Silicon fertigation and salicylic acid foliar spraying mitigate ammonium deficiency and toxicity in Eucalyptus spp. clonal seedlings

Silicon attenuates nutritional disorder of phosphorus in seedlings of Eucalyptus grandis × Eucalyptus urophylla

BACKGROUND

Nutritional disorders of phosphorus (P), due to deficiency or toxicity, reduce the development of Eucalyptus spp. seedlings. Phosphorus deficiency often results in stunted growth and reduced vigor, while phosphorus toxicity can lead to nutrient imbalances and decreased physiological function. These sensitivities highlight the need for precise management of P levels in cultivation practices. The use of the beneficial element silicon (Si) has shown promising results under nutritional stress; nevertheless, comprehensive studies on its effects on Eucalyptus spp. seedlings are still emerging. To further elucidate the role of Si under varying P conditions, an experiment was conducted with clonal seedlings of a hybrid Eucalyptus spp. (Eucalyptus grandis × Eucalyptus urophylla, A207) in a soilless cultivation system. Seedlings were propagated using the minicutting method in vermiculite-filled tubes, followed by treatment with a nutrient solution at three P concentrations: a deficient dose (0.1 mM), an adequate dose (1.0 mM) and an excessive dose (10 mM), with and without the addition of Si (2mM). This study assessed P and Si concentration, nutritional efficiency, oxidative metabolism, photosynthetic parameters, and dry matter production.

RESULTS

Si supply increased phenolic compounds production and reduced electrolyte leakage in seedlings provided with 0.1 mM of P. On the other hand, Si favored quantum efficiency of photosystem II as well as chlorophyll a content in seedlings supplemented with 10 mM of P. In general, Si attenuates P nutritional disorder by reducing the oxidative stress, favoring the non-enzymatic antioxidant system and photosynthetic parameters in seedlings of Eucalyptus grandis × Eucalyptus urophylla.

CONCLUSION

The results of this study indicate that Eucalyptus grandis × Eucalyptus urophylla seedlings are sensitive to P deficiency and toxicity and Si has shown a beneficial effect, attenuating P nutritional disorder by reducing the oxidative stress, favoring the non-enzymatic antioxidant system and photosynthetic parameters.

Supraparticles as slow-release fertiliser in seedling potential growth of Eucalyptus urograndis and greenhouse gas flux impacts

Slow-release urea fertilisers have been shown to present acceptable values for plant yield and mitigate the harmful effect of soil emission gases. This study synthesises a slow-release fertiliser containing fumed-nanosilica, nanofibrillated cellulose as well as sodium alginate as a urea carrier to analyse the growth parameters of Eucalyptus urograndis seedlings and potential emission of soil gases, N₂O, CH₄, CO₂ and ammonia volatilisation. The developed supraparticles, arranged layered nanoparticle structure, presented a decrease in the normal nitrogen content of urea of 19%, which is attributed to the binding of this element. A good electrostatic interaction between the elements was confirmed by the FTIR with 20% of nitrogen content from its chemical composition and an increase in thermal degradation of the main components when synthesised. The profile of urea release presented to be as first-order with 85% of this compound was released only after 60 days. These characteristics led to statistically increased growth of Eucalyptus seedlings compared to the controls, which improves with higher dosages of urea. Values of biomass and characteristics of the plant were used for principal component analysis which resulted in good cluster formation based on the upward concentration of urea added to the plant. Nevertheless, flux gases were statistically higher for certain time periods on lower urea particle concentration, while increased concentration presented N₂O emissions within standard rates with no significant variation in the other measured gases, which was attributed to the soil microbial targeted consumption. Therefore, this material can be beneficial in the agriculture industry.

Does energy cost constitute the primary cause of ammonium toxicity in plants?

Nitrate (NO₃^-) and ammonium (NH₄⁺) are the main nitrogen (N) sources and key determinants for plant growth and development. In recent decades, NH₄⁺, which is a double-sided N compound, has attracted considerable amounts of attention from researchers. Elucidating the mechanisms of NH₄⁺ toxicity and exploring the means to overcome this toxicity are necessary to improve agricultural sustainability. In this review, we discuss the current knowledge concerning the energy consumption and production underlying NH₄⁺ metabolism and toxicity in plants, such as N uptake; assimilation; cellular pH homeostasis; and functions of the plasma membrane (PM), vacuolar H⁺-ATPase and H⁺-pyrophosphatase (H⁺-PPase). We also discuss whether the overconsumption of energy is the primary cause of NH₄⁺ toxicity or constitutes a fundamental strategy for plants to adapt to high-NH₄⁺ stress. In addition, the effects of regulators on energy production and consumption and other physiological processes are listed for evaluating the possibility of high energy costs associated with NH₄⁺ toxicity. This review is helpful for exploring the tolerance mechanisms and for developing NH₄⁺-tolerant varieties as well as agronomic techniques to alleviate the effects of NH₄⁺ stress in the field.