Functions of the Leaves. Is this an example of necrosis or apoptosis? Describe the internal structure and function of a leaf; Key Points. The central pores/apertures are called stomata. Ans. Our mission is to provide an online platform to help students to share notes in Biology. Scale leaves are common on underground stems where they cover and protect the axillary buds under unfavourable conditions. Spongy mesophyll – Layer of parenchyma tissues loosely arranged to facilitate movement of oxygen, carbon dioxide, and water vapor. Q1. The leaf epidermis contains many stomata. It occurs mostly through stomata, but sometimes it also takes place through cuticle and lenticels. Lamina: Also known as leaf blade. Leaves that do not have a petiole and are directly attached to the plant stem are called sessile leaves. Stomata are generally more numerous on the underside of leaves. This trap-door entrance allows aquatic animalcules to pass in, but never to come out. (xi) Leaf bears abundant stomata for exchange of gases, (xii) It is the major seat of transpiration. When young the mouth of the pitcher remains closed by its lid which later on opens and stands erect. They are adapted for photosynthesis by having a large surface area, and contain openings, called stomata to allow carbon dioxide into the leaf and oxygen out. Diversity in roots and shoots enables plants of different species to live together in the same environment without directly competing for resources. When the two guard cells are turgid (swollen with water), the stoma is open, and, when the two guard cells are flaccid, it is closed. This paper attempts to provide a framework within which some of this diversity can be explained. Most of these are found on the lower side of the leaves. Disclaimer Copyright, Share Your Knowledge The base of the leaf is the portion where the petiole comes out to attach the leaf to the rest of the plant, and the apex is the other end – the tip of the leaf. The digestive agent, secreted by glands, is trypsin which helps in digesting the proteins. A waxy cuticle covers all aerial surfaces of land plants to minimize water loss. The stomata are on the shady side of the leaf and out of the direct sunlight. Guard cells work to control excessive water loss, closing on hot, dry, or windy days and opening when conditions are more favourable for gas exchange. A stoma (singular for stomata) is surrounded by two types of specialized plant cells that differ from other plant epidermal cells. Q.2. …flotation devices such as gas-filled stomata and intercellular spaces hold them upright and enable them to grow toward the water surface and obtain sufficient sunlight for photosynthesis. Ans. Stomata open and close to allow the intake of carbon dioxide and the release of oxygen. The leaves modified into thorns and spines (e.g., in Berberis, Aegle), give protection to the plants from animals. The morphological nature of such spines can be pointed out by the presence of a bud in their axis. Before sharing your knowledge on this site, please read the following pages: 1. In bladderwort (Utricularia) the leaves are very much segmented and they simulate roots excepting that they are green in colour. Leaves that do not have a petiole and are directly attached to the plant stem are called sessile leaves. 3. In the pitcher plant (Nepenthes) the leaf becomes modified into a pitcher. Leaves are collectively referred to as foliage, as in "autumn foliage". Phyllode: In some species of Australian Acacia the lamina of the leaf is absent but the petiole is so … Links the leaf is more or less slender and flexible the leaflets themselves are attached to plant! 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