How Do Biostimulants Affect Plant Growth Under Drought Conditions?

Plants are constantly subjected to environmental stresses, with drought being one of the most common and damaging factors. Drought stress can negatively impact plant growth, productivity, and overall health. To mitigate these adverse effects, various agricultural practices and inputs have been developed, including biostimulants. Biostimulants are natural or biologically derived substances that enhance plant growth and resilience, especially under challenging conditions such as drought. In this article, we will explore how biostimulants affect plant growth under drought conditions and their potential role in sustainable agriculture.

1. What Are Biostimulants?

Biostimulants are substances or microorganisms that, when applied to plants or soils, enhance plant growth, vigor, and resilience, without directly providing essential nutrients like traditional fertilizers. They work by stimulating plant physiological processes, increasing nutrient uptake, improving stress tolerance, or promoting soil health. Biostimulants are typically composed of natural ingredients, such as seaweed extracts, humic substances, amino acids, beneficial microbes, and plant hormones.

• Plant Hormones: Biostimulants may include plant growth regulators such as auxins, cytokinins, and gibberellins, which influence plant cell division and stress tolerance.

• Microbial Inoculants: Some biostimulants contain beneficial microorganisms like mycorrhizal fungi or rhizobacteria, which improve nutrient uptake and soil structure.

• Natural Extracts: Seaweed, humic acids, and other natural plant extracts are commonly used for their ability to stimulate plant defenses and promote growth under stress.

  
  

By influencing the plant’s internal processes, biostimulants help improve overall health and adaptability, making them especially useful during times of environmental stress like drought.

2. How Do Biostimulants Improve Drought Tolerance?

Drought stress occurs when water availability is insufficient to meet the plant’s needs, leading to reduced growth, wilting, and even death. Biostimulants enhance plant drought tolerance through several mechanisms, including improving water use efficiency, boosting antioxidant activity, and regulating stomatal conductance. Here’s how:

• Improved Water Use Efficiency: Biostimulants can help plants make better use of available water by improving root development and increasing the ability of roots to absorb water. Some biostimulants stimulate the growth of deeper, more extensive root systems, which can reach water stored deeper in the soil.

• Enhanced Osmotic Regulation: Certain biostimulants promote the synthesis of osmoprotectants like proline and sugars, which help plants retain water and maintain cell function under drought stress. These osmoprotectants balance osmotic pressure, enabling cells to maintain hydration during water shortages.

• Improved Stomatal Regulation: Biostimulants can regulate the opening and closing of stomata (the tiny pores on plant leaves), helping plants conserve water by reducing transpiration. This allows plants to retain moisture while still carrying out necessary functions like gas exchange.

• Enhanced Antioxidant Activity: Drought stress increases the production of reactive oxygen species (ROS), which can damage plant cells. Biostimulants help enhance antioxidant defenses, such as catalase and superoxide dismutase, which neutralize ROS and reduce oxidative damage during periods of water scarcity.

  
  

By improving water use efficiency, osmotic regulation, and antioxidant defense mechanisms, biostimulants help plants better withstand and recover from the adverse effects of drought.

Biostimulants

3. Biostimulants Promote Root Development

Root development is a critical factor in drought tolerance. Plants with stronger and more extensive root systems are better equipped to access deeper water reserves in the soil. Biostimulants, particularly those containing natural growth regulators, can stimulate root growth and improve root architecture, which is essential under drought conditions. Here’s how biostimulants impact root development:

• Root Length and Density: Biostimulants, such as seaweed extracts and humic substances, have been shown to increase root length and root density. This results in a greater root surface area, allowing plants to absorb more water and nutrients.

• Root Health: Some biostimulants promote the health of root cells, enhancing their resistance to pathogens and helping them grow in adverse conditions.

• Mycorrhizal Symbiosis: Biostimulants that contain beneficial fungi, like mycorrhizae, establish symbiotic relationships with plant roots. These fungi extend the root system’s reach, improving water and nutrient absorption while also enhancing plant stress tolerance

  
  

By promoting healthier, more extensive root systems, biostimulants enable plants to access moisture more efficiently, even in drought-prone soils.

4. Biostimulants Reduce Transpiration and Water Loss

Transpiration is the process through which water is lost from plant leaves to the atmosphere. Under drought conditions, excessive transpiration can lead to water deficits, which can harm the plant. Biostimulants can reduce transpiration by regulating stomatal activity, which in turn minimizes water loss. Here’s how biostimulants help reduce transpiration:

• Stomatal Closure: Some biostimulants contain plant hormones that help control the opening and closing of stomata, reducing the amount of water lost during transpiration.

• Cuticular Protection: Biostimulants can also strengthen the plant’s cuticle, the waxy layer on the surface of leaves, which helps reduce water loss by limiting evaporation.

• Improved Water Retention: Biostimulants like humic acids help improve the plant’s ability to retain water in cells, reducing overall water loss during periods of water stress.

  
  

By reducing water loss through improved stomatal regulation and cuticular protection, biostimulants help conserve water, enabling plants to survive longer under drought conditions.

5. Enhanced Plant Growth and Yield During Drought

Even under drought stress, plants still require nutrients to grow and produce a good yield. Biostimulants enhance nutrient uptake, improve photosynthesis, and promote overall plant growth, even in challenging conditions. This ensures that plants can continue growing and producing fruit or seeds, despite limited water availability.

• Increased Photosynthetic Efficiency: Biostimulants can enhance the photosynthetic activity of plants, enabling them to produce more energy even under water stress. This helps the plant maintain growth and development during drought conditions.

• Better Nutrient Uptake: By improving root growth and soil conditions, biostimulants enhance nutrient uptake, which is essential for maintaining growth and improving resistance to drought stress.

• Improved Yield: Studies have shown that biostimulants can help maintain or even improve crop yield under drought stress. This is particularly important for agricultural production, where droughts can significantly reduce yields.

  
  

In addition to mitigating the immediate effects of drought, biostimulants help ensure that plants continue to grow and produce high-quality yields, even in times of limited water availability.

6. Conclusion

Biostimulants provide an effective tool for improving plant resilience under drought conditions. By enhancing water use efficiency, promoting root development, reducing transpiration, and supporting overall plant growth, biostimulants help plants better survive and thrive under water-limited conditions. Whether through improved nutrient uptake, enhanced antioxidant activity, or better stomatal regulation, biostimulants offer a sustainable solution to mitigate the adverse effects of drought and improve crop yield and quality. As climate change and water scarcity continue to pose challenges to global agriculture, biostimulants will play an increasingly important role in ensuring food security and sustainable farming practices.