Plant roots in varying soil moisture levels.

Thirsty Plants? How Soil Moisture Affects Their Water Uptake

Avery Sinclair in Science & Nature August 2025 • 4 min read.

"Uncover the secrets of how plants adapt to varying soil moisture levels and what it means for agriculture and ecosystem health."

Plants, like all living things, require water to survive. The process of transpiration, where plants release water into the atmosphere, is fundamental to this exchange. Understanding the factors that control transpiration is crucial for predicting water transfer across ecosystems and optimizing agricultural practices.

While atmospheric conditions and above-ground plant properties like leaf area and stomatal conductance are known to influence transpiration rates, the availability of water in the soil plays a critical role. When soil moisture is abundant, plants can easily take up water. However, as the soil dries, the process becomes more complex, impacting plant water potential and overall health.

A new study investigates the intricate relationship between leaf water potential, transpiration rate, and soil water potential under heterogeneous soil conditions. By combining experimental measurements with root water uptake models, researchers are gaining valuable insights into how plants adapt to drought and the role of hydraulic lift in water redistribution.

Unpacking Soil Water Potential: What It Means for Plant Health

Plant roots in varying soil moisture levels.

Soil water potential refers to the energy required for a plant to extract water from the soil. It encompasses matric potential (due to capillary forces) and osmotic potential (due to dissolved salts). When soil is saturated, water potential is high, making it easy for plants to absorb water. As the soil dries, the water potential decreases, increasing the energy plants must expend to obtain water.

The relationship between leaf water potential (the water potential in a plant's leaves) and transpiration rate is complex, especially when soil water potential isn't uniform. In reality, soil moisture is rarely consistent throughout the root zone. The topsoil tends to dry out faster due to higher root density and water evaporation. As a result, plants must adapt to these varying conditions.

Experiment Setup: Researchers grew lupines in sandy soil, dividing it into two layers separated by a coarse sand barrier. This setup allowed roots to grow through but limited water movement between layers.
Three Scenarios: They tested three moisture scenarios: wet-wet (both layers wet), dry-wet (top layer dry, bottom wet), and dry-dry (both layers dry).
Measurements: They measured transpiration rates and leaf water potential using a root pressure chamber technique, which gauges the suction force in the leaves.

The results showed a linear relationship between transpiration and leaf water potential in all scenarios. However, when the topsoil dried out, the soil-plant system's conductance (its ability to transport water) decreased significantly. This highlights how drying soil impedes water uptake and affects plant physiology.

The Bigger Picture: Implications for Agriculture and Beyond

Understanding the dynamics of plant water uptake is crucial for sustainable agriculture and ecosystem management. As climate change brings more frequent and severe droughts, it becomes increasingly important to develop strategies that enhance plant resilience. These strategies may include selecting drought-tolerant crop varieties, optimizing irrigation techniques, and promoting soil health to improve water retention. By continuing to unravel the complexities of plant-soil interactions, we can better safeguard our food security and preserve the health of our planet.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.advwatres.2018.12.009, Alternate LINK

Title: Measurements And Simulation Of Leaf Xylem Water Potential And Root Water Uptake In Heterogeneous Soil Water Contents

Subject: Water Science and Technology

Journal: Advances in Water Resources

Publisher: Elsevier BV

Authors: Faisal Hayat, Mutez Ali Ahmed, Mohsen Zarebanadkouki, Gaochao Cai, Andrea Carminati

Published: 2019-02-01

Everything You Need To Know

What is transpiration, and what factors influence it?

Transpiration is the process where plants release water into the atmosphere. It's a fundamental exchange influencing water transfer across ecosystems. Factors such as atmospheric conditions, leaf area, stomatal conductance, and most importantly, soil moisture, control transpiration rates. Insufficient soil moisture complicates the process, impacting a plant's water potential and overall health.

What does soil water potential mean for plant health, and how does it affect water uptake?

Soil water potential is the energy a plant needs to extract water from the soil, comprising matric potential (capillary forces) and osmotic potential (dissolved salts). High soil water potential in saturated soil makes water absorption easy, while low soil water potential in dry soil increases the energy plants expend to obtain water.

How did the researchers investigate plant water uptake under different soil moisture conditions?

The study used lupines grown in sandy soil divided into two layers by a coarse sand barrier, allowing root growth but limiting water movement. They tested three scenarios: wet-wet (both layers wet), dry-wet (top layer dry, bottom wet), and dry-dry (both layers dry). They measured transpiration rates and leaf water potential, revealing how drying topsoil significantly reduces the soil-plant system's ability to transport water.

What happens to a plant's ability to transport water when the topsoil dries out, and what are the implications?

When the topsoil dries, the soil-plant system's conductance decreases significantly. This means the plant's ability to transport water from the soil to its leaves is reduced. The linear relationship between transpiration and leaf water potential is affected, indicating that the plant needs to work harder to extract water, impacting its overall physiology and potentially leading to stress or reduced growth.

Why is understanding plant water uptake important, and what strategies can enhance plant resilience in agriculture and ecosystem management?

Understanding plant water uptake is vital for sustainable agriculture and ecosystem management, especially with increasing droughts due to climate change. Strategies include drought-tolerant crops, optimized irrigation, and improving soil health to enhance water retention. Further research into plant-soil interactions is crucial for safeguarding food security and preserving planetary health. Other strategies not mentioned include the use of antitranspirants and understanding plant hormone responses to drought.