4.1 Systems in Plants: Comprehensive Study Guide on Flowering Plant Anatomy and Physiology
General Characteristics and Functional Principles of Plants
Plants are classified as multicellular organisms and include a diverse range of species such as mosses, ferns, conifers, and flowering plants.
Distinguishing Features: - Coloration: Plants are typically green due to the presence of chlorophyll, a chemical used for photosynthesis. - Motility: Plants are non-motile and cannot move from place to place. - Anchoring: All plants possess structures, usually roots, to anchor them firmly in a fixed location.
Structural Influence: These two primary features (photosynthesis and lack of movement) profoundly influence the overall structure and physical functioning of plants.
Biological Systems Comparison: Unlike animals, which are composed of many complex organ systems, a plant's body is divided into only two main “body systems.”
Rationale for Simplified Systems: Because plants perform photosynthesis to create their own food, they do not need to move to search for nutrition. Consequently, they do not require: - A digestive system. - A musculoskeletal system. - A nervous system for sensing surroundings and coordinating complex movements.
Essential Shared Functions: Despite their simplicity compared to animals, plants must still perform several shared biological functions: - Gas exchange with surroundings. - Internal transportation of water and nutrients. - Reproduction.
Traditional Medicines and Ethnobotany
Medicinal Statistics: Approximately of modern medicines are derived from plants.
Case Study - Dr. Memory Lewis: A Canadian researcher who conducts studies on medicines used by native peoples in South America. - Wound Healing: Her research has identified a specific tree sap that accelerates wound healing. - Malaria Treatment: Research into traditional medicines has uncovered plant compounds used to treat malaria, a disease affecting millions globally.
Conservation Concerns: Tropical jungles are currently being cleared for agricultural purposes, leading to the disappearance of plant species before they can be scientifically studied.
Hierarchy of Organization in the Flowering Plant Body
Terminology Differences: Scientists use different terminology to describe the hierarchy of organization in plants compared to animals.
Main Body Systems: - Root System: Typically grows below ground; anchors the plant, absorbs water and minerals, and stores food. - Shoot System: Specialized for photosynthesis and sexual reproduction; consists of the leaf, flower, and stem.
Nomenclature: While structures like roots, stems, leaves, and flowers are sometimes called "organs," scientists more frequently refer to them as "plant parts."
Specialized Tissues: Similar cells grouped together are called tissues. Plants feature three main tissue systems: - Dermal Tissue System: Tissues forming the outer surfaces of plant parts. - Vascular Tissue System: Tissues specialized for the transportation of water, minerals, and nutrients throughout the plant. - Ground Tissue System: Includes all other structures within a plant that are not dermal or vascular.
The Root System
Functions: - Anchors the plant in soil. - Absorbs water and minerals. - Stores food.
Absorption Mechanism: Most water and minerals are absorbed via root hairs, which are fine extensions of dermal tissue cells.
Variations and Adaptations: - Aerial Roots: In banyan trees, roots grow downward from branches to provide extra support and anchoring. - Oxygen Absorption: Some aquatic plants have specialized root extensions that grow upward out of the water to obtain oxygen for submerged root cells. - Nutrient Storage: Specific roots like radishes and carrots are specialized for storing high concentrations of nutrients.
Human Uses of Roots: - Food Sources: Sweet potatoes, carrots, sugar beets. - Flavorings: Liquorice, ginger. - Industrial/Craft Use: Fibers for basketry. - Medicine: Various natural remedies.
The Shoot System: The Leaf
Primary Function: The main photosynthetic structure.
Photosynthesis Process: Leaf tissues use carbon dioxide, water, and light energy to produce glucose (sugar) and oxygen.
Chemical Equation: .
Glucose Utilization: Used for plant growth, cellular respiration, and energy storage.
Intracellular Structure: - Chloroplast: The organelle responsible for photosynthesis. - Thylakoids: Flat, disc-like structures found inside chloroplasts. - Grana: Stacks of thylakoids that function as solar collectors using chlorophyll in their membranes. - Visual Detail: Light micrographs at magnification reveal chloroplasts as dark green structures with grana appearing light yellow.
Specialized Leaf Adaptations: - Support: Tendrils on cucumber plants are modified leaves. - Protection: Spines on a cactus are modified leaves designed to deter herbivores. - Attraction: The red leafy regions of poinsettias attract pollinators (the true flowers are the central yellow-green parts).
Human Uses of Leaves: - Food: Lettuce, spinach, onion, tea, herbs. - Industrial: Waxes and medicines. - Agriculture: Primary nutrition source for livestock.
The Shoot System: The Flower
Primary Function: Developed specifically for sexual reproduction.
Reproductive Structures: - Male: Produce pollen grains. - Female: Produce eggs.
Pollination and Development: After pollen fertilizes the eggs, female parts form seeds, which are often contained within a fruit.
Pollination Strategies: - Wind Pollination: Utilized by grasses and many trees. Flowers are small and drab but produce massive amounts of pollen. - Animal Pollination: Utilized by flowers attracting insects, bats, and birds. These flowers are typically large, colorful, fragrant, and produce nectar.
Human Importance: Flowers, seeds, and fruits provide rice, wheat, corn, vanilla, chocolate, coffee, bananas, apples, mangos, cotton, and medicines.
Non-Flowering Plants: Mosses, ferns, and conifers use different systems. Conifers are wind-pollinated and use specialized cones for pollen and seed production.
The Shoot System: The Stem
Primary Functions: - Supports branches, leaves, and flowers. - Provides physical transport routes for materials.
Internal Structure: Contains significant amounts of vascular tissue to move substances between the roots, leaves, flowers, and fruits.
Modified Functions: Stems can be specialized for food storage, protection, photosynthesis, and reproduction.
Human Uses of Stems: Sugar cane, potatoes (tubers), wood, paper products, cork, linen, and medicines.
Questions & Discussion
Evaluative Research Question: If a plant relies on wind pollination, but there is little wind when the pollen is ready to be spread, will grasses and trees fail to be pollinated that year?
Check Your Learning Discussion: - Q1: Hierarchy of structures? Plants are organized into body systems (root and shoot), which contain parts (leaves, stems, flowers, roots), which are composed of tissue systems (dermal, vascular, ground), which are made of specialized cells. - Q2: Differences from animals? Plants are green (chlorophyll) and immobile. Because they photosynthesize, they lack the need for complex organ systems like digestive or nervous systems. - Q3: Tissue types? Dermal (outer covering), Vascular (transportation), and Ground (internal support/structure). - Q4: Leaf vs. Stem? The leaf is for photosynthesis and reproduction attraction; the stem is for support and transport. - Q5: Stem vs. Root? The stem supports the aerial plant and transports materials; the root anchors the plant and absorbs soil nutrients. - Q6: Flower function? Primary function is sexual reproduction. Methods include wind pollination (drab/high pollen) and animal pollination (color/scent/nectar). - Q7: Food storage in parts? Roots (carrots), stems (potatoes), and leaves (onions) can all store food to sustain the plant during non-productive periods.