Action of silicon on the activity of antioxidant enzymes and on physiological mechanisms mitigates water deficit in sugarcane and energy cane plants.

Production of sugarcane and more recently of energy cane strengthen renewable bioenergy production capacity. However, droughts resulting from climate change have limited the production of these crops. One of the strategies to attenuate water deficit damage in these crops is the use of silicate, which contributes to plant physiology. This strategy is likely to increase water use efficiency, thus promoting crop sustainability. Notwithstanding, studies on this issue are still incipient. This study assesses whether Si applied via fertigation and foliar spraying in the seedling production phase and as a complement after seedling transplanting to the soil is efficient in attenuating water deficit in sugarcane and energy cane. The study further elucidates physiological and biochemical mechanisms involved in this process. For this, the authors conducted two experiments: one with sugarcane and the other with energy cane. Treatments were arranged in randomized blocks with 5 replications, in a 2 × 2 factorial scheme. Factors consisted of the absence (-Si) and presence of Si (+ Si) applied via fertigation and foliar spraying; and two water regimes: 70% (without water deficit) and 30% (severe water deficit) of the soil water retention capacity. Silicon was supplied during the formation phase of presprouted seedlings and during the transplanting of seedlings to pots filled with samples of Entisol (Quartzipsamment). In these pots, water regimes were induced from 7 to 160 days after transplanting. Severe water deficit reduced the water content and water potential of plants. This situation induced oxidative stress and impaired gas exchange and photosynthetic water use efficiency, reducing plant growth. Silicon supply via fertigation in association with foliar spraying in the seedling formation phase with complementation after transplanting was efficient in increasing Si accumulation in the plants. Silicon was effective in attenuating severe water deficit damage up to initial culm formation through mechanisms that maintain water and physiological balance by favoring the antioxidant defense system in sugarcane and energy cane plants.

Postharvest quality of yellow passion fruit produced in soil with bovine biofertilizer and nitrogen.

The use of soil conditioners as bovine biofertilizer associated with mineral fertilization affect the physical and physicochemical quality of passion fruit. For fruit growth, post-harvest quality is crucial for production chain development, as it is the characteristic most used by the fresh consumption market for this fruit. In this sense, an experiment was carried out to investigate the effects of doses of bovine biofertilizer in the soil with and without nitrogen fertilization in the cultivation of yellow passion fruit. A randomized block design was adopted, with three replications in a 5×2 factorial scheme, referring to five doses of liquid bovine biofertilizer (B) diluted in water (A): 0% - control (0B + 4A); 25% (1B + 3A); 50% (2B + 2A); 75% (3B + 1A); and 100% (4B + 0A) with and without nitrogen fertilization applied to the soil. Urea was the nitrogen source used in this study. A total of 10 g plant-1 of N was applied monthly at 30 and 60 days after transplanting, and after that age, 20 g plant-1 was applied until the end of harvest. During the final phase of production and ripening, twelve fruits were harvested from each treatment in physiological maturation for physical and physicochemical characterization. The following analyses were performed: longitudinal diameter, transversal diameter, number of seeds per fruit, peel firmness, pulp yield, fruit peel percentage, pulp pH, soluble solids content; titratable acidity and soluble solids content/titratable acidity ratio. Data underwent analysis of variance by the F test means for nitrogen were compared by Tukey's test and means for bovine biofertilizer, by regression. Nitrogen enhances the positive effect of bovine biofertilizer on the postharvest quality of yellow passion fruit. The association of biofertilizer and nitrogen improves fruit quality in comparison to plants without these inputs, except for pulp yield and fruit peel percentage, which suffered isolated effects from the factors. High doses of biofertilizer, above 75 and 100%, reduce soluble solids content and increase titratable acidity. The bovine biofertilizer has promising effects, but it does not replace nitrogen fertilization on the postharvest quality of yellow passion fruit.

Water deficit modifies C:N:P stoichiometry affecting sugarcane and energy cane yield and its relationships with silicon supply.

Climate change has increased the occurrence of water deficit in regions where sugarcane and energy cane are cultivated, jeopardizing dry matter production of stems. It was hypothesized that the reasons behind this fact relate to C:N:P stoichiometric modifications in these species that impair the conversion rates of accumulated nutrients in the stems, which could be attenuated by supplying silicon (Si) to the crops. Thus, the aims of this study were to evaluate the effects of water deficit in sugarcane and energy cane ratoons in the presence and absence of Si, in the C:N:P stoichiometry of stems, in the use efficiency of these nutrients and in the accumulation of dry matter in stems. Two experiments were carried out, using sugarcane (Saccharum officinarum) and energy cane (S. spontaneum), cultivated in pots filled with a Typic Quartzipisamment. The treatments for both experiments were arranged in a factorial scheme 2 × 2, without (70% of the soil's water retention capacity) and with (30% of the capacity) water deficit, without and with the application of Si via fertirrigation, associated with foliar pulverization, both at a concentration of 2.5 mmol L-1, arranged in randomized blocks. The reduction in dry matter production of stems in both species caused by water deficit was due to modifications of the C, N and P stoichiometric homeostasis, but the benefit of Si in these plants when increasing dry matter production was not a reflection of the change in homeostasis, thus it may be involved in other mechanisms that remain unknown and should be further studied.