Plant Structure, Growth, and Development (Ch. 35)

What are Angiosperms?

Angiosperm Body 2 Taxonomic classes monocots eudicots Monocots One cotyledon Parallel veins Floral parts in 3’s Fibrous Roots Eudicots Two cotyledons - Netlike veins -Floral parts in 4’s and 5’s Tap root

Angiosperm Body Need to be able to inhabit soil and air at the same time roots and shoots Plant morphology study of the external structure arrangement of flower parts, etc. Plant anatomy study of the internal structure arrangement of cells, tissues in a leaf, etc. Tissue – groups of cells, consisting of one or more types, that perform a specialized function Organ – consists of several types of tissues that together carry out specific functions

Angiosperm Body Two basic systems root system aerial shoot system (stems, leaves, flowers) Vascular Tissues transport materials xylem transports water and dissolved minerals phloem transports food

Root System Anchoring, absorbing water and minerals, storing carbohydrates Taproot system one large, vertical root mostly eudicots firm anchorage; one large vertical root stores lots of reserve food gives rise to lateral roots

Root System Fibrous root system mat of threadlike roots mostly monocots extensive exposure to soil, water, minerals concentrated in topsoil; prevents erosion

Root System Adventitious roots plant organ that grows in an unusual location arising above ground or from stems/leaves Root hairs thin, tubular extension of a root epidermal cells increase SA near root tip

Root System Mycorrhizae mutualistic relationship between fungi and roots Root nodules contain symbiotic bacteria to convert atmospheric nitrogen to compounds usable by the plant

Modified Roots (a) Prop roots (b) Storage roots (c) “Strangling” aerial roots (d) Buttress roots (e) Pneumatophores

Shoot System Vegetative shoots Stems and leaves Floral shoots Flowers Alternating system of nodes and internodes Raises or separates leaves Raise reproductive structures

Shoot System - Stems Nodes where leaves attach to stems Internodes segment of stem between nodes Axillary bud embryonic side shoot has potential to form a branch shoot usually dormant in young plants pruning

Shoot System - Stems Terminal (apical) bud bud on shoot tip; composed of developing leaves and a compact series of nodes and internodes where most of the growth of a young plant occurs May inhibit growth of axillary buds apical dominance

BELL RINGER

Modified Stems Stolons Runners allow plant to colonize a large area & reproduce asexually Rhizomes Horizontal stem that grows below ground Tubers Swollen ends of rhizomes; store food Bulbs Vertical, underground shoots

Modified Stems Rhizomes. The edible base of this ginger plant is an example of a rhizome, a horizontal stem that grows just below the surface or emerges and grows along the surface. (d) Tubers. Tubers, such as these red potatoes, are enlarged ends of rhizomes specialized for storing food. The “eyes” arranged in a spiral pattern around a potato are clusters of axillary buds that mark the nodes. (c) Bulbs. Bulbs are vertical, underground shoots consisting mostly of the enlarged bases of leaves that store food. You can see the many layers of modified leaves attached to the short stem by slicing an onion bulb lengthwise. (b) Stolons. Shown here on a strawberry plant, stolons are horizontal stems that grow along the surface. These “runners” enable a plant to reproduce asexually, as plantlets form at nodes along each runner. (a) Storage leaves Stem Root Node Rhizome

Shoot System - Leaves Main photosynthetic organ Blade Petiole (a) Simple leaf. A simple leaf is a single, undivided blade. Some simple leaves are deeply lobed, as in an oak leaf. (b) Compound leaf. In a compound leaf, the blade consists of multiple leaflets. Notice that a leaflet has no axillary bud at its base. (c) Doubly compound leaf. In a doubly compound leaf, each leaflet is divided into smaller leaflets. Axillary bud Leaflet Shoot System - Leaves Main photosynthetic organ Blade Joined to node by a petiole Venation (vascular tissue) parallel netted Classification shape spatial arrangement venation

Modified Leaves Tendrils on vines Spines of cacti Storage Reproductive Bracts

Dermal, Vascular, and Ground Tissues Tissue system A functional unit connecting all of the plant’s organs Dermal tissue system Outer protective covering Epidermis in nonwoody plants Cuticle Periderm in woody plants

Dermal, Vascular, and Ground Tissues Vascular tissue system Long distance transport b/w roots and stems Xylem and phloem Collectively called the stele Ground tissue system If internal to the vascular tissue  pith If external to the vascular tissue  cortex

Plant Cells Protoplast contents of a plant cell not including the cell wall Lignin Structural component of cell walls All start out similar to parenchyma cells; become more specialized Can generate an entire plant from one parenchyma cell

Plant Cells Parenchyma cells “typical” plant cell chloroplasts for photosynthesis large central vacuole store starch comprise fleshy tissue of fruits Collenchyma cells unevenly thick primary walls support for young plants without restraining growth living and flexible throughout life

Plant Cells Sclerenchyma cells rigid, thick secondary walls with lignin function only in support may be dead at maturity but produce secondary walls before protoplast dies Sclereids Very thick cell lignified cell walls; nutshells & seed coats Fibers Long, slender and tapered

Plant Cells Water-conducting cells of xylem dead at functional maturity allow water to flow from cell to cell tracheids In nearly all vascular plants Water moves through pits vessel elements Angiosperms and some gymnosperms Water moves through perforation plates

Plant Cells Food-conducting cells of phloem alive at functional maturity sieve-tube cells make the sieve tube elements/members that transport sucrose and other organic nutrients sieve plate Pores that allow flow from cell to cell companion cells Ribosomes and nucleus serve the sieve tube cell too

Figure 35.12 Locations of major meristems: an overview of plant growth

Meristems generate cells for primary and secondary growth Begins with germination and occurs throughout life of plant Indeterminate growth Meristems perpetually undifferentiated tissues Apical meristems Responsible for primary growth (growth in length) Lateral meristems Responsible for secondary growth (growth in thickness)

Meristems generate cells for primary and secondary growth Two types of lateral meristems Vascular cambium Add layers of vascular tissue called secondary xylem (wood) and secondary phloem Cork cambium Replaces the epidermis with thicker, tougher periderm

Plant Growth Finite life span genetically & environmentally determined annuals, biennials, and perennials Annuals Complete their life cycle in a year Cereal grains, legumes, wildflowers Perennials Live many years Trees, shrubs, some grasses Biennials Life span –generally 2 years Live through an intervening cold period between vegetative growth and flowering Beets, carrots

Figure 35.14 Primary growth of a root

Primary Growth Lengthens Roots and Shoots Primary growth of roots pushes roots through soil; root cap covers apical meristem Zone of cell division apical and primary meristems Zone of cell elongation elongate in size Zone of maturation specialize in function

Primary Growth Lengthens Roots and Shoots Epidermis Ground tissue Vascular tissue Stele Endodermis Pericycle

Primary Growth Lengthens Roots and Shoots Primary growth of shoots Apical meristems give rise to primary meristems Leaf primordia give rise to leaves Shoot elongation is due to lengthening of internode cells below the shoot tip Branching occurs due to activation of axillary buds

Tissue Organization of Stems Epidermis Covers stems Vascular tissue in bundles Axillary buds meristems develop lateral shoots Parenchyma, collenchyma, and scelerenchyma cells are present

Tissue Organization of Leaves Epidermis tightly locked cells protect from damage & pathogens waxy cuticle Stomata pores on underside of leaf site of gas exchange Guard cells control stomata opening for gas exchange Flaccid  stomata are closed due to lack of water

Tissue Organization of Leaves Mesophyll Ground tissue of leaf between epidermal layers palisade parenchyma upper half of leaf spongy parenchyma air spaces to allow O2 and CO2 to circulate lower half of leaf

Tissue Organization of Leaves

Vascular Cambium and Secondary Vascular Tissue Secondary growth of stems Stems and roots of woody plants vascular cambium transport and storage of starch Adds secondary xylem (wood) and secondary phloem cork cambium protective layers Bark (refers to all tissues external to vascular cambium) phloem, phelloderm, cork cambium, cork Secondary growth of roots

An overview of primary and secondary growth

Cork Cambium and Production of Periderm Phelloderm Thin layer of parenchyma cells that forms to the interior of the cork cambium Accumulation of cork cells Deposit suberin in walls then die Protects from water loss, physical damage, pathogens Lenticels Small, raised areas in the periderm Help cells to exchange gases

Growth, Morphogenesis, and Cell Differentiation Produce the Plant Body Development Specific series of changes by which cells form tissues, organs, and organisms Growth Irreversible change in size Cell division and expansion Morphogenesis Process that gives a tissue, organ, or organism its shape and determines the positions of cell types Pattern formation Differentiation Process by which cells with the same genes become different from one another Control of gene expression