MARCH, ROBERT H.1 and LYNN G. CLARK2.* 1Iowa State University, Department of Botany, 335 Bessey Hall, Ames, IA 50011; 2Iowa State University, Department of Botany, 345 Bessey Hall, Ames, IA 50011. - Fusoid cells in bamboos and basal grasses (Poaceae): source of enhanced enlightenment?
Fusoid cells are large, gas-filled, thin-walled mesophyll cells of
previously unknown function that occur within the basal grasses and
bamboos. Study of sun-shade leaf variation in three woody bamboo
species revealed not only the expected general suite of adaptations
(thicker, smaller sun leaves with closer vein spacing, and thinner,
larger shade leaves with wider vein spacing), but also that at least
in some species fusoid cells develop normally in shade leaves but do
not develop in sun leaves. Presence of fusoid cells is associated with
broad leafed, forest-dwelling grasses, but sun-shade differences in
the development of fusoid cells were noted even within an individual
plant, indicating an environmental as well as a genetic component to
their development. This strong correlation between shade and the
development of fusoid cells suggests a possible role of fusoid cells
in light distribution within shade leaves. Our data showed that leaves
with normal gas-filled fusoid cells absorbed more light than those
infused with mineral oil, supporting the novel proposal that one
function of fusoid cells is to increase light absorption through the
mechanism of intracellular reflectance. Further investigation should
be addressed to quantifying the enhanced light absorption in leaves
containing fusoid cells and to assessing the taxonomic distribution of
facultatively occurring fusoid cells.
Key words: bamboos, fusoid cells, light trapping, Poaceae, sun-shade leaf anatomy