Plant Structure, Growth and Development
Types of Plants Nonvascular Vascular earliest plants, related to algae no special vascular tissues devoted to transport grow close to ground, near water use spores rather than seeds to reproduce mosses liverworts hornworts Vascular have true leaves, stems, roots vascular tissues: create “tubes” through plants
Plant Organization Plants have three levels of organization: Organs roots, stems, leaves Tissues dermal, vascular, ground Cell Types Xylem, phloem, parenchyma
Plant Structures Root System below ground multifunction Shoot System stem, branches, leaves, flowers and fruit vegetative shoots- stems and leaves floral shoots- bear flowers above ground
Roots Multicellular organs Anchors the plant Absorbs minerals and water Stores organic nutrients (sugars/starches) Root hairs: tiny extensions of epidermal cells Increase surface area for absorption Mycorrhizae: fungus + root symbiotic relationship
Root Anatomy
Root types Taproots One thick, vertical root Many lateral (branch) roots Firmly anchors Stores food Fibrous Mat of thin roots spread just below surface Shallow Increased surface area
Modified Roots
Stems Function: display leaves Consists of: nodes- where the leaves are attached internodes- stem segments between nodes - can be herbaceous (non-woody) or woody - used for support and conduction - two kinds of buds 1. axillary buds- found in the angle between the leaf and the stem 2. terminal buds- found at the end of the stem (where most growth occurs)
Modified Stems Runner or stolin Rhizome Bulb – underground shoot Aspen, strawberries, grass Grow on surface For asexual reproduction Rhizome Iris, ginger, potato, onion Grow underground Store food & DNA for new plant Tuber: end of rhizome Bulb – underground shoot Onion storage leaves
Leaves Function: photosynthetic organ Blades: flattened Petiole: stalk- joins leaf to node of a stem Most monocots have parallel veins Most eudicots have branching veins
Leaf Anatomy Layers Epidermis : two exterior surfaces (upper and lower) cuticle - waxy coat produced by epidermis protects against water loss and fungal or bacterial attack stomata- small openings on the underside of the leaf - transpiration (gas diffusion) guard cells swell or relax to close or open stomata, limit gas and water exchange Mesophyll: layer in between epidermis - rich in chloroplasts palisade layer - chloroplasts in columns just below the epidermal cells spongy layer - cells are less ordered , large intercellular spaces - facilitate the exchange of CO2 and O2
Modified Leaves
Plant Tissues Dermal (epidermis) - protects exterior of plant’s body - forms root hairs Vascular - phloem - xylem Ground (Parenchyma) - non dermal or vascular - pith - cortex
Plant Tissues- Dermal Single layer closely packed cells- cover entire plant Protect against water loss & invasion by pathogens Cuticle: waxy layer
Plant Tissues- Vascular Continuous throughout plant Transports materials between roots & shoots xylem – water,minerals roots shoots phloem- organic nutrients from leaves to where needed
Plant Tissues- Ground Tissue (Parenchyma) Anything that isn’t dermal or vascular Most common- make up the bulk of soft parts of plants Function: storage, photosynthesis, support Pith: inside vascular tissue Cortex: outside vascular tissue
Plant Growth Growth Patterns Indeterminate growth: plant can grow throughout its life Determinate growth: Plant ceases to grow at a certain size Plant Types: Annuals complete their life cycle in a year or less Perennials live for many years
Primary and Secondary Growth Growth Types Primary and Secondary Growth
dome of dividing cells at tip of terminal bud; divide and elongate Primary Growth (length) vertical growth of apical meristem in roots and shoots Roots Shoots dome of dividing cells at tip of terminal bud; divide and elongate
Secondary Growth (diameter) Occurs in lateral meristem in roots and shoots Vascular cambium: produces secondary xylem (wood) Cork cambium: produces tough covering that replaces epidermis Bark = all tissues outside vascular cambium