Biostimulants are products that reduce the need for fertilizers and increase plant growth, resistance to water and abiotic stresses. In small concentrations, these substances are efficient, favoring the good performance of the plant’s vital processes, and allowing high yields and good quality products. In addition, biostimulants applied to plants enhance nutrition efficiency, abiotic stress tolerance and/or plant quality traits, regardless of its nutrient contents. Several researches have been developed in order to evaluate the biostimulants in improving plant development subjected to stresses, saline environment, and development of seedlings, among others. Furthermore, various raw materials have been used in biostimulant compositions, such as humic acids, hormones, algae extracts, and plant growth-promoting bacteria. In this sense, this chapter aims to approach the use of biostimulants in plant growth according to the raw material used in their compositions as well as their effects on plants subjected to abiotic stresses.
Part of the book: Biostimulants in Plant Science
Water stress is one of the most important environmental factors inducing physiological changes in plants, such as decreasing water potential of the cells and the stomatal closure, resulting in reduced CO2 availability for the plants and inhibiting photosynthesis. One common feature of these stress conditions is the development of oxidative processes mediated by reactive oxygen species (ROS). ROS accumulate in the cells and cause damage in important cellular components, such as thylakoids and chloroplasts. Plants have antioxidant defense systems to cope with ROS. Antioxidants enzymes superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) are efficient scavengers of ROS: superoxide, hydroxyl radicals, and singlet oxygen. The activities of antioxidant enzymes in plants are normally favored when plants are subjected to some kind of improvement in the conditions in which they are grown. In this sense, biostimulants cause changes in vital and structural processes in order to influence plant growth through improved tolerance to abiotic stresses by increasing the antioxidant activity in plants.
Part of the book: Plant Stress Physiology
Biochar is the term given to biomass subjected to the process of change in the composition by the action of high temperatures. Advantages of biochar in soil quality have been reported, including amelioration of salinity effects. Salinity has a negative effect on soil physical properties and plant production by adversely affecting the process of plant growth, hence seed germination, nutrient uptake, and yield. Moreover, salt stress causes oxidative stress in plant and the reduction in antioxidant enzyme activities. Biochar is an amendment, which could decrease the negative effect of salt stress on crop growth and production. Application of biochar enriches mineral nutrients; improves the soil’s physical, chemical, and biological characteristics such as bulk density, hydrological properties, aggregate structure, ion exchange capacity, and microbial activity; and consequently enhances plant growth. Enhancing physical properties, biochar balances water holding capacity and air porosity in soils. Biochar promotes benefits in plant growth in saline soils through reduction in oxidation stress and in osmotic stress, lower production of phytohormones, improvement in stomatal density and conductance, improvement in seed germination, and the promotion of microbial activities. Biochar amendment can contribute to reduce salt stress in plants under saline condition due to its high salt adsorption capability.
Part of the book: Applications of Biochar for Environmental Safety