# Fungi of the _Trichoderma_ Genus: Future Perspectives of Benefits in Sustainable Agriculture
## 5 Application of _Trichoderma_ Fungi in Promoting Plant Growth
### Induction of Plant Resistance to Abiotic Stress  
[PERSON] et al. [163] define plant tolerance to abiotic stress as the ability to maintain crop yields at an appropriate level despite extreme environmental conditions. According to [PERSON] et al. [32] and [PERSON] et al. [34], the factors that most affect the quantity and quality of crops are temperature variability, inadequate level of soil salinity, drought and lack of rainfall, and the presence of toxic heavy metals in the soil. According to [PERSON] et al. [164], stressful environmental conditions: reduce the efficiency of photosynthesis, inhibit chlorophyll biosynthesis and seed germination; interfere with the proper functioning of hormonal and water management, the conductivity of the stomata, uptake, and transport of nutrients in the plant; and induce the formation of reactive oxygen forms (ROS), which destroy plant biomolecules (lipid, protein, nucleic acids) [20]. These changes lead to damage to individual cells and tissues, inhibition of the growth of roots and shoots, premature aging, chlorosis, necrosis, and ultimately the death of the entire organism [165; 166]. In addition, stress interferes with the uptake and accumulation of carbon, which is necessary for the synthesis of cellular structures and defense molecules [163; 167]. It has been shown that _Trichoderma_ sp. fungi can reduce the effects of abiotic stress in plants, mainly by regulating the activity of their enzymatic and non-enzymatic antioxidants, production, and regulation of phytohormones and osmolites (Table 4). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Types of Stress** &
\begin{tabular}{c} **Species of** \\ _Trichoderma_ \\ \end{tabular} & **Crops** & \multicolumn{2}{c}{**Mechanisms of Action**} & **Reference** \\ \hline High temperature & _Trichoderma koningii_ & tomato & \(\bullet\) & Increasing the activity of antioxidant enzymes of plants; \(\bullet\) & \\ High temperature & _Trichoderma koningii_ & tomato & \(\bullet\) & Regulating the level of proline, starch, proteins, phenols in the plant; \(\bullet\) & [168] \\  & & & \(\bullet\) & Reducing the level of hydrogen peroxide in the plant. & \\ Low temperature & _Trichoderma harzianum_ & tomato & \(\bullet\) & Reducing lipid peroxidation; \(\bullet\) & \\ Low temperature & _Trichoderma harzianum_ & tomato & \(\bullet\) & Regulating the level of osmolites and proline in the plant; & [169] \\  & & & \(\bullet\) & Increasing the water content of the leaves. & \\ \hline Salinity & _Trichoderma_ & wheat & \(\bullet\) & Increasing the activity of antioxidant enzymes of plants; \(\bullet\) & \\  & _Trichoderma_ & _Trichoderma_ & \(\bullet\) & Reducing the level of hydrogen peroxide in the plant; & [170] \\  & & & \(\bullet\) & Increasing the level of salicylic acid in the plant. & \\ Salinity & _Trichoderma asperellum_ & cucumber & \(\bullet\) & Increasing the level of gibberell, auxins and abscisic acid in the plant; & \\  & & & & \\  & & & & \\  & & & & \\ Salinity & _Trichoderma asperellum_ & cucumber & \(\bullet\) & Solubilization of unavailable & \\  & & & & phosphorus, increasing the activity of phosphatase and phytase. & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mechanisms of _Trichoderma_ fungi in inducing plant resistance to abiotic stress. The main mechanism used by _Trichoderma_ fungi to increase plant tolerance to stressful environmental conditions is the induction of the activity of plant antioxidant enzymes such as ascorbate peroxidase (APX), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), glutathione s-transferase (GST), phenylalanine ammonia- lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), superoxide dismutase (SOD), monodehydroascorbate reductase (MDHAR), and dehydrodiscorbate reductase (DHAR). In addition, _Trichoderma_ sp. fungi activate non-enzymatic plant antioxidants such as proline, ascorbic acid, betaine, and glutathione.