Rodrigo de Queiroga Miranda

Germination of Prosopis juliflora (Sw.) D.C. seeds at different osmotic potentials and temperatures

The effects of osmolytes, osmotic potential (Ψs), temperature, and their interactions on the germinability, germination rate, and other germination parameters of the invasive shrub Prosopis juliflora, which grows in the semiarid environmental conditions of the Caatinga in northeast Brazil, were evaluated. To study the effects of polyethylene glycol (PEG) and NaCl stress and temperature on germination, two separate experiments were carried out at the Plant Ecophysiology Laboratory of the Federal University of Pernambuco in 2011. The overall germinability decreased significantly with increases in both PEG (one-way anova, F4,75 = 111.21, P ≤ 0.001) and NaCl (one-way anova, F4,75 = 12.82, P ≤ 0.001); however, the effects were more accentuated with PEG than NaCl. The PEG-treated seeds maintained their germinability, even when they were subjected to a Ψs = −1 MPa after being rinsed and allowed to germinate on deionized water. In contrast, NaCl-treated seeds usually lost their ability to germinate; this fact was possibly linked to the accumulation of Na+ and Cl− in the cells, which may have contributed to a loss of membrane function that led to the death of the embryos. Although numerous studies describing seed germination in the presence of osmolytes have been conducted, studies that show the interactions between osmolytes, osmotic potentials, and temperature are scarce. The present study is the first to describe these interactions for P. juliflora seeds.

Reliability of MODIS Evapotranspiration Products for Heterogeneous Dry Forest: A Study Case of Caatinga

Evapotranspiration (ET) is normally considered as the sum of all water that evaporates from the soil and transpires from plants. However, accurately estimating ET from complex landscapes can be difficult because of its high spatial heterogeneity and diversity of driver factors, which make extrapolation of data from a point to a larger area quite inaccurate. In this paper, we hypothesize that MODIS products can be of use to estimate ET in areas of Caatinga vegetation, the hydrology of which has not been adequately studied. The experiment was conducted in a preserved level area of Caatinga in which meteorological and water flux measures were taken throughout 2012 by eddy covariance. Evapotranspiration estimates from eddy covariance were compared with remotely sensed evapotranspiration estimates from MOD16A2 and SAFER products. Correlations were performed at monthly, 8-day, and daily scales; and produced values of monthly scale = 0.92, 8-day scale = 0.88, and daily scale = 0.85 for the SAFER algorithm. Monthly MOD16A2 data produced a value of , and they may be useful because they are free, downloadable, and easy to use by researchers and governments.