LEAVES.pdf

LEAVES Vital organ Photosynthesis Gas exchange Food Learning Objectives At the end of the lesson, students are expected to: 01 Discuss different leaf types 02 Identify the important parts of leaves 03 Compare a simple leaf to a compound leaf 05 Classify leaves based on thei...

LEAVES Vital organ Photosynthesis Gas exchange Food Learning Objectives At the end of the lesson, students are expected to: 01 Discuss different leaf types 02 Identify the important parts of leaves 03 Compare a simple leaf to a compound leaf 05 Classify leaves based on their margin, shape, & arrangement 06 Compare monocot and eudicot leaves Leaf/Leaves Common: Foliage Leaf Large, flat, and green Trees in Nami Island changes its form per season Spring Summer Autumn “fall” Winter A perfect example of adaptation in plants Other Leaf Types Bud scales Spines Tendrils Storage Carnivorous  For protection Cover and protect developing buds small, tough, waxy, hairy coating Prevent damage Bud scales  For protection Sharp and pointed structures Against herbivores Prevent water loss conserve moisture Spines  For support & stability Wrapping, climbing, or curling at nearby objects Withstand winds and other stress Better access to light Thigmotropism Tendrils  For storage Fleshy and thick Hold large amounts of water (ex. succulents) Survival to arid environments Storage  Carnivorous plants Traps insects for nitrogen acquisition Survival in nutrient poor environments Ex. Venus fly trap, pitcher plant Carnivorous Venus Flytrap Dionaea muscipula External structure of foliage leaves  Leaf Anatomy Lamina No petiole Sessile leaf Compound Leaves Pinnately Palmately Compound Compound  Leaf Margin Phyllotaxy arrangement of leaves on the stem or on a branch of a plant  Leaf Shapes Cordate Hastate Peltate  Peltate © Christa Watters Sagittate  Leaf Venation Vascular Tissues Patterns of veins in the leaf blade  Leaf Venation Monocots Long strap-shaped leaves Larger veins run side-by-side Thin, slender, and flat leaf blade Parallel Venation  Leaf Venation Eudicots/dicots In basal angiosperms and eudicots Occur in a netted pattern called reticulate venation Broader leaf blade Internal leaf structures  Overview Chloroplast Cuticle Palisade Cells Upper Epidermis Spongy Mesophyll Mesophyll Guard Cells Lower Epidermis Stomata Vascular Bundles Cuticle A waxy layer covering the upper epidermis of the leaf, made of a substance called cutin. The cuticle acts as a waterproof barrier, reducing water loss from the leaf's surface.  Upper Epidermis The single layer of cells covering the top surface of the leaf. Provides protection from water loss, UV radiation, and pathogens. It also secretes a waxy cuticle.  Lower Epidermis The single layer of cells covering the underside of the leaf. Similar to the upper epidermis, it provides protection and contains more stomata for gas exchange.  Stomata Microscopic pores on the leaf surface, allow for gas exchange (carbon dioxide intake and oxygen release). Controlled by guard cells, stomata open and close to regulate gas exchange and water loss. Stomata Transpiration Process where water is absorbed by the roots from the soil and transported up through the plant via the xylem vessels. Once it reaches the leaves, water evaporates from the mesophyll cells and exits via the stomata More stomata are present in the lower epidermis More stomata are present in the lower epidermis Water Conservation More stomata are present in the lower epidermis Water Conservation Protection from UV radiation More stomata are present in the lower epidermis Water Conservation Protection from UV radiation Reduced exposure to Pathogens More stomata are present in the lower epidermis Water Conservation Protection from UV radiation Reduced exposure to Pathogens Efficiency in gas exchange Mesophyll The tissue between the upper and lower epidermis of the leaf, responsible for photosynthesis. Contains chloroplasts for capturing sunlight and carrying out photosynthesis. It's further divided into two types of cells. Palisade Mesophyll Tightly packed cells that contain a high number of chloroplasts. They specialized in photosynthesis due to their abundance of chloroplasts for capturing sunlight. Spongy Mesophyll Irregularly shaped cells in the lower region of the mesophyll, containing air spaces between them. Allow for gas exchange within the leaf due to the air spaces. Chloroplasts These are specialized organelles within plant cells containing chlorophyll, the green pigment responsible for capturing sunlight during photosynthesis. Chloroplasts convert sunlight energy into chemical energy (glucose) through photosynthesis.  Vascular Tissues A network of tubes within the leaf, transporting water, nutrients, and sugar throughout the plant. Xylem vessels transport water and minerals from the roots to the leaves. Phloem vessels transport sugar.  References BYJUS. (2018) Transpiration. BYJUS. https://byjus.com/biology/transpiration/ Mauseth, J. D. (2017). Botany : An Introduction To Plant Biology (6th ed.). Jones & Bartlett Learning. Phyllotaxy - NEET Biology Notes. (n.d.). BYJUS. https://byjus.com/neet/phyllotaxy-notes/ Plantid.net.https://plantid.net/Classic/Glossary/Leaf%20Arrangement.htm? AspxAutoDetectCookieSupport=1 Yamaguchi, T., Nukazuka, A., & Tsukaya, H. (2012). Leaf adaxial-abaxial polarity specification and lamina outgrowth: evolution and development. Plant and Cell Physiology, 53(7), 1180–1194. https://doi.org/10.1093/pcp/pcs074  Thank you for listening!