I.Overview of plant systems II.Plant organs III.Plant tissues IV.Plant cells V.Plant growth A.Meristems B.Primary vs secondary C.Cell elongation & division VI. Before next class: review cell, tissue, and organ types and functions; see last slide for concept map assignment Lecture 9 Outline (Ch. 35)

Plant Structure, Growth, Development Plants are notably different from animals:

Setting the scene - animal bodies Cells  Tissues  Organs  Systems

Overview Recap - Plant Cells Plant cell structure recap Cell wall, plasmodesmata Primary wall (some have secondary wall), middle lamella

Overview – Monocots vs. Dicots Basic categories of plants based on structure and function

Plant “bodies” Three Basic Plant Organs: Roots, Stems, and Leaves Plants have organs composed of different tissues, which in turn are composed of cells Dermal tissue Ground tissue Vascular tissue ground Each plant organ has dermal, vascular, and ground tissue systems

Roots need sugars from photosynthesis; Shoots rely on water and minerals absorbed roots Plant Organs: Roots - Overview Root Roles: - Anchoring the plant - Absorbing minerals and water - Storing organic nutrients

Taproots: Fibrous roots: primary root forms and small branch roots grow from it (dicots) primary root dies, replaced by new roots from stem (monocots) Plant Organs: Roots - Comparisons

Prop roots “Strangling” aerial roots Storage roots Buttress roots Pneumatophores Roots – Many Plants Have Modified Roots Water storage

Stem: an organ made of –Alternating nodes, points of leaf attachment –Internodes, stem length between nodes Plant Organs: Stems - Overview Axillary bud – forms a lateral shoot/branch Apical (terminal) bud - near the shoot tip, lengthens a shoot Apical dominance maintains dormancy in most non-apical buds Apical bud Node Internode Apical bud Shoot system Vegetative shoot Axillary bud Stem

Rhizomes Bulbs Storage leaves Stem Stolons Stolon Tubers Stems – Many Plants Have Modified Stems

The leaf is the main photosynthetic organ of most vascular plants Plant Organs: Leaves - Overview Shoot system Leaf Blade Petiole Leaves generally have a flattened blade and a stalk called the petiole - joins the leaf to node of the stem

Leaves – Structure Leaves are several layers thick – different cell types Key to labels Dermal Ground Vascular Cuticle Xylem Phloem Sclerenchyma fibers Stoma Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis Cuticle Vein Guard cells

Plant Organs: Leaves Stomata flanked by two guard cells, control open vs. closed Leaf epidermis contains stomata - allow CO 2 exchange

Most dicots have branch-like veins and palmate leaf shape Monocots have parallel leaf veins and longer, slender blades Plant Organs: Leaves - Comparisons Monocots and dicots differ in the arrangement of veins, the vascular tissue of leaves

Tendrils Spines Storage leaves Reproductive leaves Bracts Leaves – Plants have modified leaves for various functions

1) Dermal Tissues Outer covering Protection 3) Ground Tissues “Body” of plant Photosynthesis; storage; support 2) Vascular Tissues “Vessels” throughout plant Transport materials Plant Tissue Systems

Dermal Tissue System (Covering of Plant): 1) Epidermal Tissue (epidermis): Outer layer Cuticle: Waxy covering - reduces evaporation/ predation Root Hairs: extended root surface - Increase absorption Plant Tissues - Dermis 2) Peridermal Tissue (periderm): Only in woody plants (“bark = dead cells”) Protection; support

Special Dermal Cells – Trichomes & Root hairs Trichomes –Hair-like projections –Keep leaf surfaces cool and reduce evaporation Roots hairs –Extend from epidermal cells –Greatly increase root’s surface area Plant Tissues - Dermis

Guard cells Stoma Epidermal cell Guard cells Stomata Epidermal cell Guard cells Stoma Epidermal cell Guard cells Stomata Epidermal cell 4 µm 200 µm 71 µm a.c. b. Paired sausage-shaped cells Flank a stoma (opening) Passage for oxygen, carbon dioxide, and water vapor Special Dermal Cells – Guard Cells Plant Tissues - Dermis

Vascular tissues made up of multiple cell types: Plant Tissues - Vascular Arranged in bundle(s) Xylem – water and nutrients Phloem – dissolved sugars and metabolites

1) Xylem (dead at maturity): water and minerals roots to shoots A)Tracheids: Narrow cells B)Vessel Elements: Wide cells C)Fibers: support Plant Tissues - Vascular

1) Xylem: Tracheids: - Most vascular plants - Thick walls, long and narrow - Water moves cell to cell through pits, less efficient Vessel elements: - Wider and shorter -Thinner walls -Perforation plates on ends -Water flows efficiently through plates Plant Tissues - Vascular

A)Sieve Tubes: Wide, tube-like cells B) Companion Cells: support and regulate sieve tubes 2) Phloem (living at maturity) cells: Plant Tissues - Vascular

- Moves water, sugar, amino acids & hormones 2) Phloem (living at maturity) Sieve tubes Long narrow, stack end to end Sieve plates at ends Lack most organelles: vacuole, cytoskeleton, nucleus, ribosomes Companion Cells Next to each sieve tube Don’t conduct water Regulate both cells (connected by numerous plasmodesmata) Plant Tissues - Vascular

Vasculature - Roots Epidermis Cortex Endodermis Vascular cylinder Pericycle Core of parenchyma cells Xylem Phloem Endodermis Pericycle Xylem Phloem Dermal Ground Vascular Key to labels 50  m 100  m (a) (b)Root with parenchyma in the center Root with xylem and phloem in the center Dicot Monocot

PhloemXylem Sclerenchyma (fiber cells) Ground tissue connecting pith to cortex Pith Cortex 1 mm Epidermis Vascular bundle Cross section of stem with vascular bundles forming a ring (typical of eudicots) (a) Key to labels Dermal Ground Vascular Cross section of stem with scattered vascular bundles (typical of monocots) (b) 1 mm Epidermis Vascular bundles Ground tissue In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring Vasculature - Stems DicotMonocot

Ground Tissue Plant Tissues – Ground Tissue Tissues that are not dermal nor vascular are ground tissue Internal to the vascular tissue is pith; external to the vascular tissue is cortex Cells specialized for storage, photosynthesis, and support –Includes parenchyma, collenchyma, sclerenchyma

We examined vasculature in roots and stems: Match each term number with a letter for the image: 1.Monocot stem 2.Monocot root 3.Dicot stem 4.Dicot root A.B. C.D.

Additional Plant Cell Types 1) Parenchyma (most abundant): plant metabolism: Photosynthesis; hormone secretion; sugar storage Flexible, thin-walled cells; living Parenchyma cells in Elodea leaf thin wall permeable to gasses large central vacuole able to divide and differentiate

2) Collenchyma: Thick-walled; living Support Able to elongate Grouped in strands Collenchyma cells in sunflower Additional Plant Cell Types

3) Sclerenchyma: Thick, hard-walled; Dead Offer support Thick secondary walls with lignin Sclereid cells in pear (LM) Fiber cells in ash tree Cell wall Additional Plant Cell Types Rigid (cannot elongate) Two types – sclereids and fibers

Think about plant “bodies” in comparison to animal bodies: A.For humans list: 2 CELL TYPES 2 TISSUES 2 ORGANS B. For plants list: 3 CELL TYPES 3 TISSUE SYSTEMS 3 ORGANS

Plant Growth: 1) Indeterminate: Grow throughout life 2) Growth at “tips” (length) and at “hips” (girth) Growth patterns in plant: 1) Meristem Cells: Dividing Cells 2) Differentiated Cells: Cells specialized in structure & role Form stable, permanent part of plant Plant Growth

1) Primary Growth: 1) Increased length 2) Specialized structures (e.g. fruits) 2) Secondary Growth: Responsible for increases in stem/root diameter Apical Meristems: Mitotic cells at “tips” of roots / stems Lateral Meristems: Mitotic cells “hips” of plant Plant Growth girth length

Shoot Growth – primary growth

Four regions: –Root cap Protection, gravity detection –Zone of cell division Mitotic divisions –Zone of elongation Cells lengthen, no division –Zone of maturation Cells differentiate, outer layer becomes dermis Root Growth – primary growth

Plant Growth in woody plants (secondary growth) Two lateral meristems: vascular cambium and cork cambium Pith Primary xylem Vascular cambium Primary phloem Cortex Epidermis thicker, stronger stems Vascular Cambium: between primary xylem and primary phloem

Stem – Secondary Growth: Plant Secondary Growth Produced inside stem: A) Secondary xylem - moves H 2 O, inward B) Secondary phloem - moves sugars, outward Pith Primary xylem Vascular cambium Primary phloem Cortex Epidermis Vascular ray Growth Secondary xylem Secondary phloem First cork cambium Cork

Plant Secondary Growth Vascular Cambium: Pith Primary xylem Vascular cambium Primary phloem Cortex Epidermis Vascular ray Growth Secondary xylem Secondary phloem First cork cambium Cork Growth Cork Bark Most recent cork cambium Layers of periderm

A hammock is hung between two trees in his backyard by a young man who is 15 years old. If he returns 20 years later to find his hammock, how will the position of the hammock have changed?

Plant Growth – cell growth Plant cells have cellulose microfibrils in the cell wall These can be enzymatically loosened, and the cell expanded by storing water in the central vacuole. Later the fibrils reattach.

Plant Growth – asymmetric divisions Often plant cells divide unequally in specifying cell types. For example, to form guard cells of stomata, the first division is toward one end of the cell. The second division is rotated 90 degrees. Two guard cells Unspecialized epidermal cell

At Home: Make a concept map to logically group and link vocabulary for plant organs, tissues, cells