Fernando Henrique Aguiar Vale

The influence of light intensity on anatomical structure and pigment contents of Tradescantia pallida (Rose) Hunt. cv. purpurea Boom (Commelinaceae) leaves

The aim of this work was to study the effects of five different light intensities on the anatomical structure and on the pigment contents in leaves of Tradescantia pallida cv. purpurea. Once light intensity became lower, the thickness of leaf lamina and mesophyll were reduced. Adjustments in light-harvesting antenna size were observed: an increase in chlorophyll a + b/carotenoids ratio at low-light growth conditions. There was a strong positive linear correlation between the light intensity values and anthocyanin contents. Hence, T. pallida cv. purpurea acclimation to distinct environmental conditions might be related to its capacity of altering structurally and physiologically its phenotype.

Stomatal changes induced by intermittent drought in four umbu tree genotypes.

Transpiration (E), diffusive resistance (rs) and anatomical parameters were measured in plants of four grafted umbu tree genotypes (GBUs 44, 48, 50 and 68) in order to evaluate alterations induced by intermittent drought and possible genotypic variations. Transpiration measurements were taken daily until stomatal closure by withholding water. Measurements were also taken, when the plants were re-watered and the watering was interrupted again. This cycle was repeated for a period of 31 days (stress period). The control plants were also irrigated daily. A regular pattern in the stomatal opening/closing mechanism was observed throughout the watering period, exhibiting intra-specific differences. Stomatal behavior of GBU 44 and GBU 68 were influenced by air temperature (Tar), relative humidity (RH) and vapor pressure deficit (VPD), whereas GBU 50 was influenced by photosynthetically active radiation (PAR). GBU 48 was not influenced by these environmental factors. Anatomical alterations in response to drought were observed in stomatal density (SD), reductions in the stomatal index (SI) and stomatal aperture size (SA). The anatomical features of the GBU 48 genotype remained unaltered. There was an inversion in tissue proportion in GBU 44 under stress conditions, reducing the spongy parenchyma and increasing palisade parenchyma thickness. The inverse occurred with GBU 68, while the remaining genotypes were unaltered. The results found in this study suggest that GBU 68 is the most drought-sensitive genotype and anatomical changes induced by intermittent drought are not enough to explain the physiological differences between genotypes.

Water relations and organic solutes production in four umbu tree (Spondias tuberosa) genotypes under intermittent drought

In order to evaluate changes in leaf water potential (ψw) and solute accumulation induced by intermittent drought, an research was performed under greenhouse conditions using four umbu tree genotypes (GBU 44, GBU 48, GBU 50 and GBU 68) and two water treatments (control and stressed by withholding water), with four replicates. The ψw was measured in four-hour intervals during a 24-hour period at the first stomatal closure and at the end of the experimental period. Carbohydrates, amino acids, protein and proline contents were also evaluated in leaves and roots. Significant differences were found in most of the studied parameters. The lower ψw hour was between 800 h and 1200 h. GBU 50 reduced significantly ψwin stressed plants at 800 h, while control plants reduced at 1200 h . GBU 68 presented the higher ψw. The extending of the stress induced reductions to carbohydrates in the leaves of all genotypes, increases in amino acids to GBU 44 and 48, and reductions of 40% and 43% to GBU 50 and 68, respectively; results also showed alterations in proline content. In the roots, increases in carbohydrates were observed only in GBU 48. Alterations in amino acids, protein, and proline were verified. Umbu trees presented isohydric behavior maintaining high leaf water potential and a great variability in organic solutes accumulation in response to drought with marked differences among the genotypes.

Anatomia foliar como subsídio à taxonomia de Hippocrateoideae (Celastraceae) no Sudeste do Brasil

Leaf anatomy of thirteen species belonging to nine genera of the subfamily Hippocrateoideae (Celastraceae) was studied, in order to select anatomical characters to help the taxonomy at genera and species levels. The species studied were: Anthodon decussatum Ruiz & Pav., Cheiloclinium cognatum (Miers) A.C. Sm., Cheiloclinium serratum (Cambess.) A.C. Sm., Cuervea crenulata Mennega, Elachyptera micrantha (Cambess.) A.C. Sm., Hippocratea volubilis L., Peritassa flaviflora A.C. Sm., Peritassa mexiae A.C. Sm., Pristimera nervosa (Miers) A.C. Sm., Salacia crassifolia (Mart. ex Schult.) G. Don, Tontelea fluminensis (Peyr.) A.C. Sm., Tontelea leptophylla A.C. Sm. and Tontelea miersii (Peyr.) A.C. Sm. The selected anatomical characters that can be used as diagnostic for the taxonomy of the distinct genera and species are: the type of sclereids in petiole or leaf blade, stomata type, the conformation of the petiole vascular system, shape of epidermal cell walls, presence of hypodermis, occurrence of laticifers, among others.

Morphophysiological differences in leaves of Lavoisiera campos-portoana (Melastomataceae) enhance higher drought tolerance in water shortage events

Lavoisieracampos-portoana Barreto (Melastomataceae) has two kinds of leaves, pubescent and glabrous, and branches may have one or both types of leaves at the same moment. The plant is endemic to high altitude rocky fields in Brazil where rainfall is very seasonal. We predicted that these two leaf types are adaptations to different regimes of water availability. In experimental conditions of drought stress, we measured relative water content (RWC), photosynthetic pigments, chlorophyll a fluorescence and osmotic potential, and we counted stomates and measured stomatal conductance on both sides of leaves and compared these between the two leaf types. Stomatal conductance and electron transport rate at a given photosynthetic photon flux were greater in pubescent leaves than in glabrous leaves, and both declined during drought stress. Excessive photon flux density in glabrous leaves was greater during stress and after rehydration. Photosynthetic pigment content and RWC did not change between leaves, and values reduced during the stress period. Both types of leaves showed osmotic adjustment capacity, which occurred earlier in glabrous ones. These morphophysiological differences highlight the adaptation strategies of this plant to withstand drought, since the glabrous portion of the plant presents a preventive behavior, while the pubescent portion only shows the same responses in more advanced stages of drought stress.

How the long-life span leaves of Ouratea castaneifolia Engl. (Ochnaceae) differ in distinct light conditions

Plants respond to variation in luminosity leading to the existence of distinct leaf traits in plants that inhabit the understory, edge, and canopy of tropical forests. In the present work, the long-life leaves of Ouratea castaneifolia Engl. (Ochnaceae) in forest edge and understory were evaluated. Leaves of 20 individuals were collected from each habitat. Median regions of leaves from the third node were fixed in FAA. Freehand-cut transverse sections were stained in astra blue and safranin. The thickness of tissues, leaf area, specific leaf mass, and relative water content were quantified. Quantum yield of photosynthesis was measured by Fv/Fm, and instantaneous light response curves were performed to extract ETRmax, PARsat, and ∆F/Fm′sat. Quantification of photosynthetic pigments was also performed. Leaf area was lower at the forest edge, while the specific leaf mass was higher. No structural differences or differences in relative water content were observed between individuals of the two environments. The thicknesses of the cuticle on the adaxial surface, the epidermal cells on the abaxial surface, and the palisade and spongy parenchyma were greater in individuals at the forest edge. The values of Fv/Fm were around 0.8 in the predawn. In midday, higher values of Fv/Fm were observed in individuals located in the understory. Individuals of the understory had higher levels of chlorophyll a, chlorophyll b, and total chlorophyll. The morphological traits were the most plastic, but modulations in both morphology and pigment concentration may explain the maintenance of a similar predawn quantum yield between environments.

Photosynthetic and anatomical responses of three plant species at two altitudinal levels in the Neotropical savannah

The phytophysiognomies of the Neotropical savannah occur at different altitudes, which can determine distinctions in the levels of light and shade that plants are exposed. The focus of the study is analysing the functional traits of the leaves of Byrsonima verbascifolia (L.) Rich., Roupala montana Aubl. and Solanum lycocarpum A. St.-Hil. growing in phytophysiognomies at two distinct altitudes. We evaluated leaf anatomy, the quantum yield of photosystem II, and the photosynthetic pigments in plants occurring at two areas of Campo sujo, which are separated by 700 m of altitude, during the rainy season. The three plant species occurring at higher altitudes had thicker adaxial epidermis. B. verbascifolia and S. lycocarpum occurring at higher altitudes had thicker palisade parenchyma, whereas only B. verbascifolia had thicker spongy parenchyma at the same site. The quantum yield of photosystem II, and photosynthetic pigments had little differences between plants occurring at higher and lower altitudes. The results analysed show high structural modifications and low physiological alterations from altitudinal conditions. Thus, the influence of the abiotic factors appears to modulate the plastic responses of plants across altitude.