Bio Lab Quiz 2

Why Plants?

Health and Medicine

Plants are crucial for the development of various medicines and treatments, with many pharmaceutical compounds originating from plant sources. For example, the pain reliever aspirin was derived from willow bark, and the cancer treatment taxol is sourced from the Pacific yew tree. Understanding plant properties and their bioactive compounds continues to play a significant role in drug discovery and therapeutic advancements.

Agriculture

Plants provide food and materials essential for sustenance and industry. Agriculture relies on cultivated plants, with staple crops such as rice, wheat, and maize providing the majority of global caloric intake. Additionally, plants play a crucial role in industrial applications, ranging from fiber for textiles to biofuels and bioplastics.

Genetics

Plant genetics studies contribute to advancements in biotechnology and crop improvement, enabling the development of genetically modified organisms (GMOs) that can resist pests, tolerate environmental stresses, and improve yield. Research in plant genomics aids in understanding the genetic inheritance of desirable traits, leading to more robust and sustainable agricultural practices.

Ecology/Environmental Science

Understanding plants is vital in studying ecosystems and environmental health, as they are primary producers that form the foundation of food chains. Plants contribute to carbon sequestration, habitat creation, and maintain soil health, playing an essential role in mitigating climate change and preserving biodiversity.

Evolutionary Models

Plants serve as models for understanding evolution and adaptation processes, offering insights into how species evolve to optimize their survival. Studies of phylogenetics and evolutionary biology involving plants help develop a clear picture of the historical relationships among various species and their adaptations to environmental challenges.

Plant Differentiation

Units of the Shoot

• Apical Meristem: The growing point of the shoot, crucial for lengthening and forming new leaves and buds.

• Node: The point on the stem where leaves or branches are attached, playing an essential role in plant growth and development.

• Axillary Bud: A potential shoot that can develop into a branch, contributing to the plant’s overall shape and spread.

• Internode: Segments of the stem located between nodes, which allow for vertical growth and provide structural support.

• Leaf: The photosynthetic organ of the plant that includes an area for gas exchange and energy production through photosynthesis.

Whole Plant Morphology

Eudicot

Eudicots are flowering plants characterized by features including:

• Terminal Bud: Located at the tip of the stem, responsible for vertical growth and leaf development.

• Axillary Bud: Holds the potential for lateral branching and plant expansion.

• Phytomer: The basic unit of plant structure, consisting of a node, internode, leaf, and bud, which plays a vital role in plant architecture.

Monocot

Monocots, or monocotyledons, are distinguished by their single seed leaf, parallel leaf veins, and fibrous root systems, making them significant in various ecosystems and agriculture (e.g., grasses, lilies, and orchids).

Tissue Types

Dermal Tissues - Exterior Surface

epidermis

• Waxy Cuticle: A protective layer that helps prevent water loss through evaporation.

• Trichomes: Hair-like structures that may serve various functions, including protection against herbivores and environmental stress.

• Stomata: Microscopic pores that facilitate gas exchange, mainly carbon dioxide intake and oxygen release.

Vascular Tissue - Transport

• Xylem: Transports water and dissolved minerals from the roots to the rest of the plant.

• Phloem: Responsible for the transport of sugars and organic molecules produced during photosynthesis to various parts of the plant.

Ground Tissue - Non-dermal/Vascular

• cortex

• Parenchyma: The most common type of cell with thin walls; involved in storage, photosynthesis, and tissue repair.

• Sclerenchyma: Thick-walled, supportive tissue that is often dead at maturity, providing structural strength to the plant.

Stem Cross Sections

Technique

For analysis, obtain sections from the tip and mid-region of the stem.

Equipment

Freehand sectioning may be less effective than using a microtome, which provides more precise and uniform slices for better observation.

Microtome Use

It is essential to match the microtome size to the sample type and stem diameter for optimal results.

Angiosperm Stem Cross-Sections

Key Components

• Phloem and Xylem: These vascular tissues form the transport systems for nutrients and water within the plant.

• Sclerenchyma: Provides structural support, reinforcing the plant’s strength.

• Epidermis: The outer layer protects the inner tissues and aids in water retention.

• Cortex: A type of ground tissue that often stores nutrients and aids in transportation.

Types of Steles

Different types of steles demonstrated through images:

• Protostele: A simple vascular structure found in primitive land plants.

• Radial Steles: Modified vascular structures improving nutrient and water transport efficiency.

• Siphonostele: More advanced vascular systems including ectophloic and amphiphloic types, allowing for greater versatility in transport.

• Dictyostele: A complex arrangement of vascular bundles commonly found in ferns, enhancing efficiency in transport and distribution.

Interpreting Your Stains

Tissue or Structure Staining Results

• Collenchyma: red- purple

• Parenchyma: red-purple, illustrating their functionality in metabolic processes.

• Sclerenchyma: blue-green, reflecting their structural purpose.

• Phloem: red.

• Xylem: green/blue-green,

• Starch Granules: Remain unstained, indicating their role in storage without disrupting cellular processes.

protected embryo (common ancestor)

stomata

green sporophyte

trachieds

microphyll & megaphyll

seeds

flowers

eudicots- ring vascular bundles

monocot- scattered vascular bundles

angio sperms- basal angiosperms, monocot, dicot

types of tissue-