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Lecture 12

BIOA02 LECTURE 12: Plant Life on the Edge

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Biological Sciences
Mary Olaveson

BIOA02 Lecture 12 Plant Life on the EdgeFebruary 03 2012 several environmental conditions which make plant life hard ie short summers in polar regions frost dry desert heatdrought in salt water toxic soils heavy metals low light and in bogs nutrient poor perpetual inundation overabundance of freshwatermain focus of lecture will be on perpetual inundation because its the most common in Southern Ontarioin Southern Ontarioabundance of lakes and pondssome plants have leaves on water surface or some have them submergedlimitation of plants in freshwater decreased carbon dioxide much lower than in air oxygen light attenuates very quickly as you go deeper in water column nutrients much lower water current can be so strong so plants have to make sure they dont get torn apartTrue hydrophytes submerged plantsplants which spend all of their life cycle underneath the waterdissected narrow leavesadaptations needed to make them true hydrophytes poorly developed xylemwater just enters throughout the plant almost no mechanical strengtheningsupported by body of water because plants have hard maximum surface to volume ratio time accessing gases because of the small amounts of gases in waterthin cuticle no stomatesno risk of running out of wateradapted intercellular air spacedistribution of air spaceReduced Xylemno need for vast xylem system because of abundance of waterie water lily only has two individual cells of xylem making up the tubing system within the plantLittle Mechanical Supportwater keeps plants upright on land plants the support is made up of vascular bundles hydrophytes have one vascular bundle usually in the centre minimizing the amount of sclerenchyma and collenchyma madevascular bundle is located in centre because it minimizes the wearmore pliable and less prone to and tear inflicted by water currents be torn apartthe leaves also are threadlike or strongly dissectedsome plants have net like structure that allows water to go through holes to decrease damage of water currentMaximum SurfacetoVolume Ratio
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