Question

All the leaves of the plant are modified into spines in
A) Orchid
B) Cactus
C) Ruscus
D) Acacia

Answer 1

Hint:There are many plants which have spines in the form of leaves. This can be for protection or for prevention of water loss. Some plants witness modification of their leaves into tendrils for structural support. There are a few plants which have thick leaves for water storage whereas some others are modified to catch and digest insects.

Complete Answer:
>The Orchid plant is usually grown close to the tropics. Its flowers are vividly coloured along with emitting beautiful fragrance. Most of the plants of the Orchid family have round and curved leaves. Their roots have been specially adapted to absorb moisture and dissolved nutrients. As we can see, the Orchid plant does not have modified leaves. Thus, this option is wrong.
>The Cactus plant is native to arid and semi-arid regions. It is distinguished by its ‘spines’ which are the modified versions of its leaves. Its leaves are modified to extremely small-sized spines to minimize the surface area from which water can be lost. Its stem takes up the role of photosynthesis thus allowing it to survive in deserts.

Hence, the Cactus is the correct answer here.

Note:In some Cactus plants, leaves are either absent or reduced. As it is an arid plant, it cannot afford losing water. The Cactus spines are created from some specialized structures which is called Areoles. This is some sort of reduced branch. Through these areoles, the cactus plants are distinguished. Along with the spines, the flowers are risen from the areoles. These flowers are usually tubular and they have multiple petals.