2. Plant Tissues and Primary Growth of Stems

Herb

A plant that does not become woody and often lives for less than a year.

Primary Plant Body

The non-woody structure of a plant, consisting of primary tissues.

Secondary Plant Body

The woody structure of a plant, including secondary tissues like wood and bark.

Parenchyma

Plant cells with thin primary walls; involved in metabolism and can be specialized (e.g., chlorenchyma, glandular cells).

Chlorenchyma

Parenchyma cells involved in photosynthesis, with numerous chloroplasts.

Glandular Cells

Parenchyma cells that secrete substances like nectar or oils.

Transfer Cells

Parenchyma cells with extensive plasma membrane ingrowths for short-distance transport.

Collenchyma

Cells with primary walls thickened at corners; provide support and flexibility.

Sclerenchyma

Cells with thick, lignified secondary walls; provide strength and support.

Fibers

Long, flexible sclerenchyma cells providing strength and elasticity.

Sclereids

Short, rigid sclerenchyma cells forming hard structures like seed shells.

Lignin

A complex polymer in sclerenchyma cells' secondary walls, providing strength and waterproofing.

Tracheary Elements

Conducting sclerenchyma in xylem, including tracheids and vessel elements.

Tracheids

Long, tapered xylem cells with secondary walls and bordered pits; conduct water.

Vessel Elements

Short, wide xylem cells with perforations for efficient water transport.

Sieve Cells

Long, narrow phloem cells with small sieve areas, associated with albuminous cells.

Sieve Tube Members

Short, wide phloem cells with large sieve plates, associated with companion cells.

Epidermis

Outermost layer of cells, including cuticle, guard cells, and trichomes.

Cuticle

A waxy layer on the epidermis preventing water loss and protecting against UV light.

Guard Cells

Cells surrounding stomata, regulating gas exchange.

Trichomes

Hair-like structures on plant surfaces, including simple, branched, and glandular types.

Perforations

Openings in vessel elements allowing rapid water flow.

Pits

Areas in tracheids and vessel elements for water movement between cells.

Geranium

Example of a herbaceous plant with roots, stems, and leaves; buds in the leaf axil.

Iris

Herbaceous plant with grass-like leaves, does not produce wood or bark.

Prickly Pear (Opuntia)

Plant with main shoot ("pad") and modified axillary branch shoots (spines); has two leaf types: fleshy leaves and spines.

Epiphytic Orchids

Plants that grow on trees, with photosynthetic roots exposed to sunlight.

Bromeliads

Plants that absorb water from fog condensing on their leaves; not rooted in sand.

Stolon

Elongated horizontal shoot with long, thin internodes; grows into new plants at suitable locations.

Corm

Vertical, thick stem with thin leaves; used for nutrient storage.

Bulb

Short shoot with thick, fleshy leaves; used for storage (e.g., onions, garlic).

Rhizome

Fleshy horizontal stem that spreads underground.

Tuber

Short horizontal stem for nutrient storage (e.g., potatoes).

Axillary Bud

Bud located in the leaf axil; can develop into a vegetative or floral shoot.

Phyllotaxy

Arrangement of leaves on a stem; includes alternate, opposite, whorled, distichous, decussate, and spiral types.

Celery

Food with collenchyma cells, causing stringiness.

Parenchymatous Foods

Foods made mostly of parenchyma cells; soft and easy to chew (e.g., apples, potatoes).

Sclereids in Pears

Cause grittiness in pears; seed coats and corn covering made of sclereids.

Sclerenchyma in Foods

Fibers and sclereids in foods like asparagus and beans; often not digestible.

Cutin

Fatty substance that makes the epidermal wall impermeable to water.

Aerenchyma

Cortex tissue with large intercellular air spaces, often found in aquatic plants.

Xylem

Vascular tissue that conducts water and minerals; includes tracheids and vessel elements.

Phloem

Vascular tissue that transports sugars and minerals; includes sieve cells and sieve tube members.

Companion Cells

Cells associated with sieve tube members that assist in loading sugars.

Vascular Bundles

Structures containing both xylem and phloem, located just inside the cortex.

Collateral

Arrangement of vascular bundles where xylem and phloem run parallel.

Primary Xylem

Xylem present in the primary plant body; includes tracheids and vessel elements.

Primary Phloem

Phloem present in the primary plant body; includes sieve elements and companion cells.

Roots

Plant organ that anchors the plant and absorbs water and nutrients from the soil.

Stems

Plant organ that supports leaves and transports fluids between roots and leaves.

Leaves

Plant organ primarily involved in photosynthesis.

Hornworts

Simple, non-vascular plants with small, green, ribbon-like bodies.

Liverworts

Simple, non-vascular plants, some with more complex structures and air chambers.

Mosses

Non-vascular plants with stems and leaves that may have simple or specialized water-conducting cells.

Indeterminate Growth

Continuous growth in plants due to cells at tips of shoots and roots that keep dividing.

Determinate Growth

Limited growth in animals and some plants where growth is fixed and organs are predetermined.

Annual Plants

Plants that complete their life cycle in one year with determinate growth.

Biennial Plants

Plants that live for two years, with leaf production in the first year and flowering in the second year.