Plant Tissues

 Volcano is located in southwestern Washington state  In 1980 it erupted, blowing 500 million metric tons of rock and ash outward  Ash and lava devastated about 40,500 acres of what had been forest

 Plants moved into the empty habitat almost immediately  Fireweed and blackberry were early colonists  In less than ten years, willow and alders were on the scene

 The angiosperms are seed-bearing vascular plants  In terms of distribution and diversity, they are the most successful plants on Earth  The structure and function of this plant group help explain its success

 Shoots  Produce food by photosynthesis  Carry out reproductive functions  Roots  Anchor the plant  Penetrate the soil and absorb water and dissolved minerals  Store food

Shoot Apical Meristem primary meristems active epidermis, ground tissues, primary vascular tissues forming primary meristems active Root Apical Meristem Fig. 29-3a, p.494

Protoderm Ground meristem Procambium epidermis ground tissues primary vascular tissues a The cellular descendants of apical meristems divide, grow, and differentiate. They form three primary meristems, the activity of which lengthens shoots and roots: Fig. 29-3a1, p.494

vascular cambium cork cambium Lateral Meristems thickening Fig. 29-3b, p.494

VASCULAR TISSUES GROUND TISSUES SHOOT SYSTEM ROOT SYSTEM EPIDERMIS  Ground tissue system  Vascular tissue system  Dermal tissue system Fig. 29-2, p.494

Parallel veins Netlike veins 3 pores 1 pore 4 or 5 floral parts 3 floral parts 1 cotyledon 2 cotyledons Vascular bundles dispersed Vascular bundles in ring

Made up of only one type of cell Parenchyma Collenchyma Sclerenchyma

 Most of a plant’s soft primary growth  Pliable, thin walled, many sided cells  Cells remain alive at maturity and retain capacity to divide  Mesophyll is a type that contains chloroplasts

stem epidermis simple and complex tissues inside the stem parenchyma vessel of xylem phloem fibers of sclerenchyma Fig. 29-6, p.496

 Specialized for support for primary tissues  Makes stems strong but pliable  Cells are elongated  Walls thickened with pectin  Alive at maturity

 Supports mature plant parts  Protects many seeds  Thick, lignified walls  Dead at maturity  Two types:  Fibers: Long, tapered cells  Sclereids: Stubbier cells

collenchymaparenchymalignified secondary wall Fig. 29-7, p.496

Composed of a mix of cell types Xylem Phloem Epidermis

 Conducts water and dissolved minerals  Conducting cells are dead and hollow at maturity vessel member tracheids

one cell’s wall pit in wall sieve plate of sieve tube cell companion cell ab c Fig. 29-8, p.497

 Transports sugars  Main conducting cells are sieve- tube members  Companion cells assist in the loading of sugars sieve plate sieve-tube member companion cell

 Covers and protects plant surfaces  Secretes a waxy, waterproof cuticle  In plants with secondary growth, periderm replaces epidermis

leaf surfacecuticleepidermal cell photosynthetic cell Fig. 29-9, p.497

 Regions where cell divisions produce plant growth  Apical meristems  Lengthen stems and roots  Responsible for primary growth  Lateral meristems  Increase width of stems  Responsible for secondary growth

activity at meristems new cells elongate and start to differentiate into primary tissues activity at meristems new cells elongate and start to differentiate into primary tissues Root apical meristem Shoot apical meristem

immature leaf shoot apical meristem lateral bud forming vascular tissues pith cortex Fig a2, p.498

immature leaf shoot apical meristem descendant meristems (orange) b Sketch of the shoot tip, corresponding to (a) Fig b, p.498

Protoderm Ground meristem Procambium Epidermis Ground tissue Primary vascular tissue

 Increase girth of older roots and stems  Cylindrical arrays of cells vascular cambium cork cambium thickening Figure a Page 504

immature leaf ground meristem primary phloem primary xylem pith procambium cortex procambium protoderm shoot apical meristem procambium epidermis Figure Page 498

immature leaf shoot apical meristem descendant meristems (orange) Stepped Art Fig b-d, p.498 primary phloem primary xylem pith cortex

Vascular cambium Cork cambium Secondary vascular tissue Periderm

 Outermost layer is epidermis  Cortex lies beneath epidermis  Ring of vascular bundles separates the cortex from the pith  The pith lies in the center of the stem Figure a Page 499

The vascular bundles are distributed throughout the ground tissue No division of ground tissue into cortex and pith Figure b Page 499

cortex epidermis vascular bundle pith vessel in xylem meristem cell sieve tube in phloem companion cell in phloem Fig a, p.499

epidermis vascular bundle pith vessel in xylem collenchyma sheath sieve tube in phloem companion cell in phloem air space Fig b, p.499

petiole blade axillary bud node blade sheath node DICOTMONOCOT Figure a,b Page 500

 Leaves are usually thin  High surface area-to-volume ratio  Promotes diffusion of carbon dioxide in, oxygen out  Leaves are arranged to capture sunlight  Are held perpendicular to rays of sun  Arranged so they don’t shade one another

POPLAR (Populus) OAK (Quercus) MAPLE (Acer) leaflet RED BUCKEYE (Aesculus) BLACK LOCUST (Robina) HONEY LOCUST (Gleditsia) Fig c,d, p.500

UPPER EPIDERMIS PALISADE MESOPHYLL SPONGY MESOPHYLL LOWER EPIDERMIS one stoma cuticle O2O2 CO 2 xylem phloem Figure b Page 501

leaf blade leaf vein stem Leaf Vein (one vascular bundle) cuticle Upper Epidermis Lower Epidermis Palisade Mesophyll Spongy Mesophyll 50  m xylem phloem cuticle-coated cell of lower epidermis one stoma (opening across epidermia) Oxygen and water vapor diffuse out of leaf at stomata. Carbon dioxide in outside air enters leaf at stomata. Water, dissolved mineral ions from roots and stems move into leaf vein (blue arrow) Photosynthetic products (pink arrow) enter vein, will be transported throughout plant body Fig , p.501

 A type of parenchyma tissue  Cells have chloroplasts  Two layers in dicots  Palisade mesophyll  Spongy mesophyll

 Xylem and phloem; often strengthened with fibers  In dicots, veins are netlike  In monocots, they are parallel

Fig a, p.501 Leaf Veins

Fig b, p.501 Leaf Veins

Taproot system of a California poppy Fibrous root system of a grass plant Figure Page 503

 Root cap covers tip  Apical meristem produces the cap  Cell divisions at the apical meristem cause the root to lengthen  Farther up, cells differentiate and mature Figure a Page 502

 Outermost layer is epidermis  Root cortex is beneath the epidermis  Endodermis, then pericycle surround the vascular cylinder  In some plants, there is a central pith

primary xylem primary phloem epidermis VASCULAR CYLINDER cortex pith Fig , p.503

 Ring of cells surrounds vascular cylinder  Cell walls are waterproof  Water can only enter vascular cylinder by moving through endodermal cells  Allows plant to control inward flow

 Both increase the surface area of a root system  Root hairs are tiny extensions of epidermal cells  Lateral roots arise from the pericycle and must push through the cortex and epidermis to reach the soil new lateral root

 Occurs in all gymnosperms, some monocots, and many dicots  A ring of vascular cambium produces secondary xylem and phloem  Wood is the accumulation of these secondary tissues, especially xylem

 Fusiform initials give rise to secondary xylem and phloem  Ray initials give rise to horizontal rays of parenchyma

Fig , p.504

Fig , p.505 Woody Roots

 All tissues outside vascular cambium  Periderm  Cork  New parenchyma  Cork cambium  Secondary phloem

periderm (includes cork cambium, cork, new parenchyma) secondary phloem BARK vascular cambium HEARTWOODSAPWOOD Fig a, p.507

1587– –1612 Fig c, p.509 Annual Rings  Narrow annual rings mark severe drought years