Leaves PDF - Our Lady of Fatima University

Leaves Pharmaceutical Botany with Taxonomy (PBOT111) Patrick Joel F. Bicaldo, RPh, MSPharm (cand.) Faculty member College of Pharmacy, Antipolo City Campus ver. PJFB24-25 LEARNING OBJECTIVES At the...

Leaves Pharmaceutical Botany with Taxonomy (PBOT111) Patrick Joel F. Bicaldo, RPh, MSPharm (cand.) Faculty member College of Pharmacy, Antipolo City Campus ver. PJFB24-25 LEARNING OBJECTIVES At the end of this module, the students should be able to: 1. Describe the stems and understand their classification, internal and external structures, functions, and importance in the economy. 2. Understand the different practical applications of knowledge of stem structure and physiology. 3. Describe the leaves and understand their classification, internal and external structures, adaptations, functions, and importance in the economy. Outline ▪ Leaves ▪ External and internal structures ▪ Other leaf types and modifications ▪ Morphology and anatomy of other leaf types Leaves ▪ Generally expanded and flattened green structure growing out of the nodes of the stem The main organ for photosynthesis. Most leaves are usually green due to chlorophyll in the leaf cells. However, some leaves may have different colors caused by other plant pigments that mask the green chlorophyll. External structure of the leaves Parts of a Parts of a Monocot Leaf Dicot Leaf External structure of the leaves PARTS OF A MONOCOT LEAF ▪ Leaf sheath: the support of the leaf, which may completely envelope the stem of a small flap of delicate tissue extending upward called the ligule ▪ Leaf blade: thin expanded portion above the sheath ▪ Ligules: are membranous or hairy tissues located at the junction of the leaf blade and leaf sheath ▪ Auricles: are slender extensions of the collar and are located at the junction of the leaf blade and leaf sheath External structure of the leaves PARTS OF A DICOT LEAF Leaf blade ▪ Thin, flattened, usually green expanded part of the leaf ▪ Variable external features are its overall shape, apex, margin, and bas Varieties of leaf blade or lamina Based on Shape Based on Apex Based on Margin Based on Base Varieties of leaf blade or lamina Based on Shape Based on shape Linear: long and slender Example: Grasses Cordate: heart-shaped Example: Gabi, Mayana Ovate: egg-shaped Example: Eucalyptus, rose Varieties of leaf blade or lamina Based on Shape Based on shape Deltoid: triangular Example: Cottonwood, Louisiana Reniform: kidney-shaped Example: Pink pyrola, takip-kohol Ovate: disk-like Example: Spinach, barbosella Varieties of leaf blade or lamina Based on Shape Based on shape Flabellate: fan-like Example: Gingko biloba Cuneate: wedge-like Example: Tsaang gubat Varieties of leaf blade or lamina Based on apex Based on apex Acute: sharp point Example: Mangifera indica Acuminate: long, slender tail Example: Ficus religiosa Cuspidate: long, sharp, spiny point Example: Phoenix sylvestris Obtuse: blunt, rounded end Example: Cassia obtusifolia Truncate: cut transversely straight Example: Bauhinia anguina Varieties of leaf blade or lamina Based on apex Based on apex Retuse: obtuse with a shallow notch Example: Pistia stratiotes Emarginate: deep notch Example: Bauhinia spp. Mucronate: short point Example: Calotropis gigantea Cirrhose: tendril-like structure Example: Gloriosa superba Varieties of leaf blade or lamina Based on Margin Based on margin Varieties of leaf blade or lamina Based on margin Entire Even and smooth, ex: Ficus benghalensis Repand Wavy, ex: Polyalthia longifolia Serrate Sharp, small teeth, ex: Rosa serrulate Dentate Teeth project outwards, ex: Nymphaea nouchali Varieties of leaf blade or lamina Based on margin Crenate Teeth are rounded, ex: Bryophyllum Ciliate Fine projecting hair, ex: Corchorus olitorius Spinous Projecting spines, ex: Argemone Lobed Many lobes, ex: Ranunculus Varieties of leaf blade or lamina Based on base Connate Auriculate When the basal lobes of the two opposite leaves When leaf base looks like a small ear-like lobe fuse together after completely clasping together (auricle) on either side of the petiole and the and looks like one leaf, the stem passing through auricles are separated by a narrow sinus. the center of leaf Example: Calotropis procera Example: Canscora Varieties of leaf blade or lamina Based on base Amplexicaul Perfoliate The auriculate leaf base completely When the basal lobes of the leaf lamina fuse together Clasps the stem. after completely clasping the stem as if the stem has pierced the leaf Example: Bupleurum Variation of Leaves Variation in Leaf 1. Leaf blade configuration Structures 2. Venation 3. Phyllotaxy Variation in Leaf 1. Dorsiventral or Bifacial leaves Orientation 2. Isobilateral or Equifacial leaves Variation in Leaf Structures Leaf Blade Configuration Simple leaf The blade consists of only one piece The blade is either completely undivided or has lobes, but the separation does not reach the midrib. Example: Banana Variation in Leaf Structures Leaf Blade Configuration Compound Leaf The blade is divided into segments called leaflets or pinnae; the stalk of each leaflet is known as a petiolule. Types of compounds leaf: palmately compound leaf, pinnately compound leaf, and double compound leaf. Variation in Leaf Structures Leaf Blade Configuration Types of Compound Leaf 1. Palmately Compound Leaf Leaflets branch from the petiole Example: Horse chest nut 2. Pinnately Compound Leaf Leaflets branch from the midrib Example: Scrub Hickory 3. Double Compound Leaf Leaflets branch from the veins Example: Honey Locust Variation in Leaf Structures Venation Arrangement of Veins Venation arrangement of Veins A. Netted or Reticulate Venation: veins branch profusely and form a network over the blade; found in dicots. Pinnately netted: veins and their branches spread out in all directions from the midrib, the continuation of petiole. Palmately netted: several midribs arise from the top of the petiole and spread fan-like through the blade. Radiately netted: several midribs arise from the tip of the petiole like the ribs or spokes of an umbrella and then breaks up into smaller veins; found in leaves where petiole is more or less at the center of the blade. Variation in Leaf Structures Venation Arrangement of Veins Venation arrangement of Veins B. Parallel venation: veins do not form a network; found in monocots. Pinnately parallel: with veins parallel to the midrib. Longitudinal parallel: with the veins at acute or right angles to the midrib. Variation in Leaf Structures Phyllotaxy Phyllotaxy: system of leaf arrangement on the stem Alternate or Spiral Only one leaf at each node Opposite Two leaves located opposite each other at a node Variation in Leaf Structures Phyllotaxy Phyllotaxy: system of leaf arrangement on the stem Whorled or Verticillate Three or more leaves located around the node Fasciculate Two or more leaves located only on one side of the node Variation in Leaf Orientation Dorsiventral or bifacial leaves Leaves are horizontally oriented The upper or ad-axial surface receiving direct sunlight Isobilateral or Equifacial leaves Leaves are vertical The two surfaces receiving direct sunlight Internal Structure of Leaves Leaf blade Dorsiventral leaves Epidermis Midrib Mesophyll Upper or lower epidermis Isobilateral leaves Epidermis Collenchyma Mesophyll Parenchyma Vascular tissues Vascular bundles Internal Structures of Leaves LEAF BLADE: DORSIVENTRAL LEAVES Epidermis Upper and lower outermost layer of more or less rectangular cells whose outer wall are cutinized. Randomly scattered at random are pores or stomatal apertures associated with a pair of kidney-shaped chlorophyllous cells, the guard cells Mesophyll Photosynthetic parenchymatous region between the upper and lower epidermis Due to presence of chlorophyll, cells are called chlorenchyma Internal Structures of Leaves Parts of Mesophyll Palisade Parenchyma Located below the upper epidermis Cells are elongated and closely arranged with their long axes perpendicular to the epidermis Main site of photosynthesis Internal Structures of Leaves Parts of Mesophyll Spongy Parenchyma Located on the lower part of the mesophyll with irregularly-shaped and loosely-arranged cells. Primary function is to allow diffusion of gases throughout leaf’s interior Internal Structures of Leaves Parts of Mesophyll Vascular Tissues The vascular bundles or veins of the leaf Each bundle surrounded by thin- walled cells called bundled parenchyma or thick-walled cells called the bundle-sheath Xylem occupies the upper part of the bundle and phloem occupies the lower part of the bundle Internal Structures of Leaves LEAF BLADE: ISOBILATERAL LEAVES Internal Structures of Leaves LEAF BLADE: ISOBILATERAL LEAVES Epidermis Similar to dorsiventral leaves Mesophyll Spongy layer occurs between two palisade layer located beneath the upper epidermis and above the lower epidermis Vascular tissues Same as dorsiventral leaves Internal Structures of Leaves MIDRIB Collenchyma cells Inner to the epidermis Parenchyma cells With isolated groups of sclerenchyma inner to the parenchyma Vascular bundle Occupies the center of the midrib which may be circular or crescent-shaped in cross section If circular, the phloem surrounds the xylem If crescent-shaped, the xylem is towards the upper portion and the phloem is towards the lower portion of the bundle Leaves Adaptations The thickness, shape, and size of leaves are adapted to specific environments. Coniferous plant species that thrive in cold environments, like spruce, fir, and pine, have leaves that are reduced in size and needle-like in appearance. These needle-like leaves have sunken stomata and a smaller surface area: two attributes that aid in reducing water loss. Leaves Adaptations In hot climates, plants such as cacti have leaves that are reduced to spines, which in combination with their succulent stems, help to conserve water. Many aquatic plants have leaves with wide lamina that can float on the surface of the water, and a thick waxy cuticle on the leaf surface that repels water. Functions of the Leaves Principal or Main Functions Photosynthesis Transpiration Functions of the Leaves Specialized or Modified Functions Support Example: Tendrils (Garlic vine), hooks (rattan), and supporting leaf bases (banana) Aeration Example: enlarged petioles (water hyacinth) Absorption Example: Thin, uncutinized epidermis (digman), insectivorous leaves (pitcher plant, venus fly trap). Functions of the Leaves Specialized or Modified Functions Attraction of Pollinators Example: Brightly colored leaf blades (Bougainvillea, Dona Aurora), Petalloid bracts (Anthurium, Calla lily) Reproduction Example: Adventitious buds at the certain parts of the leaves (Kataka-taka) Functions of the Leaves Specialized or Modified Functions Protection Example: Bud scales (rubber plant), motile leaves (makahiya), and leaves reduced to spines (cactus) Storage Example: Fleshy, thickened blades (sabila), bulbs (onion, garlic) Additional photosynthesis Example: Expanded leaflike petiole (Pomelo), Expanded leaflike stipule (Rose) Economic Importance Food source like cabbage, lettuce, spinach, celery, etc. Fiber source like hemp, rami, abaca Tea leaves are used to make beverages Tobacco leaves are used in cigarette industry Some drugs are obtained from the leaves Used as flavoring like wintergreen, peppermint, and spearmint References Guerrero, Jonathan Jaime. General botany with Taxonomy: text-workbook.. Educational Pub. (2015) Mauseth, J. D. (2016). Botany. Jones & Bartlett Publishers. This presentation may not be modified or redistributed in whole or in part without permission from Our Lady of Fatima University, College of Pharmacy. THIS IS NOT FOR SALE OR DISTRIBUTION.