PNL Volume 15 1981
RESEARCH REPORTS
15
FUNCTIONAL STOMATA ON THE PODS OF THE ARGENTEUM MUTANT OF PISUM SATIVUM
Donkin, M. E. , D. N. Price, and E. S. Martin
Plymouth Polytechnic, Plymouth, U. K.
Smith, C. John Inne3 Institute, Norwich, U. K.
Hull, T. Rumleigh Experimental Station, Bere Alston, U. K.
Many fruits, including pods of the Leguminosae, have stomata on
their outer surface; however, very little is known about the movements
and functions of the stomatal apparatus. Some stomata may open and
close normally but many remain open permanently, especially when they
are present in the inner epidermis of fruits. The function of stomata
on pods such as those of Pisum sativum is of great importance when con-
sidering the carbon economy of the pod.
Recently a mutant of Pisum. Argenteum (Arg.), was described (2,3),
the leaves of which have an easily detachable epidermis. This makes it
ideal for the study of stomatal behavior. We have recently investigated
the behavior of stomata on the upper and lower epidermis of this mutant
(1), and we were also interested in the behavior of stomata on the
epidermis of the Arg pod. The pod epidermis does not detach as readily
as that of the leaves but it appears to be easier to remove from young
pods of Arg than from those of other Pisum lines.
The in situ behavior of the pod stomata was investigated in two
ways. The first experiment (Table 1) was a "split pod" experiment in
which pods were removed from the plant, split in half, and the seeds
were removed. Each half was kept either in the light or dark for 4
hours and at the end of this period strips were removed from the pods
and the stomata] apertures were determined under the microscope.
Table 1 shows that in this type of experiment the stomata were slightly
more open in the light than in the dark (about 1 mkm). The second ex-
periment involved taking epidermal samples from pods still attached to
the plant at various times in a light/dark cycle; stomatal apertures
were determined by microscopic measurements. Table 2 shows that under
these conditions the stomata on the pods had a wider aperture in the
light period than in the dark period.
Table 1. Stomatal apertures on "split pods" in the light or dark. Three
8-day old pods were taken from the plant and split into two
halves. Each half was placed onto water, inner surface down,
in a Petri dish. One dish was kept in the light (140 mkmol
m-2 s-1) 400-700 nm, and the other in the dark for 4 hr at
20 C. At the end of this period three strips of epidermis
were taken from each pod half and 10 apertures were measured
on each strip (90 apertures in total per treatment). The
results were analyzed by a paired t-test and showed a sig-
nificant difference between light and dark (P=0.025, df=2).
