially, BR16 showed increased expression only for Gmdreb1a, and later (45 days) for Gmp5cs, Gmdefensin and Gmpip1b. Only BR16 presented down-regulated expression of genes, such as Gmp5cs and Gmpip1b, 30 days after the onset of moisture stress, and Gmgols after 45 days of stress. The faster perception of water stress in MG/BR46 (Conquista) and the better maintenance of up-regulated gene expression than in the sensitive BR16 genotype imply mechanisms by which the former is better adapted to tolerate moisture deficiency.

Flooding tolerance and genetic diversity in populations of Luehea divaricata

We investigated some aspects of flooding tolerance in two riparian populations (exposed and no exposed to flooding) of Luehea divaricata C. Martius. Plants derived from seeds collected in each population were submitted to flooding (30 and 60 d), submergence and re-aeration treatments. Plants exposed to flooding showed development of aerenchyma, hypertrophic lenticels and new adventitious roots. Interestingly, whereas the plants originated from population naturally exposed to flooding developed some of these alterations more markedly, they could not survive when totally submerged. The random amplified polymorphic DNA (RAPD) markers, showed a significant difference between populations, suggesting that seasonal flooding on riparian populations of L. divaricata has been selecting individuals who are more adapted to survive in these conditions.

Aspectos morfo-anatômicos e fisiológicos de Peltophorum dubium (Spr.) Taub. submetida ao alagamento e à aplicação de etrel

The effects of flooding and ethrel application on P. dubium for a 70-day period were studied in order to elucidate the aspects of plants tolerance to hypoxia. During the experiment the thickness of the stem base, and the allocation of dry matter for the roots, stems and leaves were evaluated. Flooding increased both the thickness of the stem base as well as a great hypertrophy of the lenticels. The ethrel application did not induce the formation of adventitious roots, but it stimulated the hypertrophy of lenticels. The flooding and/or ethrel application significantly affected the growth and development of the plants. This effect was greater in the flooded plants which had their lenticels sealed. The results show that P. dubium can tolerate periods of flooding, possibly because of the morpho-anatomic modifications induced by variations in the hormone levels, led by ethylene.

Metabolismo respiratório de raízes de espécies arbóreas tropicais submetidas à inundação

Aiming at elucidating certain aspects of the respiratory metabolism of roots of flood-tolerant tropical tree species (Lonchocarpus muehlbergianus, Sebastiania commersoniana and Sesbania virgata) as well as flood-intolerant species (Peltophorum dubium and Schinus terebinthifolius), plants were submitted to 2, 10 and 60 days of flooding. After these periods, the absorption of O2 and liberation of CO2 by the roots were determined. The respiratory metabolism of the roots of tolerant species presented a drop due to flooding. Only S. commersoniana presented a recovery in respiration after 60 days of flooding. The intolerant species S. terebinthifolius did not present alterations caused by flooding in its aerobic metabolism, whereas P. dubium, also intolerant, presented a drop in the absortion of O2 with two days of hypoxia, and recovery after 60 days. The liberation of CO2 in the tolerant species followed the same pattern of O2 absorption, with the exception of S. commersoniana, which presented a reduction in the liberation of CO2 after 60 days of flooding similar to what happened to P. dubium. In S. terebinthifolius there was no significant reduction with flooding. The difficulty in establishing a difference pattern in the respiratory metabolism of the species studied, concerning tolerance to flooding, emphasizes the complexity of tropical plant responses.

Physiological aspects of sun and shade leaves of Lithraea molleoides (Vell.) Engl. (Anacardiaceae)

O presente trabalho teve como objetivo avaliar de forma comparativa alguns parâmetros fisiologicos de folhas de sol e de sombra de um especime de L. molleoides. Esta especie e conhecida popularmente como aroeira-branca. As folhas da porcao superior periferica, denominadas folhas de sol, apresentaram igual taxa fotossintetica, menores teores de clorofilas (a, b e totais), mesma razao clorofila a/ clorofila b, menor taxa transpiratoria, mesma condutância estomatica e concentracao intercelular de CO2 em relacao as folhas da porcao inferior interna, denominadas folhas de sombra. A concentracao de nutrientes, excetuando Ca e Mg, foi igual em folhas de sol e de sombra. As respostas dos parâmetros fisiologicos avaliados indicam que as folhas de sombra, apesar de receberem menor intensidade luminosa, tem possibilidade de crescer e se desenvolver com a mesma capacidade das folhas de sol.

Cloning and quantitative expression analysis of drought-induced genes in soybean.

We determined the expression levels of DREB transcription factor (Gmdreb1) and of the genes Gmgols, Gmpip1b, Gmereb, and Gmdefensin in drought-tolerant (MG/BR46-Conquista) and drought-sensitive (BR16) genotypes of soybean, during drought. The trial was carried out in a controlled-environment chamber, set up to provide drought conditions. Sequences of Arabidopsis thaliana DREB-family proteins were used to build a phylogenetic tree through the alignment of the conserved regions near the AP2 domain. We found that Gmdreb1 is similar to Atrap2.1, which is located near the AtDREB1 and AtDREB2 families. The amplified fragment was cloned and sequenced; alignment with the sequence available at Genbank showed total similarity. Expression analysis showed that under drought: a) Gmdreb1 expression increased in leaves and roots of both genotypes and expression level changes occurred that were correlated with the length of the water-deficit period; b) there were increased expression levels of Gmdefensin in roots of MG/BR46; c) expression of Gmgols increased in leaves and roots of the two genotypes; d) Gmpip1b expression generally increased, except in roots of BR16, and e) the same was found for Gmereb, except in roots of MG/BR46.