Chapter 29: Plant Tissues

Chapter 29: Plant Tissues

Shoots and Roots Shoots (Leaves and Stem) Produce food by photosynthesis Carry out reproductive functions Roots Anchor the plant Penetrate the soil and absorb water and dissolved minerals

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

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

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

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

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

Inside seeds, two cotyledons seed leaves of embryo Inside seeds, one cotyledon seed leaf of embryo Usually four or five floral parts (or multiples of four or five) Usually three floral parts (or multiples of threes) Leaf veins usually in a netlike array Three pores or furrows in the pollen grain surface Leaf veins usually running parallel with one another One pre or furrow in the pollen grain surface Vascular bundles organized as a ring in ground tissue Vascular bundles distributed throughout ground tissue Fig. 29-4, p.495

Parenchyma: A Simple Tissue 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

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

Collenchyma: A Simple Tissue Specialized for support for primary tissues Makes stems strong but pliable Cells are elongated Walls thickened with pectin Alive at maturity

Collenchyma: A Simple Tissue Supports mature plant parts Protects many seeds Thick, lignified walls Dead at maturity Two types: Fibers: Long, tapered cells Sclereids: Stubbier cells

collenchyma parenchyma lignified secondary wall Fig. 29-7, p.496

Complex Tissues Composed of a mix of cell types Xylem Phloem Epidermis

Xylem Conducts water and dissolved minerals up the shoot Conducting cells are dead and hollow at maturity tracheids vessel member

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

Phloem: A Complex Vascular Tissue Transports sugars down the shoot Main conducting cells are sieve-tube members Companion cells assist in the loading of sugars sieve-tube member companion cell sieve plate

Epidermis: A Complex Plant Tissue Covers and protects plant surfaces Secretes a waxy, waterproof cuticle In plants with secondary growth, periderm replaces epidermis

leaf surface cuticle epidermal cell photosynthetic cell Fig. 29-9, p.497

Meristems 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

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

Fig. 29-10a1, p.498

immature leaf shoot apical meristem lateral bud forming cortex vascular tissues pith Fig. 29-10a2, p.498

immature leaf shoot apical meristem descendant meristems (orange) Fig. 29-10b, p.498

Lateral Meristems Increase girth of older roots and stems Cylindrical arrays of cells cork cambium vascular cambium thickening Figure 29.20.a Page 504

immature leaf shoot apical meristem descendant meristems (orange) cortex primary phloem primary xylem pith Stepped Art Fig. 29-10b-d, p.498

Internal Structure of a Dicot Stem 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

Internal Structure of a Monocot Stem The vascular bundles are distributed throughout the ground tissue No division of ground tissue into cortex and pith Figure 29.11.b Page 499

vessel in xylem meristem cell epidermis cortex vascular bundle pith sieve tube in phloem companion cell in phloem Fig. 29-11a, p.499

Common Leaf Forms DICOT petiole axillary bud MONOCOT blade blade node sheath node Figure 29.12.a,b Page 500

Adapted for Photosynthesis 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. 29-12c,d, p.500

Leaf Structure cuticle UPPER EPIDERMIS xylem phloem PALISADE MESOPHYLL SPONGY MESOPHYLL LOWER EPIDERMIS O 2 CO 2 one stoma Figure 29.14.b Page 501

leaf blade leaf vein Leaf Vein (one vascular bundle) cuticle Upper Epidermis Palisade Mesophyll stem xylem Water, dissolved mineral ions from roots and stems move into leaf vein (blue arrow) Spongy Mesophyll Lower Epidermis phloem 50 m Photosynthetic products (pink arrow) enter vein, will be transported throughout plant body Oxygen and water vapor diffuse out of leaf at stomata. Carbon dioxide in outside air enters leaf at stomata. cuticle-coated cell of lower epidermis one stoma (opening across epidermia) Fig. 29-14, p.501

Leaf Veins: Vascular Bundles Xylem and phloem; often strengthened with fibers In dicots, veins are netlike In monocots, they are parallel

Leaf Veins Fig. 29-15a, p.501

Leaf Veins Fig. 29-15b, p.501

Root Systems Taproot system of a California poppy Fibrous root system of a grass plant Figure 29.19 Page 503

Internal Structure of a Root 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

Root Structure 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 29.16.a Page 502

pith cortex epidermis VASCULAR CYLINDER primary xylem primary phloem Fig. 29-17, p.503

Fig. 29-18, p.503

Function of Endodermis 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

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

Fig. 29-19a, p.503

Fig. 29-19b, p.503

Secondary Growth 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

Fig. 29-20, p.504

VASCULAR CAMBIUM stem surface primary xylem primary phloem VASCULAR CAMBIUM secondary xylem secondary phloem Fig. 29-20b, p.504

Secondary Growth Ongoing cell divisions enlarge the inner core of secondary xylem and displace vascular cambium toward the stem Figure 29.20.c Page 504

Woody Roots primary xylem epidermis cortex procambium endodermis primary phloem pericycle Fig. 29-22a, p.505

epidermis cortex endodermis pericycle vascular cambium produced by pericycle vascular cambium produced by procambium vascular cambium pericycle derivatives vascular ray primary xylem primary phloem procambium secondary xylem secondary phloem cortex, epidermis slough off crushed primary phloem Stepped Art Fig. 29-22, p.505

A Coast Redwood Fig. 29-23, p.506

periderm (includes cork cambium, cork, new parenchyma) secondary phloem HEARTWOOD SAPWOOD BARK vascular cambium Fig. 29-24a, p.507

Annual Rings Concentric rings of secondary xylem Alternating bands of early and late wood Early wood Xylem cells with large diameter, thin walls Late wood Xylem cells with smaller diameter, thicker walls

Fig. 29-25a, p.507

Annual Rings Narrow annual rings mark severe drought years 1587 1589 1606 1612 Fig. 29-27c, p.509