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Chapter 3

BIO204 CH36 - Plant Form and Function - Lecture 2
BIO204 CH36 - Plant Form and Function - Lecture 2

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University of Toronto Mississauga
Sanja Hinic- Frlog

2 (CH36 - Plant Form and Function) October-04-13 8:42 PM Indeterminate growth - plants grow throughout their lives Plant Form: Themes with Many Variations Resources: Carbon dioxide, light, water (electron source) Root system - gathers nutrients and water below ground Shoot system - harvests light and CO2 Herbaceous plant - seed plant that lacks wood KEY CONCEPT 1 Plant Form - Vascular plants consist • Root system ○ anchors the individual ○ Uptake of water and nutrients ○ absorb water and ions, conduct water and selected ions to the shoot, store material in the shoot Taproot - vertical section Lateral roots - horizontal •  Shoot system ○ Uptake of carbon dioxide ○ Absorption of light energy (sunlight) ○ Stem - at the tip is apical bud, consist of node (where leaves are attached) ○ Internode ○ Axillary bud - may develop into branch •  Dynamic systems • grow and change throughout the life of the plant • Modifications and adjustments occur in response to environment Diversity of root systems can be analyzed in 3 levels: 1. morphological diversity among species a. Perennial root systems- live for many yrs b. Natural selection favored diversity to minimize competition for water/ nutrients e.g. Morphological diversity in plant roots e.g. Morphological diversity in plant roots • Similar functions in all plants • Highly diverse in structure e.g. depths and widths • Consequences of the diversity of root systems (1) plants can coexist in the same area with less competition for water and soil resources; (2) most individuals can survive drought years. Diversity between species • Morphological diversity between species in root systems in prairie plants • alleviation of competition for water and nutrients Tap root - digs really deep It can coexist with other plants 2. Phenotypic plasticity - roots are plastic or changeable, depending on environmental conditions (they tend to actively grow where resources are abundant) 3. Modified roots: a. Adventitious root - develops from shoot system instead of root system Diversity of shoot systems can be analyzed in 3 levels: 1. Morphological diversity - allows plant of different species to harvest light at different locations and thus minimize competition - Allows them to thrive at different array of habitats - Several species grow as compact forms called rosettes 2. Diversity within species (phenotypic plasticity) in the shoot of maple - Response to variation in light availability - Response of shoot to changes in environmental conditions during lifetime of plant No competition for light Excessive use of old habitat by using the large crown More straight • Leaves exhibit phenotypic plasticity • E.g. large, broad shade leaves and smaller sun leaves in oak (thickness is different too) 3. Modified shoots - Cactus stem (leaves are modified into spines - protective structures) - Stolons - Rhizomes - Tubers - Thorns *Leaf - Blade - expanded portion - Petiole - stalk 1. Morphological Diversity - is for maximization of efficiency of light capture - Arrangement of leaves: opposite, whorled, alternate, rosette - Water is often in short supply environments (deserts or cold habitats) - Leaves go through transpiration (evaporation process) 2. Phenotypic plasticity - Grown in shade (large surface area) vs. grown in sun (smaller surface area) 3. Modified leaves - Onion leaves store food - Aloe vera leaves store water - Pea tendrils aid in climbing - Poinsettia leaves attract pollinators - Pitcher plant leaves trap insects - Flowerpot plant leaves collect soil KEY CONCEPT 2 KEY CONCEPT 2 Primary growth • Division of cells at tips of roots & shoots from apical meristems - Only found in tips of roots/ shoots • Extends body - Elongation is primary growth Differentiation into 3 primary tissue systems • Protoderm • Ground meristem - undifferentiated cells • Procambium Meristems • undifferentiated cells • mitosis and cell division result in new cells Apical meristems • Tip of root and shoot • Extension of plant body outward in the process of primary growth Primary Growth produces the Primary Plant Body • Apical meristemsin root and shoot give rise to three distinct populations of cells ○ Protoderm - dermal tissue system (epidermis) ○ Ground meristem - ground tissue system ○ Procambium - Vascular tissue system Blueprint – determine the structure and function of the plant body Organization of primary root system
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