Plant Biology Overview

Plant Needs

• Plants need sunlight for photosynthesis
• Carbon dioxide (CO2) is taken in through gas exchange
• Water is essential
• Protection from herbivores and diseases
• Ability to reproduce sexually or asexually
• Nutrients are necessary for growth

Root Functions

• Anchoring the plant in the soil
• Absorbing water and nutrients from the soil
• Storing carbohydrates (starch)

Root Types

• Taproots: Large, deep roots (e.g., carrots)
• Fibrous roots: Many thin, branching roots spreading near the surface (e.g., grasses)

Water Uptake by Roots

• Water moves from high concentration in the soil to low concentration in the roots (osmosis)
• Water travels up the xylem vessels due to capillary action, root pressure, and water molecule properties
• Water used to replace water lost during transpiration

Leaf Structure

• Petiole: Stalk connecting the blade to the stem
• Veins: Branching network throughout the leaf
• Blade: The broad, flat part of the leaf

Photosynthesis in Leaves

• Leaves are primary sites of photosynthesis
• Photosynthesis: CO2 + H2O + sunlight = glucose + O2
• Mesophyll cells contain chloroplasts

Leaf Benefits

• Source of medicines (e.g., digitalis, rosy periwinkle)

Leaf Drawbacks

• Some plants produce toxins (e.g., rhubarb)

Vascular Tissue

• 4 Types: Vascular, Epidermal, Ground

Xylem

• Dead cells that transport water and nutrients upward
• Capillary action helps water move up the xylem
• Transpiration helps pull water upward

Phloem

• Living cells that transport sugars (glucose)
• Can transport sugars up or down
• Sugar storage is critical for plant survival

Sugar Cycle

• Sugars are produced through photosynthesis
• Source cells have high sugar concentration
• Sink cells have low sugar concentration
• Excess sugar is converted to starch for storage

Seeds

• Protect and nourish plant embryos
• Assist in transporting the embryo to a new location

Sexual Reproduction (Angiosperms)

• Flowers contain male (stamens) and female (carpels) parts
• Pollen (from anther) fertilizes ovules in ovary
• Ovary develops into fruit
• Seeds develop from fertilized ovules

Tropisms

• Phototropism: Growth in response to light (e.g. plant growing toward light)
• Gravitropism: Growth in response to gravity (e.g. roots growing down)
• Thigmotropism: Growth in response to touch (e.g. vine wrapping around an object)

Essential Plant Chemicals (in summary)

• Auxins: Cell elongation (photosynthesis)
• Gibberellins: Cell elongation
• Cytokinins: Cell division
• ABA: Dormancy and stomata control
• Ethylene: Stress hormone

Explore the essential needs of plants, including sunlight, water, and nutrients. This quiz covers root functions and types, along with the structure of leaves and water uptake processes. Test your understanding of these fundamental plant biology concepts.