Modification 6. In others, leaves form 3, 4, 5 or several rows called orthostichies. The leaf apices of Gloriosa superba (vern. 6. a day ago. Phloem lies towards the lower side while xylem is found towards the upper side. Phloem consists of sieve tubes and companion cells. Instead petiole and part of the rachis become flattened into sickle-shaped structure for performing the function of food synthesis (Fig. Such a flattened petiole which carries out the functions of the lamina is called phyllode. They are modified into sepals, petals, stamens and carpels to take part in sexual reproduction. Importance. They resemble the nails of a cat and hence the names of the plant, the hooks cling to the bark of the supporting tree very firmly and allow the plant to climb up. The vascular bundles are almost rounded. The outer walls are cutinised. The leaflets (pinnae or pinnules) differ from the whole leaves in the absence of axillary buds, basal stipules and origin in the same plane. The leaf is the site of photosynthesis in plants. 5. Why does plant cell possess large sized vacuole? Characteristics of Leaf 3. As the chloroplasts are more abundant in the compact palisade mesophyll cells than the loosely arranged spongy mesophyll cells, the upper surface of the leaf appears deeper green as compared to the lower surface. 10. Leaves are between 7 and 15 centimeters long, and the axis of each leaf adorns a solitary flower. It is chlorenchymatous. 5.61): In Wild Pea (Lathyrus aphaca, Fig. The palmate compound leaf is one in which the petiole bears leaflets at the tip like the fingers of the palm. The vascular bundles are conjoint, collateral and closed. Functions 7. What is the reserve food material in red algae? Our mission is to provide an online platform to help students to share notes in Biology. Therefore, the two surfaces are equally green (Gk. Cyclic phyllotaxy includes both opposite and whorled types of phyllotaxy. 3. Edit. Due to their peculiar thickening the guard cells can create a pore in between them when they get swollen due to endosmosis. 3. Save. Leaf base may be broadened to enclose the stem. Xylem consists of vessels, tracheids, xylem parenchyma and a few xylem fibres. marciaksmith. Each stoma or stomate has a narrow pore bounded and controlled by two small specialised kidney-shaped epidermal cells called guard cells. The lamina can have various types of incions, which may reach upto half (-fid), more than half (-partite) or near the base of midrib (-sect). The leaves have chlorophyll for trapping sun energy. Stipules fuse to form a sheath or ochrea around the stem, e.g., Rumex, Polygonum. (iii) They are borne on the stem at the nodes. Gaajar). (xi) Leaf bears abundant stomata for exchange of gases. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? The principal veins converge towards the apex of the lamina, e.g., Zizyphus, Smilax. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? 5.58 C). They are whitish or brownish, small, dry and membranous leaves which do not take part in photosynthesis. Stipules fused with petiole, e.g., Rose, Groundnut. The inner and the radial walls of the epidermal cells are thin. The lower surface is correspondingly called outer, abaxial or dorsal surface. They are of the following types (Fig. 5.59 D), e.g., Paris quadrifolia; Marsilea also seems to have quadrifoliolate leaves (Fig. Vascular strands represented by veins conduct water and minerals from stem to leaves in their xylem and transport organic materials from leaf blade to stem in their phloem. In Salvinia one leaf of each node is changed into roots that act as balancers for floating. What are the general characters of bryophytes? Dhania), Carrot (vern. Small, free, green outgrowths, e.g., Shoe-flower (Hibiscus rosa-sinensis). The mesophyll cells enclose intercellular spaces which are, however, smaller than those of the typical spongy parenchyma. 3. They are called bulliform or motor cells. Xylem is formed of vessels, tracheids and xylem parenchyma. The leaves are covered by mucilage. The close relatives of Citrus possess trifoliolate leaves (Aegle marmelos, Fig. Sahinjana, Soanjana), Meha azedarac (vern. Share Your PPT File. Leaves possess minute pores called stomata. (i) Pinnate or Unicostate Reticulate Venation: The lamina has a single principal vein or midrib which extends from its base to apex. (viii) A leaf is differentiated into three parts – leaf base, petiole and lamina. (vii) unfolding of the young leaves by means of motor or bulliform cells. In this article we will discuss about:- 1. Gaseous exchange takes place through stomata. 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