Abstract: Tomato is a crop sensitive to water deficit and the responses of seeds to germination under these conditions involve biochemical, physiological, and molecular processes. The aim of this study was to evaluate the physical, physiological, and biochemical changes in tomato seeds osmoprimed with selenium (Se) and subjected to water deficit during germination. Tomato seeds of the LA 4050 and LA 3475 accessions were osmoprimed with PEG 6000 solution (-1.0 MPa) plus Na2SeO4 (12.5 μM) or only with PEG 6000 solution for 24 h or unprimed. The seeds from the different treatments were subjected to water deficit (-0.3 MPa) or to control (0 MPa). Image analyses were performed (X-ray), physiological variables were obtained by the germination test and activities of SOD, CAT and POX enzymes were determined. Osmopriming, especially with PEG, provided the seeds of both accessions with higher densities and gray mean when compared to unprimed ones. Seeds under water deficit showed lower physiological performance and lower enzymatic activity. Se did not induce seed resistance to water deficit. Osmopriming with PEG 6000 at -1.0 MPa is an efficient technique for improving the physiological quality of seeds of tomato accessions susceptible and tolerant to water deficit. Moreover, the antioxidant enzyme CAT proved to be an indicator of oxidative stress tolerance in tomato seedlings under water deficit.

Resumo: O tomate é uma cultura sensível ao déficit hídrico e as respostas de sementes à germinação sob essas condições envolvem processos bioquímicos, fisiológicos e moleculares. O objetivo do trabalho foi avaliar as alterações físicas, fisiológicas e bioquímicas em sementes de tomate osmocondicionadas com selênio (Se) e, posteriormente, submetidas ao déficit hídrico durante a germinação. Sementes de tomate das linhagens LA 4050 e LA 3475 foram osmocondicionadas com solução PEG 6000 (-1,0 MPa) mais Na2SeO4 (12,5 μM) ou apenas com solução de PEG 6000 por 24 h ou não condicionadas. As sementes provenientes dos diferentes tratamentos foram submetidas ao déficit hídrico (-0,3 MPa) ou ao controle (0 MPa). Foram realizadas análises de imagens (raios X); obtenção de variáveis fisiológicas pelo teste de germinação e atividades das enzimas SOD, CAT e POX. O osmocondicionamento, sobretudo com PEG, proporcionou às sementes de ambas as linhagens maiores densidades e média de cinza quando comparadas às não condicionadas. As sementes sob déficit hídrico apresentaram menor desempenho fisiológico e atividade enzimática. O Se não induziu resistência às sementes ao déficit hídrico. O osmocondicionamento com PEG 6000 a -1,0 MPa é eficiente para melhoria da qualidade fisiológica de sementes dos acessos de tomate suscetíveis e tolerantes ao déficit hídrico. Além disso, a enzima antioxidante CAT se mostrou indicadora da tolerância ao estresse oxidativo em plântulas de tomate sob déficit hídrico.

A magnetic catalyst (sample MCat) consisting of KI supported on a mixture of silica and maghemite (γ-Fe2O3) was prepared and used in the transesterification reaction for the synthesis of biodiesel. The energy dispersive X-ray spectrum of the catalyst showed signals due to Si, Fe, K, and I. Powder X-ray diffraction data revealed the amorphous nature of the SiO2 and the duly impregnation of the support with KI. 57Fe Mössbauer spectroscopy and magnetization measurements confirmed the ferrimagnetic iron oxide in the catalyst to be maghemite. N2 adsorption-desorption data indicated that the silica is mesoporous with a specific area of 352 m2 g-1, enabling the impregnation of 40 and 11 wt.% of KI and maghemite, respectively, according to the chemical composition obtained by the X-ray fluorescence measurements. The MCat was found to be efficient in the transesterification reaction in the macaúba and soybean oils. The MCat was easily removed from the reaction medium, with a hand magnet, and efficiently reused for more four consecutive reaction cycles. The good catalytic activity along with its magnetic behavior, high chemical stability and recyclability make the MCat a suitable material for the green synthesis of biodiesel.