Question

how does epidermis of xerophytic plants different fromthat of non xerophytic plants

Answer 1

Xerophytes-Plants with special characteristics such that they can survive in climates with a pronounceddry phase are called xerophytes. Plants which can grow in dry habitats or xeric conditions arecalled as xerophytes.
Characters of xerophytes;
1.Leaf size is reduced.2.Thickening of cuticular covering on leaves and stems.3.Leaves are protected by hairs.4.Presence of sunken stomata that are protected by enlarged guard cells.Xerophytes are classified as :
1.Ephemeral annuals: Found in arid zones. They are draught escapers.2.Succulents: These xerophytes have succulent, fleshy plant parts that function for water storagewhich is an adaptation against dry and xeric conditions. e.g.,
a.Opuntia- Stem fleshy, green leaf like and covered with spines
b.Aloe- Leaves succulent, succulent, store gum and mucilage. Stem is thick and reduced. Leaf lamina smooth, shining, margin slightly serrate with sharp edges like spines.
c.Agave-Leaves large with a waxy coating. Store mucilage and water, lamina with serrate marginwith pointed ends just like spines.
3.Non-succulents: These are draught resistant plants. They do not have water storage tissue but areable to withstand critical dry conditions. Leaves are either reduced to scale like structure or theyare thick coriaceous and covered with waxy coating. e.g.
a.Casuarina- Stem with ridges and furrows, leaves scaly, small, ephemeral.
b. Nerium- Root system well developed, stem branched, leaves narrow, linear, long and leathery.
c.Calotropis- leaves are thick and leathery, waxy white cutinisation to reduce transpiration which isan adaptation against xeric conditions.Anatomy of xerophytes:T.S. of  Nerium leaf (non-succulent xerophyte):Epidermis: Upper and lower epidermis multiseriate, cells are compact, isodimetric and colourless,epidermis covered by thick cuticle, sunken stomata on the lower epidermis. A number of trichomes develop from the bordering cells and remain projected within the stomatal pit.Mesophyll: It is distinguished in palisade and spongy cells. Spongy cells are located in betweenpalisade cells. Shhaeraphids are scattered within the mesophyll cells.Vascular bundle: Conjoint, collateral and closed type, xylem and phloem cells aresurrounded by parenchymatous bundle sheath.  2Adaptive anatomical features on Nerium leaf:
1.Presence of sunken stomata on lower epidermis.
2.Presence of distinct stomatal pit with a good number of trichomes to reduce water loss.
3.Presence of sphaeraphids (Calcium oxalate crystals)T.S. of  Aloeleaf (Succulent xerophyte):Epidermis: Single layered with thick cuticleChlorenchyma: Several rows of chlorenchyma with abundant chloroplasts.Vascular bundles: Well developed and arranged at the periphery, xylem is towards centre.
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