Leaf Shapes and Modifications PDF

# Leaf Shapes ## Section (7) prepared by: Prof. Dr. Galal Eisa Dr. Safaa Mourad ## A. Simple Leaves - **Entire or unlobed**: Blade is undivided - **Example**: Corn and wheat, Duranta and Ficus plant. - **Lobed**: Blade is divided into portions connected by tissue. - **Pinnately lobed**:...

# Leaf Shapes ## Section (7) prepared by: Prof. Dr. Galal Eisa Dr. Safaa Mourad ## A. Simple Leaves - **Entire or unlobed**: Blade is undivided - **Example**: Corn and wheat, Duranta and Ficus plant. - **Lobed**: Blade is divided into portions connected by tissue. - **Pinnately lobed**: Divisions extend from the midrib. - **Example**: Papaver and oak plant. - **Palmately lobed**: Divisions radiate from a single point. - **Examples**: Fig, grape, Castor, Luffa, Hibiscus plant. ## B. Compound Leaves ### 1. Palmately Compound Leaves - Leaflets radiate from a single point at the end of the petiole. - Leaflets directly attached to the petiole. - **Examples**: Aralia, Lupinus. ### 2. Pinnately Compound Leaves - Leaflets arise along the main axis. - **Odd or Imparipinnat compound leaves**: main axis terminates with a single leaflet. - **Example**: Rosa. - **Trifoliate compound leaves**: Compound leaf with only three leaflets. - **Example**: Trifolium (Clover). - **Even-Pinnate or Paripinnate compound leaves**: main axis terminates with a pair of leaflets. - **Example**: Cassia acutifolia. - **Bipinnately Compound leaves**: leaflets are further divided into pinnules. Pinnules is carried on second-class axles. - **Example**: Poinciana plant. - **Tripinnately Compound leaves**: leaflets are divided multiple times. Pinnules is carried on third-class axles. - **Example**: Certain Fern. ## Venation - **Venation**: refers to the arrangement of veins within a leaf blade. These veins are responsible for transporting water and nutrients from the roots to the leaf and for transporting sugars produced by photosynthesis to other parts of the plant. - **Types of Venations**: - **Reticulate Venation**: - In reticulate venation, the veins form a network of interconnected branches. This type of venation is characteristic of dicotyledonous plants and some of monocotyledonous. - **Reticulate Pinnate Venation**: - A single, prominent midrib runs along the length of the leaf, and smaller veins branch off form it, forming a feather-like pattern. **Examples**: ficus and rose leaves. - **Reticulate Palmate Venation**: - Several main veins radiate from a single point at the base of the leaf, resembling a palm. **Examples**: grape and castor bean leaves. - **Parallel Venation**: - In parallel venation, the veins run parallel to each other along the length of the leaf. This type of venation is common in monocotyledonous plants and some dicotyledonous. - **Parallel basal Venation**: - Multiple main veins run parallel to each other from the base to the tip of the leaf and parallel to the midrib. These veins may converge at the tip or may be connected by smaller, transverse veins. **Examples**: corn, wheat, and barley leaves. - **Parallel costal Venation**: - A single, prominent midrib runs along the length of the leaf, and smaller veins branch off from it at right angles. These smaller veins run parallel to each other. **Examples**: banana leaves. ## The Role of Venation - **Transport of Water and Nutrients**: Veins transport water and minerals from the roots to the leaves. - **Transport of Sugars**: Veins provide structural support to the leaf blade, helping it to maintain its shape and resist damage from wind and rain. - **Structural Support**: Veins transport sugars produced by photosynthesis from the leaves to other parts of the plant. - **Gas Exchange**: Veins are often associated with stomata, which are tiny pores that allow for gas exchange between the plant and the atmosphere. ## Leaf Modifications - Leaves, the primary photosynthetic organs of plants. The leaf or part of it can change into another form or modifications to adapt to various environmental conditions and perform specialized functions. - **Protective Modifications**: - **Spiny Leaves**: - Reduce transpiration - Protect against herbivory - **Examples**: The basal leaflets of the individual pinnate compound leaf in the Date palm, prickly pear, cactus, Citrus aurantium and asparagus. - **Climbing Modifications**: - **Tendril Leaves**: - Aid in climbing structures - **Examples**: Tropaeolum, bean, pea. - **Storage Modifications**: - **Storage Leaves**: - Store water or food - **Examples**: Bulbs, succulent plants (like cacti). - **Reproductive Modifications**: - **Flowering Leaves**: - Specialized for sexual reproduction - Bear reproductive structures (stamens and pistils). - **Vegetative Reproductive Leaves**: - Produce adventitious buds for asexual reproduction - **Example**: Kalanchoe pinnata. - **Secretory Modifications**: - **Sac Leaves**: - Secrete nectar to attract pollinators - **Examples**: Delphinium plant. - **Insectivorous Modifications**: - **Insectivorous Leaves**: - Trap and digest insects to obtain nitrogen - **Examples**: Drosera, Dionaea and the pitcher plant. - **Convert the inner flower leaf to carpel where it is like a bag usually composed of the ovary style, and stigma.**