Cactus leaves are modified, because they're characterized by smaller surface areas. Ma'am as in the class we have studied the venation of leaves so in cactus as you know that the leaves are modified into spines or thorns so for example i am explaing a child that the leaves having parallel venation will have fibrous roots and the leaves having reticulate - Science - Getting to Know Plants Thorns, Spines and Prickles Cactus spines Cactus spines are usually modified leaves or shoots located in the axil of a leaf. Why leaves of desert plants are modified into thorns? Cacti have adapted to the harsh conditions they live in by developing areoles instead of branches and spines instead of leaves. Cactus spines are actually heavily modified leaves, although they don’t have any of the same structures that are found in normal leaves and are completely inert. A group of spines is termed an areole. Spines for Defence: The non-photosynthetic leaves of cacti have become modified for defence. The leaf-apex in date-palm, dagger plant (Yucca) etc., is so modified, while in plants like prickly or Mexican poppy (Argemone), Amercian aloe (Agave), Indian aloe (Aloe), etc., spines develop on the margin as well as at the apex. The grow, function and then die without sustaining new growth. Soft, broad leaves might be good at photosynthesis, but they lose a lot of water due to evaporation. Those cactus plants that have modified leaves have them as thorns, spines, spikes, quills, prongs or bristles. What is the function of thorns? Numerous plants have spines of course, but in cacti, spines occur in clusters in the axil of leaves, even though the leaves are usually microscopic. honeylocust. In deserts, that is something that plants should avoid, so that they can store water. Tendrils: In peas the terminal leaflet of the leaf has become modified into a tendril for climbing. Cactus Spines Are Modified Leaves. Most cactus morphologists have concluded that cactus spines are either modified leaves or modified bud scales (the difference is inconsequential because bud scales themselves are modified leaves). 4.25) the minute leaves of the axillary bud are modified into spines. Cactus spines occur in clusters in the axil of leaves. Plants lose water through their leaves. 6. Thus, in prickly pear (Opuntia; fig. Complete the given analogy. above-ground roots arising from the stem that can grow through the air and extend down into the soil ~provide extra absorptive capacity and anchorage/stability for the plant ... What kind of modified stem are thorns? These new leaves were good at two things: avoiding water loss and protecting the plant (On this topic, I wrote a post on why cacti adapted to have spines instead of leaves). Cactus spines are also known as modified bud scales, which also are modified leaves. 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