Question

Which combination of statements is incorrect for the adaptation in cactus?
This question has multiple correct options.
A. The cactus plant stores water in their stems which carries out photosynthesis and is covered by the cuticle.
B. Spines are modified leaves of the cactus plant, which reduces loss of water through transpiration.
C. The cactus plant has short roots which cannot properly absorb water from the soil.
D. The cactus plants lose a huge amount of water through transpiration so they cannot survive in deserts for a long time.

Answer 1

Hint: Cactus belongs to family Cactaceae. They are native to America. These plants can thrive in extreme temperatures and are resistant to drought. In order to survive in dry climatic conditions, cactus has developed special morphological features.

Complete step by step answer: Cactus is a class of Xerophytes, that is plants adapted to thrive in dry climatic conditions. These plants have evolved to develop morphological features that allow them to conserve water instead of losing them. Let us explore some adaptations as demonstrated by Cactus.
The stem of the cactus is designed to conserve water. it is highly modified to contain specialized cells that store water. This kind stem is known as succulent. The stems are generally green in colour and are capable of performing photosynthesis. There is a waxy coating on the stem that prevents loss of water.
The leaves of the cactus plants are modified into spines. This ensures reduction in the surface area that is exposed to air, thereby reducing the rates of transpiration and evaporation. The branches in cactus are also fewer in number as compared with other plants. This is also a means of reducing the exposed area of the plants.
The stomata on the cactus plants close if there is an indication of water stress. This is achieved by signals sent by roots. The tap roots of the cactus grow deep into the soil for reaching the ground water table of the area. If there is an indication of onset of water stress, the roots send signals up to the plant that facilitate stomatal closure.
Transpiration in cactus plants takes place during the night. Since it is cooler during night than during daytime, the water loss is reduced. Also, these plants convert the carbon dioxide that enters the plant during transpiration into malic acid and stores it. Again, during daytime, the malic acid is converted into carbon dioxide and used up in photosynthesis.
Therefore, we can conclude that cactus stems store water, perform photosynthesis and are covered by a cuticle. The leaves are modified into spines to help reduce transpiration. However, the roots of the cactus plant deep into the soil and absorb water very efficiently. Transpiration in cacti is reduced to prevent water loss.
Therefore, options (c) and (d) are the correct combination of statements.

Note: Cactus is a xerophyte. It generally grows in arid and semi-arid conditions. The plants have adapted to the dry climatic condition by developing various morphological and physiological adaptations. They have their stems covered with a cuticle; leaves modified into spines for reduced rates of transpiration. The root system of the cactus plants is a tap root system that penetrates deep into the soil for reaching the water table. Stem is capable of performing photosynthesis. They are found worldwide and are used as an ornamental plant.