Plants in arid environments typically have fewer and smaller vessels compared to plants in moist environments because of their adaptation to conserve water. The size and number of vessels, known as xylem, in plants are directly related to water transport.
Plants have a network of vessels that transport water from the roots to the leaves. In moist environments, water is readily available, so plants can afford to have larger vessels, which enables them to transport water more efficiently. Larger vessels have a higher capacity for water transport, allowing plants to absorb more water and maintain their hydration.
On the other hand, in arid environments where water is scarce, plants need to be more efficient in their water usage. Having smaller vessels helps plants reduce water loss due to evaporation from their leaves, a process known as transpiration. Smaller vessels also help to slow down water movement, allowing plants to retain water for a longer period and survive under drought conditions.
The adaptation to have fewer and smaller vessels is known as xeromorphy, and it is an essential feature for the survival of plants in arid environments. It allows them to maximize water absorption and minimize water loss, ultimately increasing their chances of surviving in harsh conditions with limited water availability.