Plant Organ Systems and Functions

Plant Organ Systems and their Functions

• Plant systems are studied in terms of reproduction, development, nutrition, gas exchange, and transport.
• Homeostasis and feedback loops are examples of how organisms maintain stable internal conditions.
• Specialized structures and processes are responsible for homeostasis.

Plant Parts and Functions

• Roots: Absorb water and nutrients, anchor the plant, and store food.

• Two Types of Root Systems:

  • Fibrous root system – no primary dominant root
  • Tap root system – one primary root and many secondary roots

• Root Parts:

  • Primary root: The first root to emerge
  • Secondary roots: Roots that branch out from the primary root
  • Root hairs: Increase surface area for water absorption
  • Apical meristem: Area at the root tip for cell development
  • Root cap: Protects the apical meristem

• Stems: Support leaves, determine plant size/shape, transport water, minerals, and food, and some perform photosynthesis.

• Internal Stem Structure:

  • Xylem: Transports water and nutrients from roots to leaves, located near the stem's center
  • Phloem: Transports food produced in leaves to other parts of the plant, located near the stem's exterior
  • Cambium: Produces new xylem and phloem, positioned between xylem and phloem.

• Specialized Stems:

  • Bulbs: Short, flattened stems with fleshy leaves (e.g., onions)
  • Corms: Spherical structures similar to bulbs (e.g., gladiolus)
  • Rhizomes: Thick underground stems that lie horizontally (e.g., ginger)
  • Stolons: Horizontal stems that grow above ground (e.g., strawberry runners)
  • Tubers: Swollen rhizomes that store food (e.g., potatoes)

Leaves

• Leaves produce food for the plant by efficiently collecting light and converting it to energy.
• Leaf Parts:
  • Blade: Large, flat surface to collect sunlight
  • Petiole: Supports the leaf and connects it to the stem
  • Midrib: Main vein running down the center of the leaf
  • Veins: Transport water and food
  • Stipules: Small appendages at the base of the petiole
• Leaf Types:
  • Simple leaf: A single blade (e.g., cottonwood)
  • Palmately compound leaf: Multiple leaflets branching from a single point (e.g., white clover)
  • Pinnately compound leaf: Multiple leaflets branching along a central axis (e.g., black walnut)
  • Double compound leaf: Multiple leaflets branching from a secondary axis (e.g., honey locust)
• Vein Patterns:
  • Parallel veins: Parallel arrangement of veins
  • Netted or reticulate veins: Complex network of veins
• Leaf Layers:
  • Cuticle: Waxy layer to prevent water loss
  • Epidermis: Outer layer of protective cells
  • Palisade mesophyll: Layer of cells for photosynthesis
  • Spongy mesophyll: Layer of loosely packed cells for gas exchange
  • Stomata: Pores for gas exchange

Flowers

• Stamen: Male part of the flower, including the filament and anther, which produces pollen.
• Pistil: Female part of the flower, including the stigma, style, and ovary, which contains ovules.
• Parts of a Flower: Petals - Colorful part of the flower, Sepal - Protects the bud before opening, Stamen - Male part of the flower, Pistil - Female part of the flower.
• Types of Flowers:
  • Perfect flower: Has both male and female parts.
  • Imperfect flower: Missing either male or female parts.
• Sexual Reproduction in Plants: Pollination, movement of sperm to the ovule, fertilization occurs, ovary and surrounding part becomes fruit, fertilized eggs become seeds.

Plant Nutrition

• Essential Nutrients: Light, water, air, temperature are essential for plant nutrition.

Growth Regulators

• Plant hormones, also called phytohormones.
• Examples of plant hormones (growth regulators): auxins, cytokinins, ethylene, and abscisic acid.
• Functions of plant hormones: Germination, Growth to Maturities, Flowering, Fruit development, abscission (leaf fall), and seed dormancy;

Plant Classification

• Non-flowering Plants: Ferns, Conifers
• Flowering Plants: Monocots, Dicots
• Monocot and Dicot Categories/ Characteristics:
  • Number of Cotyledons, Leaf Venation, Root System, Flower Parts, Vascular Bundle Arrangement, Stem Growth, and Examples.