Structure and Function in Vascular Plants

Plant Structure and Function

• Natural selection has shaped the structure of vascular plants to enhance organ, tissue, and cellular function.
• Vascular plants exhibit a hierarchical organization: cells form tissues, which combine to create organs.

Vascular Plant Organs

• Three primary organs: roots, stems, and leaves facilitate resource acquisition from the environment.
• Roots draw water and minerals from the soil while stems and leaves access CO2 and light from above.

Roots

• Function includes anchoring the plant, absorbing water and minerals, and storing carbohydrates.
• Primary root develops first, with lateral roots branching off to enhance stability and absorption.

Stems

• Stems support leaves and buds, comprising nodes (attachment points for leaves) and internodes (segments between nodes).
• The apical bud at the shoot's tip promotes elongation, while axillary buds can develop into lateral branches.

Leaves

• Leaves are the primary site for photosynthesis, facilitating light interception, gas exchange, and heat dissipation.
• Structure typically includes a flattened blade and a petiole connecting to the stem.
• Leaf vein arrangements differentiate monocots (parallel veins) from eudicots (branching veins).

Tissue Types in Plants

• Plants consist of three main tissue types: dermal, vascular, and ground tissues, forming continuous systems throughout the plant.

Dermal Tissue

• Serves as protective outer layer; in nonwoody plants, this consists of a single epidermal layer, often covered in a waxy cuticle.
• In woody plants, periderm replaces epidermis in older structures.
• Specialized cells like guard cells facilitate gas exchange; trichomes help reduce water loss and deter pests.

Vascular Tissue

• Comprises xylem and phloem:
  • Xylem moves water and minerals upward from roots.
  • Phloem distributes sugars from leaves to growth and storage sites.

Ground Tissue

• Ground tissue includes pith (inside vascular tissue) and cortex (outside vascular tissue) for storage, photosynthesis, support, and transport functions.

Types of Plant Cells

• Plant cell differentiation results in specialized structure and function.
• Major cell types include:
  • Parenchyma: thin walls, large vacuoles, metabolic roles, and ability to divide.
  • Collenchyma: uneven primary wall thickness, providing flexible support to young shoots.
  • Sclerenchyma: rigid and supportive, containing lignin; many are dead at maturity.

Growth and Meristems

• Indeterminate growth enables continuous development throughout a plant's life.
• Meristems are undifferentiated tissues that allow for cell division, crucial for growth.
• Two types of meristems:
  • Apical: located at root and shoot tips, enabling primary growth and elongation.
  • Lateral: responsible for increasing thickness (secondary growth) in plants.