Food & Climate 

Basics

Plants and the environment 

Plants are very sensitive to storms, droughts and floods, as they interact with the environment directly by exchanging energy and water. These events can have strongly negative effects on crop yields. We will see how plants are affected by temperatures, humidity or precipitations.

One of the most important contributions of plants to the environment is the production of Oxygen (O₂)  and absorption of (CO₂) from the atmosphere as a result of  Photosynthesis. This is the basic process for plants life.

But plants also affect and change their surroundings making them more suitable for living.

You can see in this picture some of the other ways through the ones plants interact with the environment, being affected by light, temperature, water and winds, but also modifying the environment around them by releasing water to cool the air around, digging into the soil to make it suitable for their roots and other animals or just decreasing the speed of the wind .

As you know plants need water to live and grow but the effects of high temperature threaten the availability of water and yield. Plants in the early stages of development (young plants) are especially vulnerable to extreme weather.

Let´s see now which are some of the interaction mechanisms and how do plants react to wheather events such as heat, floods or droughts. 

High Temperature

Higher temperatures affect crops directly by increasing the evaporation rate, just like high temperatures make you sweat. Plants have very small pores, called stomata, spread over the leaves, which are the most important mechanism for the regulation of water inside and outside the plant. In the picture you can appreciate the structure of these stomata, they are composed by two guard cells which open or close this pore depending on the plant needs of water.This way, during dry periods, they will be closed so that the plant does not lose too much water and they will be opened during periods with normal humidity.

Each kind of plant has different structural characteristics and so they don't all grow best in the same range of temperatures, when the optimal temperature values of a particular plant are exceeded, they tend to respond negatively, resulting in a drop in yield. Most plants are very sensitive to high temperatures altough this also varies depending on the age of the plant and its capability to stand adverse situations.

Higher temperatures also make the soil less capable to retain water as it evaporates very fast, this also affects plants as the soil is their main source of water.

Precipitation

Precipitation, is the primary source of soil moisture, and probably the most important factor determining the productivity of crops. A change in climate can cause changes in  precipitation (decrease or increase).

Roots are one of the main ways plants have to get water from the environment. These are the parts of the plant that grow deep into the ground searching for water. In many parts of the world there are plants that have much longer roots than trunks and branches, and sometimes a bush that is only around 30 cm high can have roots that get as deep as 2 meters in the soil. This happens in places where there is not much rain along the year, like deserts or very arid regions.

As you can see in this picture roots expand and spread fine threads so that water can be absorbed more easily and in different places at the same time, the more threads a plant has, the easiest it is for it to get more water and to reach further places.

Dry periods may have negative effects on plants growth, but this always depends on the capacity the plant has to expand its roots and the amount of water kept in the soil.

On the other hand some types of weather events may damage plants, this is the case of high humidity, frost, and hail which are harmful for differnt types of crops.

High temperatures are normally accompanied by dry periods, which both have negative effects on plants. Roots run out of water to absorb from the soil and stomata have to close in order not to loose more water, this causes the temperature of the plant to rise causing sometimes serious damages. When plants are struggling because high temperatures or lack of water they are said to be under stress.

Excessively wet years, on the other hand, may cause yield declines due to waterlogging (there is too much water and the plant DROWNS or dies because its roots ROT in water)

Intense bursts of rainfall may damage younger plants because of the hard impacts of water and this can also favour soil erosion.

Author:  Marta Moneo and Ana Iglesias- Universidad Politécnica de Madrid - España
1. Scientific reviewer: Alex de Sherbinin - CIESIN, Columbia University - USA
2. Scientific reviewer: Lily Parshall - Goddard Institute for space studies, Columbia University - USA
Educational reviewer: Emilio Sternfeld - Colegio Virgen de Mirasierra - España
Last update: 12/05/2004