Key Characteristics and Structures of Plants

Plant

Multicellular eukaryotes that possess chlorophyll and conduct photosynthesis.

Autotrophic

Organisms that produce their own food through photosynthesis.

Cell wall

Provides structural support and protection, made of cellulose.

Alternation of generations

A reproductive cycle that includes both diploid and haploid stages.

Plasma membrane

Regulates movement in and out of the cell.

Chloroplasts

Site of photosynthesis.

Vacuole

Stores water, ions, and waste; helps maintain cell turgidity.

Nucleus

Contains genetic material.

Mitochondria

Site of cellular respiration.

Angiosperm Root System

Includes primary roots, lateral roots, and specialized structures such as root hairs for absorption.

Angiosperm Shoot System

Includes stems, leaves, and flowers; responsible for photosynthesis and reproduction.

Storage roots

Modified roots such as carrots and sweet potatoes.

Prop roots

Modified roots such as those found in corn.

Rhizomes

Horizontal underground stems.

Tubers

Modified stems such as potatoes.

Stolons

Runners that are modified stems.

Tendrils

Modified leaves found in peas.

Spines

Modified leaves found in cacti.

Monocots

Plants with one seed leaf (cotyledon).

Eudicots

Plants with two seed leaves (cotyledons).

Parenchyma

Simple cells involved in photosynthesis and storage.

Collenchyma

Elongated cells with thickened walls, providing flexible support.

Sclerenchyma

Cells with thick, lignified walls, providing structural support.

Ground Tissue

Includes parenchyma, collenchyma, and sclerenchyma.

Dermal Tissue

Outer layer of the plant, includes epidermis and cuticle.

Vascular Tissue

Includes xylem (water transport) and phloem (food transport).

Blade

Main photosynthetic surface of a leaf.

Petiole

Stalk that attaches the leaf to the stem.

Veins

Vascular tissue in leaves, consisting of xylem and phloem.

Primary Growth in Shoot

Results in the formation of the epidermis, cortex, vascular bundles, and pith.

Primary Growth in Root

Results in the formation of epidermis, cortex, vascular cylinder, and root cap.

Indeterminate Growth

Growth that continues throughout life, such as at the tips of roots and shoots.

Meristems

Undifferentiated cells at the tips of roots and shoots that divide continuously.

Root caps

Protect the growing tip of roots and secrete mucilage to lubricate and reduce abrasion.

Downward Root Growth

Positive gravitropism and elongation of cells in the root apical meristem force roots downwards.

Xylem Cells

Tracheids and vessel elements (vessel elements are unique to angiosperms).

Phloem Cells

Sieve tube elements, companion cells.

Secondary Growth and Annual Rings

The vascular cambium produces xylem and phloem; xylem rings form annually.

Girdling

Removal of bark (and phloem) disrupts transport of sugars and kills the tree.

Water Potential

Factors Affecting Water Potential: Solute concentration, pressure, and temperature.

Water Potential Formula

Ψw=Ψs+Ψp

Ψw

Water potential

Ψs

Solute potential (osmotic pressure)

Ψp

Pressure potential

Water Movement

Water moves from regions of higher water potential to lower water potential.

Regulation of Transpiration

Stomata control water loss; guard cells open and close stomata in response to environmental factors.

K+ and Stomata

K+ influx causes stomatal opening (water follows by osmosis).

Symplastic Transport

Water moves through plasmodesmata between cells.

Apoplastic Transport

Water moves through the cell wall spaces, bypassing membranes.

Key Macronutrients

Nitrogen, phosphorus, potassium, sulfur, calcium, magnesium.

Role of Soil Bacteria

Nitrogen-fixing bacteria (e.g., Rhizobium) convert atmospheric nitrogen to ammonia; other bacteria convert ammonia to nitrate.

Carnivorous Plants

Adapted to nutrient-poor soils, they obtain nitrogen through capturing and digesting animals.

Mycorrhizae

Symbiotic relationship where fungi help plants with nutrient absorption, and fungi gain sugars from the plant.

Phototropism

Auxin hormone causes cells on the shaded side of the stem to elongate, causing the plant to bend toward light.

Gravitropism

Roots grow downward in response to gravity (positive gravitropism), stems grow upward (negative gravitropism).

Statoliths

Amyloplasts in the root cap help sense gravity.

Thigmotropism

Plants respond to touch; e.g., tendrils coiling around objects.

Auxin and Cytokinins

Auxin inhibits lateral bud growth (apical dominance), cytokinins promote lateral bud growth.

Gibberellins and Abscisic Acid (ABA)

Gibberellins promote seed germination, while ABA induces seed dormancy.

Indeterminate Growth

Growth that continues throughout the life of the plant.

Meristem

Region of undifferentiated cells where growth occurs.

Cork Cambium

Produces bark and cork cells.

Xylem

Tissue responsible for water transport.

Phloem

Tissue responsible for food transport (sugars).

Gravitropism

Response to gravity.

Thigmotropism

Response to touch.