The Plant Body. Why are plants so vital? Because Plants are Producers. Van Helmont - 1648.
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Transcript of The Plant Body. Why are plants so vital? Because Plants are Producers. Van Helmont - 1648.
The Plant Body
Why are plants so vital?Because Plants are Producers.
Van Helmont - 1648
Commonly used and abused chemicals substances from plants
• caffeine in coffee• theophylline in tea• theobromine in chocolate• nicotine in tobacco• cocaine from coca plant leaves• THC in Cannabis• and many other narcotic and psychoactive
substances
Cooksonia – 408 MYA
Plant Tissue Types
• Meristematic tissue - site of growth in plant; origin of the other tissue types
• apical meristems - site of primary growth; lateral meristems - site of secondary growth
• Dermal tissue system - the outer protective covering of the plant
• Vascular tissue system - comprises the xylem and phloem - it is embedded within the ground tissue system – xylem forms wood in woody plants
• Ground tissue system - the inner supportive tissues of the plant – pith in herbaceous plants
Primary Plant Growth
• Primary growth originates in the apical meristems and results in increases in length - tissues originating from primary growth make up the primary plant body (primary xylem, primary phloem, etc) - many vascular plants consist entirely of primary tissues
Secondary Plant Growth
• Secondary growth originates in the lateral meristems and results in increases in width - there are two lateral meristems
• Vascular cambium which produces secondary vascular tissues - secondary xylem to the inside and secondary phloem to the outside
• Cork cambium is outside the vascular cambium - it forms periderm, which is made of cork tissue - the periderm replaces the epidermis as the dermal tissue system of the plant
Xylem tissues• Secondary xylem is dead at maturity and transports water
essentially through a hollow tube - angiosperms have tracheary cells are called vessels and tend to have flattened ends, as well as tracheids
• in gymnosperms the tracheary cells are called tracheids and usually sharply tapered
• eventually the xylem becomes full of sap and is no longer used for water transport, then functions in support and forms wood
• Phloem cells are called sieve tube elements because of the sieve like plates at the end of the cells - they are alive at maturity but are crushed as the plant grows in diameter and must be continually replaced
• Some sieve cells have companion cells which govern transport of material through the sieve
Xylem –VesselsandTracheids
Phloem – sieve elements
Garlic Roots
Fibrous Tap
Varieties of Root Systems
Lateral growth of a willow root