In our environment, we are surrounded by plants,
our most abundant renewable resource.
My name is Debra Mohnen,
and in this presentation,
Melani Atmodjo and I
from the Complex Carbohydrate Research Center
at the University of Georgia
will summarize our current understanding
of plant cell wall structure and synthesis.
Each year approximately 100 billion tons
of carbon dioxide are fixed into biomass
with roughly one-third of that
produced by marine plants and microorganisms
and two-thirds from land plants.
plants use carbon dioxide and water
taken up from the environment
and energy from the sun to produce carbohydrates.
The bulk of that fixed carbon ends up in the plant cell walls.
Plant cell walls are the carbohydrate-rich
extracellular matrix that surrounds all plant cells.
Plant cell walls and plant cells vary in shape and structure
depending upon the cell type,
as can be seen in these micrographs.
Note the difference in shape and surface structure
of the epidermis of Arabidopsis sepals,
the leaf-like structure that supports petals,
on the upper left versus the epidermis
of petals on the upper right.
Furthermore, note the intricate branch structure
on the bottom left of single cell trichomes
versus the elongated and pitted structure
of pollen cells on the bottom right.
Finally, note the round structure
of suspension-cultured cells grown in liquid culture
on the bottom middle
versus the rigid and thicker wall structure
of the large xylem cells,
which make up water transporting vascular cells
and cells in wood.
Plant cell walls have diverse and critical functions in the plant
including providing structure to the plant and plant cells,
being involved in plant growth,
giving the plant flexibility,
as you can see when plants sway in the wind.
They provide hydration, as you may see when a seed germinates.
They are a reservoir of defense and signaling molecules,
and they provide cell adhesion between adjacent cells
and are involved in development.
If you look at the picture,
what you will see is the wild-type Arabidopsis plant on the left
compared to a mutant plant
that is mutant in one of the plant cell wall biosynthetic enzymes,
clearly showing that a knockdown in expression
of a wall biosynthetic enzyme
can lead to dwarfism.