Monterey Bay Aquarium Research Institute
Marine Botany

Blades

kelp forest view

The Macrocystis pyrifera blades are the real workhorse of the kelp.  It is the site where most of the sun's light energy is captured and converted into sugar.  This process is known as photosynthesis, capturing light to produce adenosine triphosphate (ATP), and then using this ATP to produce six-carbon sugar molecules.

Photosynthesis 6CO2 + 6H20 + light -> C6H1206 + 6O2

The sugars produced are then used by the alga for energy.  These sugars are transported down the stipe to other areas of the kelp, juvenile fronds, and the holdfast where they may depend on the blades for energy.  When nitrogen is in low concentrations in the water, giant kelp has the ability to store nitrogen to be used up to two months later (Connor 2001).

kelp blades

Pictured above is the terminal region of a frond, known as the scimitar blade, due to its similarities.  This is the region where new blades are formed, slowing growing and tearing itself off from the scimitar blade.

scimitar blade

Pictured above is a scimitar blade from the Gilbert M. Smith Herbarium.  This sample was preserved on an herbarium sheet.  Notice the small pneumatocysts forming at the base of the scimitar blades.  These blades may reach lengths of 40cm (Bold 1978).

internal structure

Above is a cross section of a blade taken through the microscope at 40X magnification.  The darker regions in the image are the densely packed chlorophyll regions where much of the photosynthesis occurs.

Copyright 2001:  James Lopez

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