How Biologicals Help Crops Handle Heat, Drought, and Stress

Dr. Ankita Garkoti
Jul 3
9 min read

Introduction

Agriculture today faces the challenge of meeting rising demand for food production while adapting to unpredictable and increasingly extreme environmental conditions. Climate variability is increasing the frequency and severity of heat waves, prolonged droughts, and erratic rainfall events, making environmental stress one of the greatest challenges facing modern agriculture. Climate change has intensified abiotic stresses such as heat waves, drought, and irregular weather patterns, which negatively affect crop growth and reduce productivity. Drought and heat stress are among the most significant abiotic factors limiting crop productivity and threatening global food security. Multiple studies have shown that heat and drought stress can cause substantial reductions in crop yields, with losses reaching up to 50% under extreme environmental conditions. (1) Traditional approaches such as irrigation, chemical fertilizers, and breeding have improved crop productivity but may be limited by high costs, environmental impacts, and slow adaptation to changing climate conditions.

Biological solutions such as biofertilizers, plant growth-promoting microorganisms, and biostimulants are emerging as powerful tools for sustainable agriculture. These naturally derived inputs enhance nutrient availability and strengthen plant resilience by modulating key physiological, biochemical, and molecular processes involved in stress adaptation. As a result, they improve plant tolerance to abiotic stresses such as drought and heat, promoting healthier growth and higher productivity under changing climatic conditions.

Understanding Stress in Crops

Plants are continuously exposed to a range of environmental stresses, including drought, high temperature, salinity, and nutrient limitations. Among these, drought and heat are particularly damaging and often occur simultaneously, leading to compounded negative effects on plant growth and productivity.

Drought stress occurs when soil water availability is insufficient and atmospheric conditions promote excessive water loss. It develops when the balance between plant water uptake from the soil and water loss through evapotranspiration is disrupted, often under low-humidity, high-temperature conditions. (1) Under drought conditions, plants experience reduced water availability, leading to stomatal closure, decreased photosynthesis, and impaired growth.

Heat stress occurs when air temperatures rise above the optimum range for normal plant growth for a sufficient period to disrupt physiological processes. If severe or prolonged, heat stress can damage proteins, cellular membranes, photosynthetic machinery, and reproductive tissues, resulting in reduced growth, lower yields, and diminished crop quality. Reproductive stages such as flowering and pollination are often the most sensitive to heat stress, making even short periods of high temperatures capable of significantly reducing crop yield. Heat stress also increases the production of reactive oxygen species (ROS), which can cause oxidative damage to cells if not effectively neutralized by the plant's antioxidant defence systems.(1)

Together, drought and heat stress reduce crop growth, yield, and quality by disrupting water relations, photosynthesis, nutrient uptake, and other essential physiological processes. To counteract these conditions, plants activate a complex network of defence mechanisms, including hormonal signalling pathways, antioxidant enzyme systems, osmotic adjustment, and stress-responsive gene expression. However, under severe or prolonged stress, these natural defence systems are often insufficient to fully protect the plant. This limitation highlights the value of biological solutions, which can strengthen and reinforce the plant's inherent stress-tolerance mechanisms.

Figure 1: Plant Abiotic Stress Response

Source: Adapted from Lamaoui,M.(2018). Heat and Drought stresses in crops and approaches for their mitigation. Frontiers in Plant Science,9 : 1476.

Biologicals and Their Role in Drought and Heat Stress

Biological solutions have emerged as an environmentally safe and effective approach to mitigate the adverse effects of drought and heat stress in plants. Unlike conventional fertilizers that primarily supply nutrients, biologicals interact with plants and the soil microbiome to stimulate natural biological and physiological processes. These agents interact with plants and soil ecosystems to improve nutrient availability, enhance root development, and strengthen stress tolerance.

Biofertilizers, including endophytic fungi (EF), arbuscular mycorrhizal fungi (AMF), plant growth-promoting bacteria (PGPB), and other naturally derived compounds, play a key role in improving plant resilience under water-limited and high-temperature conditions. Among these biological solutions, beneficial microbes such as plant growth-promoting rhizobacteria (PGPR) and AMF are particularly important in supporting plant adaptation to stress.

Research shows that these beneficial microorganisms improve soil structure, enhance nutrient uptake, and regulate plant water relations, thereby enabling plants to better cope with drought and heat stress. (2) In addition, these biological agents help regulate stress-responsive pathways in plants, enabling better physiological adjustment under adverse conditions. By strengthening antioxidant defence systems, improving osmotic balance, and supporting hormonal regulation, they reduce the damaging effects of drought and heat stress.

As a result, biologicals not only alleviate stress-induced damage but also support sustained plant growth and productivity under challenging environmental conditions, making them a promising tool for climate-resilient agriculture.

Figure 2: Biologicals and Their Role in Drought and Heat Stress

Source: Adapted from Aroca, R., Ruiz- Lozano, J.M. 2012. Arbuscular mycorrhizal fungi- a natural tool to impart abiotic stress tolerance in plants. Journal of Plant Physiology, 169(10), 969-978.

How Biologicals Improve Stress Tolerance:

Biologicals improve plant stress tolerance by strengthening the natural processes that help plants cope with environmental challenges. Beneficial microorganisms enhance root growth and water uptake, improve nutrient availability, and support better soil- plant interactions. They also regulate plant hormones, promote osmotic balance, and activate antioxidant defence systems that protect cells from stress-induced damage. By improving soil health and microbial activity, biologicals create a more resilient root environment, enabling plants to maintain growth and productivity under drought, heat, and other abiotic stresses.

1. Enhanced Root Growth and Water Uptake:

One of the key mechanisms through which biologicals improve plant stress tolerance is by promoting enhanced root development and efficient water acquisition. Beneficial microbial inoculants stimulate root growth by improving root branching, elongation, and overall root architecture, including increased lateral root formation, root hair density, and total root surface area. These improvements enable plants to explore a larger volume of soil and access water and nutrients more efficiently, including from deeper soil layers during periods of drought.

Mycorrhizal fungi establish symbiotic associations with plant roots and extend the root absorption zone through their extensive network of fungal hyphae. This expanded hyphal network enhances water absorption, improves nutrient acquisition, and increases water-use efficiency, particularly under drought stress conditions. In addition, inoculation with arbuscular mycorrhizal fungi (AMF) supports better root system development and improves photosynthetic capacity by maintaining plant hydration and nutrient availability (2).

Improved root architecture and microbial activity also increase water-use efficiency (WUE), allowing plants to produce more biomass or yield with the same or less available water. Enhanced WUE helps plants maintain physiological processes such as photosynthesis, nutrient transport, and cell expansion during periods of limited moisture. As drought frequency and irrigation restrictions become more common, improving water-use efficiency has become an increasingly important strategy for maintaining crop productivity under changing climate conditions.

Through these combined effects, biologicals help plants maintain physiological activity, improve drought resilience, and sustain growth under limited water conditions.

2. Enhanced Nutrient Uptake and Availability

Biologicals improve plant stress tolerance by enhancing the availability, mobilization, and uptake of essential nutrients required for healthy growth and metabolism. Under drought stress, PGPR contribute to plant growth by functioning as biofertilizers that improve nutrient availability and uptake through diverse mechanisms, including biological nitrogen fixation, mineral solubilization, phosphate and potassium solubilization, siderophore production, and iron sequestration, as demonstrated in numerous studies. (3) By increasing nutrient accessibility and utilization, these microbial interactions help plants maintain essential physiological processes, sustain growth, and enhance their ability to withstand environmental stresses such as drought and nutrient limitations.

Figure 3: Plant Growth Promotion Mechanism by PGPB

Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC9958599/

3. Regulation of Plant Hormones

Biologicals enhance plant tolerance to abiotic stress by modulating phytohormone biosynthesis and signalling pathways that regulate growth and stress adaptation. Plant growth-promoting rhizobacteria (PGPR) and other beneficial microorganisms stimulate auxin production to promote root development and improve water and nutrient uptake, while regulating abscisic acid (ABA) levels to optimize stomatal closure and minimize water loss under drought conditions. They also enhance the production of cytokinins and gibberellins, which help sustain cell division, shoot growth, and overall plant development during stress. Some PGPR also produce the enzyme ACC deaminase, which reduces stress-induced ethylene production.

Because excessive ethylene can inhibit root growth during drought and heat stress, lowering ethylene levels helps plants maintain healthier root systems and continue growing under adverse environmental conditions.(4) By maintaining hormonal homeostasis, biologicals enable plants to balance growth with defense responses, thereby improving resilience to drought and other environmental stresses.

Figure 4: Role of PGPR Under Drought Stress

Source: Adapted from The role of plant growth promoting rhizobacteria in plant drought stress responses | BMC Plant Biology | Springer Nature Link

Enhancing Plant Defense Mechanisms:

Biologicals help plants tolerate drought and heat stress by strengthening their natural defence systems. They promote the accumulation of protective compounds such as proline and soluble sugars, helping cells retain water and maintain turgor during dehydration. They also regulate stomatal opening to reduce water loss while supporting photosynthesis. Under environmental stress, plants produce excessive reactive oxygen species (ROS), which can damage DNA, proteins, lipids, and cell membranes if allowed to accumulate. In addition, biologicals enhance antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and peroxidases, which neutralize excess ROS and protect cellular structures. At the molecular level, they activate stress-responsive genes and signalling pathways, enabling plants to adapt more effectively to environmental stress.

5. Improved Soil Health and Microbial Activity:

Biologicals improve soil health by enhancing soil structure, increasing beneficial microbial activity, and supporting nutrient cycling. Many beneficial microorganisms also produce natural compounds, including extracellular polysaccharides (EPS), that help bind soil particles into stable aggregates. Improved soil aggregation enhances pore space, water infiltration, aeration, and water-holding capacity, creating a healthier environment for root growth and beneficial microbial activity. A healthy and biologically active soil retains more moisture, improves aeration, and makes essential nutrients more available to plants. These improvements promote stronger root growth and help plants better withstand drought and heat stress. By enriching soil fertility and maintaining a balanced soil ecosystem, biologicals create conditions that support healthier, more resilient crops.

Figure 5: Role of Biologicals in Sustainable Agriculture

Why Biologicals Matter for Sustainable Agriculture

Biologicals are becoming an essential component of sustainable agriculture because they improve crop productivity while helping reduce reliance on synthetic fertilizers and pesticides. By enhancing nutrient availability, promoting healthy root growth, improving soil fertility, and increasing plant tolerance to environmental stresses such as drought and heat, biologicals help maintain stable yields under changing climate conditions. They also support beneficial soil microorganisms and long-term soil health, making farming systems more resilient, environmentally friendly, and sustainable for future food production.

Although biologicals offer significant benefits, they perform best when integrated with sound agronomic practices, including proper fertility management, irrigation management, crop rotation, and soil health management. Biologicals complement good crop management practices by strengthening natural plant and soil processes, rather than replacing them.

High temperatures can severely affect plant growth by disrupting enzyme activity, reducing photosynthesis, and impairing flowering and fruit development. Heat stress also damages chloroplasts, reduces chlorophyll concentration, decreases the efficiency of photosystem II, and can impair pollen viability, ultimately reducing flowering, fruit set, and grain fill. Biologicals, particularly plant growth-promoting rhizobacteria (PGPR), help plants cope with heat stress by stabilizing cellular proteins and membranes, regulating heat shock protein production, and maintaining photosynthetic efficiency, and enhancing antioxidant activity to reduce oxidative damage. They also support antioxidant activity and improve water and nutrient uptake, enabling plants to maintain normal physiological functions under elevated temperatures.

By enhancing these natural defence mechanisms, biologicals improve plant resilience and support more sustainable, climate-resilient crop production. (5) When integrated with sound agronomic practices, biologicals can complement conventional crop nutrition and crop protection programs while contributing to long-term soil health and agricultural sustainability.

Conclusion:

As climate change continues to increase the frequency and severity of drought, heat, and other environmental stresses, growers are under increasing pressure to produce more food while using resources more efficiently and preserving long-term soil health. Meeting these challenges will require innovative solutions that not only improve crop productivity but also strengthen the resilience of agricultural systems.

Biologicals are becoming an essential part of modern agriculture because they work with nature rather than against it. By improving root development, nutrient availability, water-use efficiency, soil biology, and the plant's natural defence mechanisms, biologicals help crops better withstand environmental stress while supporting healthier soils and more sustainable production systems. When integrated with sound agronomic practices, they provide growers with another valuable tool to improve crop performance and adapt to an increasingly unpredictable climate.

At Nurture Growth Bio Fertilizer, we believe the future of agriculture begins below the soil surface. Our proprietary multi-microbial technology has been developed to harness the power of beneficial microorganisms that naturally improve soil health, nutrient cycling, root development, and plant resilience. Guided by science and validated through research and commercial field trials, our mission is to provide growers with innovative biological solutions that improve crop performance while supporting the long-term sustainability of their land.

As agriculture continues to evolve, the future will belong to farming systems that build healthier soils, stronger plants, and more resilient crops. By investing in soil biology today, growers are investing in the long-term productivity, profitability, and sustainability of agriculture for generations to come.

Blogger Biography:

Dr. Ankita Garkoti is a Senior Science Officer at Nurture Growth Bio Fertilizer. She has over 9 years of experience in Agriculture research and extension. Her areas of specialization encompass Plant Pathology, Microbiology, Plant Protection, Organic farming, Biofertilizers, Organic Fertilizers, and Biocontrol agents.

She holds a Ph.D. in Plant Pathology and a master's degree in Botany with a specialization in Plant Pathology. Her doctoral research involved an in-depth study of lentil wilt and its management through various practices. She has extensive experience in organizing training programs on Organic and Natural farming techniques for farmers, agricultural growers, students and other stakeholders.