Plant Biology Notes PDF

 Basic Root Study A single root consists simply of a cylindrical axis with a root apex (commonly called root tip) consisting of the root apical meristem. This root apex is not very long (e.g., ≤1cm). The root apex consisting of the root apical meristem, juvenile cells derived...

 Basic Root Study A single root consists simply of a cylindrical axis with a root apex (commonly called root tip) consisting of the root apical meristem. This root apex is not very long (e.g., ≤1cm). The root apex consisting of the root apical meristem, juvenile cells derived from the apical meristem, and root cap distally Root hairs are unicellular, filament‐like protuberances from the surface of the root. More proximal then, is older root that is devoid of root hairs, contains lateral or secondary roots.  Older root may become woody in shrubs and trees. Diagram of a shoot apex  Examine the germinated maize seedling. Use a dissecting scope for close observations at the tip.  Draw the root and label the root hairs and the root cap.  What is the function of the root hairs? Do the root hairs extend to the very tip? Explain why they do or why they don’t. Can you discern the root cap? The primary root usually develops as a prominent taproot, which may give rise to lateral roots. This system, in which the primary root is dominant in size, is called a taproot system. When the primary root or any single root is not dominant and the system is more homogeneous in appearance. This is called a fibrous root system. Taproot system Fibrous system Describe each type of the given plants as either tap‐ or fibrous‐ in their root system morphology.  Basic Shoot Study The vegetative shoot consists of the two organs, stem and leaf.  Each leaf is attached to the stem at a node.  An axillary bud is formed in the axil of each leaf. The stretch of stem between two successive nodes is called an internode. All cells and organs of the primary plant body ultimately arise from the shoot apical meristem. The tip of a shoot that contains the apical meristem and leaf primordia and axillary bud primordia is called the shoot apex. Diagram of a shoot apex  Parts of a Typical Leaf Many leaves are differentiated into a blade (flattened, expanded portion) and petiole.  A petiolate leaf has a petiole, a sessile leaf lacks one. Stipules (a small pair of appendages) may also be present at the base of a leaf.  The leaf is stipulate when present, exstipulate when lacking. The leaves of many monocot angiosperms (e.g., grasses, lilies, orchids) lack a true petiole and have a sheathing leaf base. a‐f. Label the parts of the leaf below using any of the terms above.  Leaf Complexity  Leaves may either be simple (one blade) or compound (subdivided into more than one blade called leaflets). Compound leaves may be trifoliate (divided into 3 leaflets), pinnate (>3 leaflets arranged laterally along one central axis called a rachis), or palmate (>3 leaflets all radiating from a single point). Compound leaves may be once or twice pinnately compound , (e.g., 2‐pinnate, also called bipinnate). Compound leaves are typically petiolate, and the petiole is the leaf stalk between the stem and the first leaflet. After the petiole, the main leaf axis distal to the first leaflet of a pinnately compound leaf is called the rachis. A secondary or higher order rachis on a bipinnate or higher‐pinnate leaf is called a rachilla (plural rachillae). The stalk (if any) of a leaflet in a compound leaf is called a petiolule.  Leaf/Blade Margins Blade margins may be entire (no teeth or lobes), toothed, or lobed. Lobed margins may be pinnately lobed (lobes arranged laterally along an imaginary central axis), or palmately lobed (lobes radiating from more or less a single point).  Venation  The main or primary vascular bundles (i.e., plant “veins”) of leaves may be arranged in various patterns.  Pinnate venation has a central midvein with lateral secondary veins.  Palmate venation is where there are multiple main veins radiating from a single point at or near the blade base  Parallel venation is where the main veins run more or less parallel to each other.  The secondary or tertiary veins off of the primary veins of the pinnate and palmate types are generally referred to as “reticulate venation”. a‐c. Label the diagrams below appropriately.  Examine the leaves of the plant specimens provided and determine the phyllotaxy, stalking, stipule presence, complexity, margin, and venation of each. Record your observations of the leaf morphology below. Phyllotaxy Margin Complexity (alternate, (entire, (simple, Venation opposite, Stalking Stipules toothed, trifoliate, 1‐ (pinnate, Plant Name whorled, or (petiolate or (stipulate or pinnately pinnate, 2‐ palmate, basal or sessile) exstipulate) lobed, or pinnate, parallel) terminal palmately palmate) rosette) lobed)