Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint TextEdit Art Slides for Biology, Seventh Edition Neil Campbell and Jane Reece Chapter 35 Plant Structure, Growth, and Development

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.1 Fanwort (Cabomba caroliniana)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.2 An overview of a flowering plant Reproductive shoot (flower) Terminal bud Node Internode Terminal bud Vegetative shoot Blade Petiole Stem Leaf Taproot Lateral roots Root system Shoot system Axillary bud

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.3 Root hairs and root tip

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.4 Modified roots (a) Prop roots(b) Storage roots (c) “Strangling” aerial roots (d) Buttress roots (e) Pneumatophores

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.5 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 Root

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.6 Simple versus compound leaves 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 Petiole Axillary bud Leaflet Petiole

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.7 Modified leaves (a) Tendrils. The tendrils by which this pea plant clings to a support are modified leaves. After it has “lassoed” a support, a tendril forms a coil that brings the plant closer to the support. Tendrils are typically modified leaves, but some tendrils are modified stems, as in grapevines. (b) Spines. The spines of cacti, such as this prickly pear, are actually leaves, and photosynthesis is carried out mainly by the fleshy green stems. (c) Storage leaves. Most succulents, such as this ice plant, have leaves modified for storing water. (d) Bracts. Red parts of the poinsettia are often mistaken for petals but are actually modified leaves called bracts that surround a group of flowers. Such brightly colored leaves attract pollinators. (e) Reproductive leaves. The leaves of some succulents, such as Kalanchoe daigremontiana, produce adventitious plantlets, which fall off the leaf and take root in the soil.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.8 The three tissue systems Dermal tissue Ground tissue Vascular tissue

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 35.9 Examples of Differentiated Plant Cells PARENCHYMA CELLS COLLENCHYMA CELLS SCLERENCHYMA CELLS SUGAR-CONDUCTING CELLS OF THE PHLOEM WATER-CONDUCTING CELLS OF THE XYLEM Parenchyma cells 60  m 80  m 5  m 25  m Cell wall Sclereid cells in pear Fiber cells Cortical parenchyma cells Collenchyma cells Vessel Tracheids 100  m Tracheids and vessels Vessel element Vessel elements with partially perforated end walls Pits Sieve-tube members: longitudinal view Companion cell Sieve-tube member Sieve plate Nucleus Cytoplasm Companion cell 30  m 15  m Tracheids

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure An overview of primary and secondary growth In woody plants, there are lateral meristems that add secondary growth, increasing the girth of roots and stems. Apical meristems add primary growth, or growth in length. Vascular cambium Cork cambium Lateral meristems Root apical meristems Primary growth in stems Epidermis Cortex Primary phloem Primary xylem Pith Secondary growth in stems Periderm Cork cambium Cortex Primary phloem Secondary phloem Vascular cambium Secondary xylem Primary xylem Pith Shoot apical meristems (in buds) The Cork cambium adds secondary dermal tissue. The vascular cambium adds secondary xylem and phloem.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Three years’ past growth evident in a winter twig This year’s growth (one year old) Last year’s growth (two years old) Growth of two years ago (three years old) One-year-old side branch formed from axillary bud near shoot apex Scars left by terminal bud scales of previous winters Leaf scar Stem Leaf scar Bud scale Axillary buds Internode Node Terminal bud

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Primary growth of a root Dermal Ground Vascular Key Cortex Vascular cylinder Epidermis Root hair Zone of maturation Zone of elongation Zone of cell division Apical meristem Root cap 100  m

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Time Lapse Root

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Organization of primary tissues in young roots Cortex Vascular cylinder Endodermis Pericycle Core of Parenchyma cells Xylem 50  m Endodermis Pericycle Xylem Phloem Key 100  m Vascular Ground Dermal Phloem Transverse section of a root with parenchyma in the center. The stele of many monocot roots is a vascular cylinder with a core of parenchyma surrounded by a ring of alternating xylem and phloem. (b) Transverse section of a typical root. In the roots of typical gymnosperms and eudicots, as well as some monocots, the stele is a vascular cylinder consisting of a lobed core of xylem with phloem between the lobes. (a) 100  m Epidermis

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The formation of a lateral root Cortex Vascular cylinder Epidermis Lateral root 100  m Emerging lateral root

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The terminal bud and primary growth of a shoot Apical meristemLeaf primordia Developing vascular strand Axillary bud meristems 0.25 mm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Organization of primary tissues in young stems Epidermis Vascular bundle Cortex Pith Ground tissue connecting pith to cortex Xylem Phloem Sclerenchyma (fiber cells) Ground tissue Epidermis Vascular bundles Key Dermal Ground Vascular 1 mm (a) A eudicot stem. A eudicot stem (sunflower), with vascular bundles forming a ring. Ground tissue toward the inside is called pith, and ground tissue toward the outside is called cortex. (LM of transverse section) (b) A monocot stem. A monocot stem (maize) with vascular bundles scattered throughout the ground tissue. In such an arrangement, ground tissue is not partitioned into pith and cortex. (LM of transverse section)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Leaf anatomy Key to labels Dermal Ground Vascular Guard cells Stomatal pore Epidermal cell 50 µm Surface view of a spiderwort (Tradescantia) leaf (LM) (b) Cuticle Sclerenchyma fibers Stoma Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis Cuticle Vein Guard cells Xylem Phloem Guard cells Bundle- sheath cell Cutaway drawing of leaf tissues(a) VeinAir spacesGuard cells 100 µm Transverse section of a lilac (Syringa) leaf (LM) (c)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Primary and secondary growth of a stem (layer 1) (a) Primary and secondary growth in a two-year-old stem Pith Primary xylem Vascular cambium Primary phloem Epidermis Cortex 1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Primary and secondary growth of a stem (layer 2) Vascular cambium 4 First cork cambium Pith Primary xylem Vascular cambium Primary phloem Epidermis Cortex 2 1 Growth Primary xylem Secondary xylem Primary phloem Cork Phloem ray 3 Xylem ray Secondary phloem (a) Primary and secondary growth in a two-year-old stem

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Primary and secondary growth of a stem (layer 3) Vascular cambium Pith Primary xylem Secondary xylem Vascular cambium Secondary phloem Primary phloem Periderm (mainly cork cambia and cork) Pith Primary xylem Vascular cambium Primary phloem Cortex Epidermis Vascular cambium 4 First cork cambium Secondary xylem (two years of production) Pith Primary xylem Vascular cambium Primary xylem Epidermis Cortex Growth Primary xylem Secondary xylem Secondary phloem Primary phloem Cork Phloem ray 3 Xylem ray Growth 9 Bark 8 Layers of periderm 7 Cork 5 Most recent cork cambium (a) Primary and secondary growth in a two-year-old stem Secondary phloem

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Secondary phloem Vascular cambium Late wood Early wood Secondary xylem Cork cambium Cork Periderm (b) Transverse section of a three-year- old stem (LM) Xylem ray Bark 0.5 mm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Cell division in the vascular cambium Vascular cambium C X C P C X C X C P P P C X X P C X X C C Types of cell division. An initial can divide transversely to form two cambial initials (C) or radially to form an initial and either a xylem (X) or phloem (P) cell. (a) Accumulation of secondary growth. Although shown here as alternately adding xylem and phloem, a cambial initial usually produces much more xylem. (b)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Anatomy of a tree trunk Growth ring Vascular ray Heartwood Sapwood Vascular cambium Secondary phloem Layers of periderm Secondary xylem Bark

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Arabidopsis thaliana Cell organization and biogenesis (1.7%) DNA metabolism (1.8%) Carbohydrate metabolism (2.4%) Signal transduction (2.6%) Protein biosynthesis (2.7%) Electron transport (3%) Protein modification (3.7%) Protein metabolism (5.7%) Transcription (6.1%) Other metabolism (6.6%) Transport (8.5%) Other biological processes (18.6%) Unknown (36.6%)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The plane and symmetry of cell division influence development of form Division in same plane Single file of cells forms Plane of cell division Division in three planes Cell divisions in the same plane produce a single file of cells, whereas cell divisions in three planes give rise to a cube. (a) Cube forms Nucleus Asymmetrical cell division Developing guard cells Unspecialized epidermal cell Unspecialized epidermal cell Guard cell “mother cell” Unspecialized epidermal cell An asymmetrical cell division precedes the development of epidermal guard cells, the cells that border stomata (see Figure 35.17). (b)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The preprophase band and the plane of cell division Preprophase bands of microtubules Nuclei Cell plates 10 µm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The orientation of plant cell expansion Cellulose microfibrils Vacuoles Nucleus 5 µm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The fass mutant of Arabidopsis confirms the importance of cytoplasmic microtubules to plant growth Wild-type seedling fass seedling Mature fass mutant (a) (b) (c)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Establishment of axial polarity

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Overexpression of a homeotic gene in leaf formation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Control of root hair differentiation by a homeotic gene When epidermal cells border a single cortical cell, the homeotic gene GLABRA-2 is selectively expressed, and these cells will remain hairless. (The blue color in this light micrograph indi- cates cells in which GLABRA-2 is expressed.) Here an epidermal cell borders two cortical cells. GLABRA-2 is not expressed, and the cell will develop a root hair. The ring of cells external to the epi- dermal layer is composed of root cap cells that will be sloughed off as the root hairs start to differentiate. Cortical cells 20 µm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Phase change in the shoot system of Acacia koa Leaves produced by adult phase of apical meristem Leaves produced by juvenile phase of apical meristem

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure Organ identity genes and pattern formation in flower development Normal Arabidopsis flower. Arabidopsis normally has four whorls of flower parts: sepals (Se), petals (Pe), stamens (St), and carpels (Ca). Abnormal Arabidopsis flower. Reseachers have identified several mutations of organ identity genes that cause abnormal flowers to develop. This flower has an extra set of petals in place of stamens and an internal flower where normal plants have carpels. (a) (b) Ca St Pe Se Pe Se Pe Se

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure The ABC hypothesis for the functioning of organ identity genes in flower development Sepals Petals Stamens Carpels C gene activity B + C gene activity A + B gene activity A gene activity (a) A schematic diagram of the ABC hypothesis. Studies of plant mutations reveal that three classes of organ identity genes are responsible for the spatial pattern of floral parts. These genes are designated A, B, and C in this schematic diagram of a floral meristem in transverse view. These genes regulate expression of other genes responsible for development of sepals, petals, stamens, and carpels. Sepals develop from the meristematic region where only A genes are active. Petals develop where both A and B genes are expressed. Stamens arise where B and C genes are active. Carpels arise where only C genes are expressed. Active genes: Whorls: Stamen Carpel Petal Sepal Wild type Mutant lacking AMutant lacking BMutant lacking C (b) Side view of organ identity mutant flowers. Combining the model shown in part (a) with the rule that if A gene or C gene activity is missing, the other activity spreads through all four whorls, we can explain the phenotypes of mutants lacking a functional A, B, or C organ identity gene. A A C C C C A A CCCCCCCC A A C C C C A A A B B A A B B A B B B B BB B B A A A A A B C