No abstract

In view of the ecological, social, and economic importance of Myracrodruon urundeuva Allemão, the objective of this study was to investigate the strategies of this species under drought during its initial phase of development. Two-monthold plants were cultivated under continuous irrigation or no irrigation for 20 d. After this period, the water-stressed plants were rehydrated for 20 d. Physiological, biochemical, and anatomical variables were evaluated on 20 th and 40 th day. Water deficit (25 and 85 % leaf relative content) caused senescence followed by leaf abscission. Growth in height was negatively affected by water deficit (37 % reduction). A decrease in the thickness of the mesophyll was accompanied by a decrease of the total chlorophyll content. Water deficit affected saccharide metabolism and altered cellular component dynamics. Enzyme activities were higher during the rehydration period than during the water stress. There was no increase in lipid peroxidation in plants subjected to water deficit. A reduction in the stomatal opening during water stress was a strategy of reducing water loss through transpiration.

The influence of two aromatic cytokinins (CKs), 6-benzylaminopurine (BAP) and meta-topolin (mT), on in vitro propagation and redox metabolism of sugarcane (Saccharum spp., variety RB98710) was investigated. Plants were cultured in Murashige and Skoog (MS) medium supplemented with mT (5 µmol.L-1) or BAP (5 or 6.66 µmol.L-1) for 40 days. The use of mT provided an increase in the multiplication rate and stem length of plants and shoots when compared to BAP. Shoots generated from the mT treatment presented low malondialdehyde (MDA) content and superoxide dismutase (SOD) activity, although they had higher hydrogen peroxide (H2O2) content. Thus, the H2O2 did not act as a stress marker, but it is related to plant growth and development processes.

No abstract

Influência da sacarose no crescimento e no perfil de pigmentos fotossintéticos em duas espécies arbóreas cultivadas in vitro Influence of sucrose on growth and profile of photosynthetics pigments in two arboreal species cultivated in vitro