Introduction to Plants Kingdom Plantae Plants Cell wall

Introduction to Plants Kingdom: Plantae ØPlants: �Cell wall �Autotroph (photosynthesis) �Multi-cellular Ø 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, • Eg. bean, pea, rose, sunflower bamboo

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

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

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

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

WATER-CONDUCTING CELLS OF THE XYLEM PARENCHYMA CELLS Vessel Parenchyma cells in Elodea leaf, with chloroplasts (LM) Tracheids 100 µm 60 µm Pits COLLENCHYMA CELLS 80 µm Cortical parenchyma cells Tracheids and vessels (colorized SEM) Vessel elements with perforated end walls Tracheids SUGAR-CONDUCTING CELLS OF THE PHLOEM Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM) SCLERENCHYMA CELLS Sieve-tube members: longitudinal view (LM) 5 µm Companion cell Sclereid cells in pear (LM) Sieve-tube member Plasmodesma 25 µm Sieve plate Cell wall Nucleus Cytoplasm Companion cell Fiber cells (transverse section from ash tree) (LM) Sieve-tube members: longitudinal view 30 µm 15 µm Sieve plate with pores (LM)

Primary and Secondary Growth (apical vs. lateral meristems)

Concept 35. 3 Primary growth lengthens roots and shoots Root Hairs Zone of Maturation: growth & differentiation complete; fully mature cells Zone of Elongation: cells elongate; push root tip ahead Zone of Cell Division: apical meristem; new cells produced Root cap: protects meristem as it pushes through soil; also secretes polysaccharide lubricant

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