Introduction to Plants Kingdom: Plantae  Plants:  Cell wall  Autotroph (photosynthesis)  Multi-cellular  12 Divisions (Phyla)  Anthophyta = Angiosperms (flowering plants)  Largest # of species (~250, % plants)  Seed plants: product seed w/in a fruit  Key adaptations: flowers & fruits  Sporophytes are trees, shrubs, herbs that flower Monocots Dicots  2 main groups: Monocots & Dicots

Monocots vs. Dicots

MonocotDicot 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 Above ground Stems, leaves Underground (usually) Roots Underground (usually) Roots Shoot system Root system

A. Roots  Anchors plant, absorbs H 2 O & minerals, stores sugars/starches  Root hairs – tiny extensions of epidermal cells, increase surface area for H 2 O and mineral absorption  Mycorrhizae: symbiosis with fungi Root hairs

Fibrous RootsTaproots 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 H 2 O and minerals up from root 2.Phloem: transports food from leaves to other parts of plant stele

C. Ground Tissue Anything that isn’t dermal or vascular Function: storage, photosynthesis, support Pith: inside vascular tissue Cortex: outside vascular tissue

III. Cell Types A.Parenchyma: most abundant  Perform metabolism, synthesizes & stores organic products B.Collenchyma: grouped in cylinders, support growing parts of plant C.Sclerenchyma: rigid support cell D.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 µm Cortical 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 Companion cell Companion cell Sieve-tube member Plasmodesma Sieve plate Sieve plate with pores (LM) Nucleus Cytoplasm Sieve-tube members: longitudinal view (LM) Vessel elements with perforated end walls Vessel element Tracheids Pits Tracheids and vessels (colorized SEM) Tracheids Vessel 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