The fanwort has two types of leaves -- developmental plasticity Figure 35.1 Why does this plant have two types of leaves?

Flowering Plant Morphology Reproductive shoot (flower) Apical bud Node Internode Apical bud Shoot system Vegetative shoot Blade Leaf Petiole Axillary bud Stem Figure 35.2 An overview of a flowering plant Taproot Lateral branch roots Root system

Root Hairs of a radish seedling Figure 35.3 Root hairs of a radish seedling

Prop roots “Strangling” aerial roots Storage roots Buttress roots Many plants have modified roots Prop roots “Strangling” aerial roots Storage roots Buttress roots Figure 35.4 Modified roots Pneumatophores

Prop roots - support tall top heavy plants Modified roots Figure 35.4 Modified roots Prop roots - support tall top heavy plants

Pneumatophores - “air roots” enable root systems to capture oxygen Modified Roots Figure 35.4 Modified roots Pneumatophores - “air roots” enable root systems to capture oxygen

Modified Roots Figure 35.4 Modified roots Buttress roots - support tall trunks of some tropical trees “like butresses.”

Many Plants have Modified Stems Rhizomes Bulbs Storage leaves Stem Stolons Stolon Figure 35.5 Modified stems Tubers

Simple vs. Compound Leaves (a) Simple leaf Petiole Axillary bud Leaflet (b) Compound leaf Petiole Axillary bud Figure 35.6 Simple versus compound leaves (c) Doubly compound leaf Leaflet Petiole Axillary bud

Spines “prickly” Photosynthesis is Some plant species have evolved modified leaves that serve various functions Tendrils cling Spines “prickly” Photosynthesis is carried out mainly by the fleshy stems Storage Leaves succulent plant leaves store water Reproductive leaves Little plantlets fall off and take root in the soil Figure 35.7 Modified leaves Bracts Look like petals Attract pollinators

Tendrils = Modified Leaves Figure 35.7 Modified leaves Tendrils -- cling --> thigmotropism

Ice Plant Leaves Store Water: Succulent Plants: Desert Adaptation Figure 35.7 Modified leaves Storage leaves

Tissue System: Each plant organ has:. dermal. vascular and Tissue System: Each plant organ has: * dermal * vascular and * ground tissues Figure 35.8 The three tissue systems Dermal tissue Ground tissue Vascular tissue

Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm Figure 35.10 Examples of differentiated plant cells Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm

Sclereid cells in pear (LM) Fig. 35-10c 5 µm Sclereid cells in pear (LM) 25 µm Cell wall Figure 35.10 Examples of differentiated plant cells Fiber cells (cross section from ash tree) (LM)

Vessel element Tracheids Differentiated Plant Cells in the Xylem - Dead at Maturity Vessel Tracheids 100 µm Pits Tracheids and vessels (colorized SEM) Figure 35.10 Examples of differentiated plant cells Perforation plate Vessel element Vessel elements, with perforated end walls Tracheids

Differentiated Plant Cells Sieve-tube elements: longitudinal view (LM) 3 µm Sieve plate Sieve-tube element (left) and companion cell: cross section (TEM) Companion cells Sieve-tube elements Plasmodesma Sieve plate Figure 35.10 Examples of differentiated plant cells 30 µm 10 µm Nucleus of companion cells Sieve-tube elements: longitudinal view Sieve plate with pores (SEM)

longitudinal view (LM) Sieve-tube elements: longitudinal view (LM) Sieve plate Companion cells Sieve-tube elements Figure 35.10 Examples of differentiated plant cells 30 µm

Sieve plate with pores (SEM) Sieve-tube element Plasmodesma Sieve plate 10 µm Nucleus of companion cells Figure 35.10 Examples of differentiated plant cells Sieve-tube elements: longitudinal view Sieve plate with pores (SEM)

An overview of primary and secondary growth Primary growth in stems Epidermis Cortex Shoot tip (shoot apical meristem and young leaves) Primary phloem Primary xylem Pith Lateral meristems: Vascular cambium Secondary growth in stems Cork cambium Axillary bud meristem Periderm Cork cambium Cortex Figure 35.11 An overview of primary and secondary growth Pith Primary phloem Primary xylem Root apical meristems Secondary phloem Secondary xylem Vascular cambium

Primary growth of a root Cortex Vascular cylinder Epidermis Key to labels Zone of differentiation Root hair Dermal Ground Vascular Zone of elongation Figure 35.13 Primary growth of a root Apical meristem Zone of cell division Root cap 100 µm

Organization of primary tissues in young roots Epidermis Cortex Endodermis Vascular cylinder Pericycle Core of parenchyma cells Xylem 100 µm Phloem (a) Root with xylem and phloem in the center (typical of eudicots) 100 µm (b) Root with parenchyma in the center (typical of monocots) Endodermis Key to labels Figure 35.14 Organization of primary tissues in young roots Pericycle Dermal Ground Vascular Xylem Phloem Organization of primary tissues in young roots 50 µm

Lateral roots arise from within the pericycle, the outermost cell layer in the vascular cylinder Epidermis Emerging lateral root Lateral root Cortex Figure 35.15 The formation of a lateral root 1 Vascular cylinder 2 3

Shoot tip Shoot apical meristem Leaf primordia Young leaf Developing vascular strand Figure 35.16 The shoot tip Axillary bud meristems 0.25 mm

Leaf anatomy Figure 35.18 Leaf anatomy Guard cells Key to labels Stomatal pore 50 µm Dermal Epidermal cell Ground Cuticle Sclerenchyma fibers Vascular Stoma (b) Surface view of a spiderwort (Tradescantia) leaf (LM) Upper epidermis Palisade mesophyll Bundle- sheath cell Spongy mesophyll Figure 35.18 Leaf anatomy Lower epidermis 100 µm Cuticle Xylem Phloem Vein Guard cells Vein Air spaces Guard cells (a) Cutaway drawing of leaf tissues (c) Cross section of a lilac (Syringa)) leaf (LM)

Secondary growth produced by the vascular cambium X X C P P Secondary phloem Secondary xylem X X C P X C P C C C C C X C C Figure 35.20 Secondary growth produced by the vascular cambium After one year of growth After two years of growth C C C

Anatomy of a tree trunk Growth ring Vascular ray Heartwood Secondary xylem Sapwood Fig 35.22 Anatomy of a tree trunk Vascular cambium Secondary phloem Bark Layers of periderm

Is this tree living or dead? Figure 35.23 Is this tree living or dead?

The plane and symmetry of cell division influence development of form Plane of cell division (a) Planes of cell division Figure 35.25 The plane and symmetry of cell division influence development of form Developing guard cells Unspecialized epidermal cell Guard cell “mother cell” (b) Asymmetrical cell division

The plane and symmetry of cell division influence development of form Cellulose microfibrils Figure 35.27 The orientation of plant cell expansion 5 µm Nucleus Vacuoles

Morphogenesis in plants, as in other multicellular organisms, is often controlled by homeotic genes Figure 35.30 Overexpression of a homeotic gene in leaf formation

Phase change in the shoot system Leaves produced by adult phase of apical meristem Figure 35.32 Phase change in the shoot system of Acacia koa Leaves produced by juvenile phase of apical meristem

Organ identity genes and pattern formation in flower development Pe Ca St Se Pe Se (a) Normal Arabidopsis flower Pe Pe Organ identity genes and pattern formation in flower development Figure 35.33 Organ identity genes and pattern formation in flower development Se (b) Abnormal Arabidopsis flower

The ABC hypothesis for the functioning of organ identity genes in flower development Sepals Petals Stamens A Carpels (a) A schematic diagram of the ABC hypothesis B C C gene activity B + C gene activity Carpel A + B gene activity Petal A gene activity Stamen Sepal Active genes: B B B B B B B B A A A A A A C C C C A A C C C C C C C C A A C C C C A A A B B A A B B A Figure 35.34 The ABC hypothesis for the functioning of organ identity genes in flower development Whorls: Carpel Stamen Petal Sepal Wild type Mutant lacking A Mutant lacking B Mutant lacking C (b) Side view of flowers with organ identity mutations

Growth regions Shoot tip (shoot apical meristem and young leaves) Vascular cambium Lateral meristems Cork cambium Axillary bud meristem Root apical meristems

You should now be able to: Compare the following structures or cells: Fibrous roots, taproots, root hairs, adventitious roots Dermal, vascular, and ground tissues Monocot leaves and eudicot leaves Parenchyma, collenchyma, sclerenchyma, water-conducting cells of the xylem, and sugar-conducting cells of the phloem Sieve-tube element and companion cell.

Explain the phenomenon of apical dominance. Distinguish between determinate and indeterminate growth. Describe in detail the primary and secondary growth of the tissues of roots and shoots. Describe the composition of wood and bark.

Distinguish between morphogenesis, differentiation, and growth. Explain how a vegetative shoot tip changes into a floral meristem.