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Honors Biology

Chapter 9Plant Anatomy

John Regan

Wendy Vermillion

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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9.1 Plant organs

• Plant organs– Roots– Stems– Leaves– Flowers

• Roots1. Anchor plant to soil and give support

2. Absorb water and minerals

3. Increased surface area for absorption from root hairs• Epidermal extensions

4. Produce growth hormones

5. Food storage in perrenials-live year after year

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Organization of plant body

• Fig 9.1

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Vegetative organs of a tomato plant

• Fig 9.2

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Plant organs cont’d.

• Stems1. Provide structural support for leaves

2. Transport substances through plant body• Water and minerals from roots to leaves

• Products of photosynthesis from leaves to other organs for storage

3. Photosynthetic in some varieties

4. Store water in succulents– Node- point of attachment of leaf to stem– Internode- regions between nodes– Apical meristem- region of growth in length

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Plant organs cont’d.

• Leaves– Major synthetic organs in most varieties– Blade- wide portion of leaf– Petiole- stalk that attaches leaf to stem– Deciduous leaves- lost in cold weather

• Separates from stem at abscission layer

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Plant organs cont’d.

• Monocots versus eudicot plants– Eudicots are the larger group which includes many of the most

familiar flowering plants– Monocots include grasses, palms, and many important food

plants such as rice, wheat, and corn

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Flowering plants are either monocots or dicots

• Fig 9.3

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Plant tissues cont’d.

• Vascular tissue– Specialized for transport of substances through plant body– Two types of vascular tissue- xylem and phloem– Xylem- transports water and minerals– Phloem-transports food

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9.3 Organization of leaves

• Leaf Structure

– Cuticle – outer waxy covering, prevents water loss– Upper epidermis- protection– Mesophyll- cells have many chloroplasts

• Palisade mesophyll- elongated cells• Spongy mesophyll- irregular cells with many air spaces

which increase surface area for gas exchange

- Lower epidermis- protection, contains stomata(holes) surrounded by guard cells-regulate opening and closing of stomata

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Leaf structure

• Fig 9.8

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Classification of leaves

• Fig 9.9

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Shot tip and primary meristems

• Fig 9.11

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Organization of stems cont’d.

• Herbaceous stems-mature nonwoody stems– Exhibit only primary growth– Epidermis covered by waxy cuticle– Distinctive vascular bundles-xylem oriented to inside, phloem to

outside– Eudicots-vascular bundles in ring, central pith stores water and

carbohydrates, cortex wide and photosynthetic– Monocot-vascular bundles scattered, narrow cortex, large

amount of pith

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Herbaceous eudicot stem

• Fig 9.12

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Monocot stem

• Fig 9.13

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Organization of stems cont’d.

• Woody stems- have both primary and secondary tissues– Primary- formed from primary meristems behind shoot apical

meristem– Secondary-develop from lateral meristems: vascular cambium

and cork cambium– Primary growth is growth in length– Secondary growth increases girth and occurs only in conifers

and woody dicots

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Diagrams of secondary growth of stems

• Fig 9.14

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Tree trunk

• Fig 9.15

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Organization of stems cont’d.

• Stem diversity– Stolons- above ground horizontal stems, also called runners;

vegetative reproduction– Rhizomes- underground horizontal stems; vegetative

reproduction– Corms-bulbous underground stems

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Stem diversity

• Fig 9.16

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9.5 Organization of roots

• Root tip– Apical meristem protected by root cap– Root is divided into zones– Zone of primary cell division-primary meristems– Zone of elongation-cells lengthen as they differentiate– Zone of maturation- fully differentiated cells; root hairs present

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Eudicot root tip

• Fig 9.17

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Organization of roots cont’d.

• Tissues of an eudicot root– Epidermis-single layer of cells; root hairs present– Cortex-parenchymal cells containing starch granules– Endodermis-controls entrance of water and nutrients; boundary

between cortex and inner vascular cylinder– Vascular tissue-pericycle is the first layer of vascular

cylinder;can divide and give rise to lateral roots

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Organization of roots cont’d.

• Organization of monocot roots– Same growth zones as eudicot roots– Do not undergo secondary growth like many eudicot roots– Pith is surrounded by a vascular ring of alternating xylem and

phloem bundles

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Monocot root

• Fig 9.19

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Root diversity

• Fig 9.20

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Uptake and transport of nutrients cont’d.

• Stomata and water transport– Stomata must be open for water and mineral transport to occur– Each stoma is surrounded by a pair of guard cells– Guard cells regulate the opening and closing of the stomata– Blue light activates a flavin protein, which initiates activity of a H+

pump– K+ is actively transported into the guard cells

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Opening and closing of stomata

• Fig 9.23