The beneficial effects of silicon (Si) on plants have been widely reported for its fruit qualitative improvements, growth gains, and protection against abiotic and biotic stresses. This study aimed to evaluate the combined effect of soil water potential (Ψs) (−30 and −60 kPa) and the foliar application of Si (0.0 (control), 1.0, 2.0, 3.0, and 4.0 g L−1) in the development of tomatoes grown in a greenhouse. We evaluated the biometric parameters and gas exchange in three periods (20, 34, and 48 days after planting). The rates of transpiration (E), stomatal conductance (gs), and net photosynthesis assimilation (An) were lower when the plants were subjected to water deficit. The foliar application of Si attenuated the effect of the water deficit in both levels applied to the crop. A high response was observed at −60 kPa, regardless of the evaluated period. However, a significant effect was not observed on the relative chlorophyll index and biomass accumulation when Si was applied. A foliar application up to 2.8 g L−1 promotes increases in An,gs, and E. It is highlighted that Si can promote improvements in gas exchange when plants are affected by a water deficit.

Computational fluid dynamic (CFD) can be used to quantify the internal flow variables of xylem conducting vessels. This study aims to analyze through numerical simulations the xylem water ascent of African mahogany (Khaya grandifoliola) cultivated under different irrigation regimes. We determined a geometric model, defined through the variability of the anatomical structures of the species, observing characteristics of the xylem vessels such as diameter, length, number of pits, and average surface area of the pits. Then we applied numerical simulation through an Eulerian mathematical model with the discretization of volumes via CFD. Compared to other models, we observed that numerical simulation using CFD represented the xylem microstructures in a greater level of detail, contributing to the understanding of the flow of xylem vessels and the interference of its various structures. Analyzing the micrographs, we observed the non-irrigated vessels had a higher number of pits in the secondary wall thickening when compared to the irrigated treatments. This trend influenced the variability of the radial flow of the xylem vessels, causing greater fluid movement in this region and decreasing the influence of the smooth part of the wall, resulting in a lower total resistance of these vessels.

Full plant growth and development require, among others, air temperatures and water availability at levels appropriate to each crop. The effect of temperature on plant development can be represented by the thermal sum, which requires the lower basal temperature for each plant species. However, plant responses may be different when associated with different soil water contents. This work determined the lower and upper basal temperature of Jatropha curcas L. and verified the relationship between thermal sum and crop development under different water regimes, in the climatic conditions of Goiânia, GO, Brazil. We evaluated twenty-four plants cultivated at the planting density of 2,222.2 plants ha-1. Of these, twelve plants were irrigated from October 2010 to October 2012, whereas the other twelve remained unirrigated. Basal temperatures were estimated by four different methods described in the literature, in two phases of observation, maturity and total cycle. From the results, regression analysis was performed. The lower basal temperature was 4.9 and 7.2 °C, and upper basal temperature was 38.8 and 36.8 °C, respectively, for the maturity and total cycle stages. The accumulated thermal sum for the complete plant development of jatropha was 10,314.55 DD (±1574.73) for the non-irrigated treatment, and 9,260.67 DD (±735.06) for the irrigated treatment. The results of plant development showed good coefficient of determination in relation to the accumulated thermal sum.

The tomato crop is almost totally irrigated. Among the irrigation methods utilized, mechanized sprinkling by center pivot stands out in tomato cultivation. A cultural treatment used in the tomato is the synchronization of the irrigations with the applications of the pesticides since with the leaf wetting the plants become unprotected and susceptible to diseases. In an attempt to reduce pesticide applications, growers seek to increase the time between irrigations, however, there are limitations, inherent to the soil and the irrigation system itself. The objective of this work was to simulate the soil water runoff tendency for irrigation management in the tomato crop, simulating three different types of soils (sandy, medium and clayey), three declines (0, 5 and 10%), and two types of deflectors (I-Wob and Spray). For this, four pivot sizes (25, 50, 75 and 100 ha) were defined and the methodology of maximum allowable precipitation estimated by the Newton-Raphson numerical technique was used to verify the different runoff conditions. The results showed that clayey soils are more susceptible when compared to medium and sandy soils, to surface runoff. Pivots of 100, 75 and 50 ha present greater susceptibility to runoff, with 25 ha being the best suitability for infiltration capacity in both soils. There is a percentage reduction of the maximum allowable rainfall of 40.74 % (±1.54) when the terrain is plan and pass to have 5% inclination and 22.99% (±1.47) between 5 and 10 %. I-Wob type deflectors have a better distribution of application, a consequently better relation with the maximum allowable precipitation intensity and less possibility of the surface runoff.

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