Plant Morphology & Anatomy Plant Organs Types of Plant Organs  Vegetative organs:     Roots Leaves Stems Reproductive organs:   Flowers Fruits Plant Body Systems  The plant body is organized into a root system and a shoot system:   Root system is generally below ground Shoot system consists of vertical stems, leaves, flowers, & fruit s that contain seeds Root System “absorbtion” and “anchorage” … The Root System  Although we not see much of roots, they are equally important to plant growth as stems and leaves …  Leaves collect light and CO2 to produce sugar for growth as long as the plant can get enough water and nutrients from its roots! Types of Root Systems   A true root system consists of both primary & secondary roots (lateral roots) Primary root system:    Taproot System* Fibrous Root System** Adventitious Roots** *Found in most dicots **Found in most monocots Primary Root System   The 1st root to emerge from a seed is the radicle (primary root), which emerges to form a taproot that persists throughout the life of the plant Many progressively smaller branch roots (lateral roots) grow from the taproot  Taproot System Definition: the root system consisting of a thick, central primary root, which forms many smaller lateral roots    Common in dicots and conifers In some plants such as carrots and beets, fleshy taproots are the plant’s “food pantry” In other plants the long taproots are modified for reaching water deep in the ground   Fibrous Root System Definition: root system that consists of several to many roots of the same size that develop from the end of the stem with smaller, lateral roots branching off of them Typically slender, small roots   Found in monocots like onion, sweet potatoes, etc… Form in plants in which the embryonic root is short-lived Monocot vs Dicot Root External Root Structure    Branch roots Root hairs Root tip (root cap and apical meristem) Branch Roots   Also known as lateral roots or feeder roots when they are young Decrease in age from the soil surface to the root tip   Youngest roots occur closer to the root tip Soil texture influences root branching:  Plants that must grow through hard, dry soil have fewer branch roots than those in moist, loose soil Root hairs  Definition: short-lived, single-celled extensions of epidermal cells near the growing root tip    Form in the region of maturation Short, but numerous Function: raise absorptive capacity of the root by increasing surface area of the root that is in contact with moist soil Root cap   Definition: a protective thimble-like layer many cells thick that covers the delicate root apical meristem As the root grows and pushes its way through the soil, parenchyma cells of the root cap slough off and are replaced by new cells Root cap  The root cap consists of two types of cells:   Columella cells Peripheral cells Columella cells Peripheral cells Cortex Epidermis DIFFERENTIATION Vascular cylinder CELL DIVISION ELONGATION Root hair Cellulose fibers Apical meristem region Root cap Root apical Meristem    Regions of growth and development Located in the coneshaped root tip Divided into regions:  Region of division (grow & divide)  Zone of elongation (enlarge & specialize)  Zone of maturation (differentiation) Mucigel   A hydrated polysaccharide containing sugars, organic acids, vitamins, enzymes, and amino acids Functions:     Protection – from other plant’s roots Lubrication – lubricates roots as they move through the ground Water absorption – help maintain the connection between roots and water for a continuous flow Nutrient absorption – helps take in nutrients through intake of water Roots Have Cooperative Relationships with Others …  Roots often form mutualistic (beneficial) relationships with other organisms:  Mycorrhizae: mutualistic associations between plant roots and soil fungi;   Plants gain increased absorption of minerals and don’t need to produce as many root hairs; also fungi may protect against disease-causing fungi & worms (Fungus gets “food”.) Occurs in 80% of plants Roots Have Cooperative Relationships with Others …  Nitrogen-fixing Bacteria: Bacteria can convert nitrogen gas from the air into ammonium, which is incorporated into various organic molecules, which plants can take up   Only way for plants to get “useable” nitrogen Root nodules (see pictures to the right) are the “homes” of bacteria in the plants The End Columella cells • Elongate cells that contain 15-30 amyloplasts that sediment in response to gravity to the lower side of the cell – This is how plant roots perceive gravity Peripheral cells • Columella cells differentiate into peripheral cells within 23 days, which surround the columella cells – Thousands of these cells are shed from the cap as the plant pushes through the soil • Peripheral cells secrete large amounts of mucigel—a slimy substance with many Mucigel Peripheral cells ...Types of Plant Organs  Vegetative organs:     Roots Leaves Stems Reproductive organs:   Flowers Fruits Plant Body Systems  The plant body is organized into a root... lateral roots    Common in dicots and conifers In some plants such as carrots and beets, fleshy taproots are the plant? ??s “food pantry” In other plants the long taproots are modified for reaching... Strangling Roots  Help the plants to “climb” up another tree to get to sunlight; eventually will “strangle” the host plant (parasitic) Example: Fig Contractile Roots  Pull the plant shoot closer to