introduction to plants kingdom: plantae plants: cell wall autotroph (photosynthesis) ...
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Introduction to PlantsKingdom: Plantae
Plants: Cell wall Autotroph (photosynthesis) Multi-cellular
12 Divisions (Phyla) Anthophyta = Angiosperms (flowering plants)
Largest # of species (~250,000 - 90% plants) Seed plants: product seed w/in a fruit Key adaptations: flowers & fruits Sporophytes are trees, shrubs, herbs that flower 2 main groups: Monocots & Dicots
Monocots vs. Dicots
Monocot Dicot
• One cotyledon (seed leaf) •Two cotyledon
• Parallel veins in leaves •Netted veins in leaves
• Fibrous root system •Taproot
• Floral parts in multiples of 3 •Floral parts in multiple layers of 4 or 5
• Complex vascular arrangement •Ring vascular arrangement
• Eg. grass, corn, palm, onion, tulip, bamboo •Eg. bean, pea, rose, sunflower
Concept 35.1 The plant body has a heirarchy of organs, tissues, and cells
Basic Organs
• Roots• Stems• Leaves
Types of Tissue
• Dermal• Vascular• Ground
Cell Types
• Parenchyma• Collenchyma• Sclerenchyma• Xylem• Phloem
•Above ground•Stems, leaves
•Underground (usually)•Roots
Shootsystem
Rootsystem
A. Roots Anchors plant, absorbs H2O & minerals, stores
sugars/starches Root hairs – tiny extensions of epidermal cells,
increase surface area for H2O and mineral absorption
Mycorrhizae: symbiosis with fungi
Root hairs
Fibrous Roots Taproots•Mat of thin roots spread just below surface •One thick, vertical root
•Shallow •Many lateral (branch) roots
• Increased surface area •Firmly anchors
•Monocots •Stores food in root
•Dicots
Fibrous Root(scallion)
Taproot(carrot)
Roots
B. Stems Alternating system of nodes (leaf
attachment) and internodes Function: display leaves
Terminal bud – growth concentrated at apex (tip)
Apical dominance: terminal bud prevents growth of axillary buds; growth directed upward, toward light
Axillary buds – located in V between leaf and stem; forms branches (lateral shoots)
Pinching/pruning – removing terminal bud
Stems
Modified stems• Runner or stolin
– Aspen, strawberries, grass– Grow on surface– For asexual reproduction
• Rhizome– Iris, ginger, potato, onion– Grow underground– Store food & DNA for new plant– Tuber: end of rhizome
• Bulb – underground shoot– Onion – storage leaves
C. Leaves◦ epidermis of underside interrupted by stomata
(pores)◦ Mesophyll: ground tissue between upper/lower
epidermis◦ Parenchyma: sites of photosynthesis◦ Cuticle: waxy layer
Three Tissue Systems
A. Dermal Tissue• Single layer, closely packed cells that cover
entire plant• Protect against water loss & invasion by
pathogens• Cuticle: waxy layer• Epidermis, periderm
B. Vascular Tissue
• Continuous throughout plant• Transports materials between roots & shoots
1. Xylem: transport H2O and minerals up from root
2. Phloem: transports food from leaves to other parts of plantstele
C. Ground Tissue
• Anything that isn’t dermal or vascular• Function: storage, photosynthesis, support• Pith: inside vascular tissue• Cortex: outside vascular tissue
III. Cell TypesA. Parenchyma: most abundant
Perform metabolism, synthesizes & stores organic products
B. Collenchyma: grouped in cylinders, support growing parts of plant
C. Sclerenchyma: rigid support cellD. Xylem: water conduction
Tracheids, vessel elements – dead, tubular, elongated cells
E. Phloem: sugar, organic cmpd. conduction Sieve tubes, plates, companion cells – alive
cells which aid movement of sugar
PARENCHYMA CELLS
Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm
80 µmCortical parenchyma cells
Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM)
COLLENCHYMA CELLS
SCLERENCHYMA CELLS
SUGAR-CONDUCTING CELLS OF THE PHLOEM
WATER-CONDUCTING CELLS OF THE XYLEM
5 µm
Fiber cells (transverse section from ash tree) (LM)
25 µm
Sclereid cells in pear (LM)
Cell wall
Sieve-tube members:longitudinal view
30 µm
15 µm
Companioncell
Companioncell
Sieve-tubemember
Plasmodesma
Sieveplate
Sieve plate with pores (LM)
Nucleus
Cytoplasm
Sieve-tube members:longitudinal view(LM)
Vessel elements withperforated end walls
Vesselelement
Tracheids
Pits
Tracheids and vessels(colorized SEM)
TracheidsVessel 100 µm
Primary and Secondary Growth(apical vs. lateral meristems)
Concept 35.3 Primary growth lengthens roots and shoots
Root cap: protects meristem as it pushes through soil; also secretes polysaccharide lubricant
Zone of Cell Division: apical meristem; new cells produced
Zone of Elongation: cells elongate; push root tip ahead
Zone of Maturation: growth & differentiation complete; fully mature cells
Root Hairs
Concept 35.4 Secondary growth adds girth to stems and roots in woody plants
• Involves lateral meristems– Vascular cambium: produces secondary xylem
(wood)– Cork cambium: produces tough covering that
replaces epidermis• Bark = all tissues outside vascular cambium