Marine Plants - 1 Marine plants - Unlike the terrestrial...

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2 Marine plants - Unlike the terrestrial environment – the majority of primary productivity in the marine environment is not from plants – but photosynthesizing bacteria, single-celled algae. - Multi-cellular algae (i.e. seaweeds) also play a (lesser) role in primary production, but can still provide an important habitat for marine organisms - As noted before multi- and single-celled algae are considered to be members of Kingdom: Protista not kingdom: Plantae . NB – some biologists consider algae to be members of Plantae - There are also important marine plant species – which again can be food sources or habitats for some marine species - Common terrestrial plant groups are actually sparse or absent in the marine environment
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3 Multicellular algae: Seaweeds Seaweeds are sometimes refered to as MACROALGAE (as opposed to MICROALGAE covered last lecture) or MACROPHYTES Seaweeds are multi-cellular and eukaryotic, but there structure is more complex than unicellular algae They have a variety of adaptations to cope with the marine environment – e.g. specialized holdfasts in rocky shore seaweeds to withstand wave action The multicellular nature of seaweeds also gives them some advantages over single celled algae – development of specialized structures and the ability to be both attached to the sea bed (where nutrients are more abundant) and grow towards the surface (where light is more abundant) – i.e. best of both worlds
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5 Seaweeds structure Seaweeds do not have true stems, leaves, roots or flowers The entirety of a seaweed is called a THALLUS (pl. thalli) whether its just a filament or a giant kelp The leaf-like flattened part = BLADE Also the upper and lower surface of the blade is identical – unlike true leaves These are not true leaves as they lack veins – but they are the site of most photosynthesis The thin, flattened shaped allows more surface area exposed to sunlight and aid in the penetration of light through the blade
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6 Seaweeds structure The stem like structure is called the STIPE The root like structure attaching the seaweed to its substrate = HOLDFAST Holdfasts don’t penetrate the substrate (unlike roots) Holdfasts do not attach well to soft surfaces – usually rocky shore and seabed They also do not absorb nutrients like roots absorption of water and nutrients occurs via the surface of the whole thallus The stipe and the hold fast also have no specialized cells or structures to transport water or nutrients (no xylem or phloem) photosynthesis occurs in these structures as well causes limited distribution and importance to primary production
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7 Pneumatocysts The ‘bubble’ like structures in some seaweeds are called PNEUMATOCYSTS The gases in these bladder-like structures include toxic carbon monoxide These built in floats give buoyancy to the seaweed blades, lifting them closer to the surface of the water – increasing the amount of light the blades receive
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9 Types of seaweed There are three types of seaweed
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This note was uploaded on 01/23/2012 for the course BIOL/EVPP 449 at George Mason.

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Marine Plants - 1 Marine plants - Unlike the terrestrial...

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