Abstracts of Papers - Harvard Forest - Harvard University

Parthenium argentatum, Gray (guayule), a north Amer-
ican desert shrub, contains large quantities of high
quality rubber. Unlike Hevea, P. argentatum stores
rubber within parenchymatous cells. The first
appearance of rubber occurs in the epithelial cells
of the primary and secondary resin canals of six to
eight month old plants. The morphology of these
resin canals has been previously described. Bio-
regulators, such as 2-(3,4-dichlorophenoxy)-triethyl-
amine (DCPTA), are known to increase the total rubber
content of P. argentatum. Experimental P. argentatum
plants were treated by spraying with a solution of
50 ppm DCPTA and 250 ppm Ortho X-77 (a wetting agent)
while control plants were sprayed with the Ortho X-77
only. An analysis was made of the effects of these
treatments on resin canal morphology, including resin
canal number and size and epithelial cell number and
size.
WILDER, GEORGE J.* and PHILIP B. TOMLINSON.
Harvard Forest, Harvard University,
- Functional and systematic-anatomical
Petersham,
studies
MA.
of
laminae of the Cyclanthaceae. I. Epidermis.
Cyclanthaceous laminae are normally hypostomatic and
their abaxial epidermis tends to exhibit longitudinal
bands either with or without stomata. In the subfamily
Carludovicoideae bands of the abaxial epidermis
without stomata develop over fiber bundles, abaxial
ridges, and sometimes veins; bands of epidermal expansion
cells, also without stomata, occur in each
epidermis above or below adaxial and abaxial ridges,
and over expansion tissue of the mesophyll. Stomata
are either functional or nonfunctional. The pore of
a functional stomate extends between inner and outer
ledges of the guard cells, and consists of a one or
two-chambered front cavity, back cavity, and central
pore. Both guard cells of a stomate may be connected
by two obvious polar perforations. Nonfunctional
stomata exhibit collapsed guard cells with or without
lignified walls, and sometimes also have substomatal
chambers occluded by the abnormal enlargement of adjacent
cells, e.g. subsidiary cells. Subsidiary
cells and undifferentiated epidermal cells may overlap
one another in ways that appear mechanically advantageous.
Each stomate is typically associated
with fo'ur subsidiary cells which may differ from undifferentiated
epidermal cells according to position,
shape, non-nuclear contents, nuclear size, cuticular
ornamentation, and cell walls. In each subfamily epidermal
cells proper may exhibit lumen papillae and
also cuticular ornamentation (papillae, ridges). An
epidermis sometimes has substantial dorsiventral symmetry.
In addition, one can sometimes determine (a)
whether a noncostal fragment of epidermis belonged to
the abaxial or adaxial leaf surface, (b) what types of
cells or structures it occurred over, (c) which are
its proximal or distal ends and, hence, (d) its right
and left sides. Systematic conclusions w'll be given.
WILDER, GEORGE J.* and PHILIP B. TOMLINSON.
Harvard Forest,
01366.
Harvard University, Petersham, MA
- Functional and systematic-anatomical studies of
laminae
veins.
of the Cyclanthaceae. II. Mesophyll and
The mesophyll contains hypodermal cells, bundle
sheath cells, epithelial cells of mucilage cavities
(certain Garludovicoideae), and laticifer sheaths
(Cyclanthus), which exhibit common features and,
hence, are categorized together as "boundary layers"
The remaining cells of the mesophyll between boundary
Developmental and Structural Section 35
layers comprise adaxial, abaxial, and sometimes mid-
dle regions. Depending on the species, ordinary pa-
renchymacells between boundary layers are either mono-
morphic or dimorphic; where dimorphic, one of the two
types - generally, with larger and more concentrated
chloroplasts - is interpreted as more specialized for
photosynthesis. Within ordinary parenchyma cells,
tannin or tannin-like material may comprise very ela-
borate star figures which are refractile in preserved
material. In certain species of Carludovicoideae the
mesophyll contains thin-walled dead cells, and pres-
ence of these cells is of particular interest because
of the occurrence of lysigenous intercellular spaces
in Cyclanthus. Fibers of the mesophyll tend to differ
from phloem fibers in ways which suggest that these
two cell types are specialized to contribute tensile
strength and rigidity, respectively. Raphide sacs
and sometimes also styloid sacs occur, and what may
superficially appear as one raphide is often com-
pound, comprised of four or more.subunits. Veins of
an inter-ridge area (Carludovicoideae) or between
principal veins (Cyclanthus) are of different orders
of diameter, and vein number increases exponentially
in increasingly higher orders. The smallest sieve
elements in a vein tend to be gro5uped into one or two
poles on the adaxial side of the phloem. Systematic
conclusions will be presented.
WISNIEWSKI, MICHAEL*, A. LINN BOGLE and C.L. WILSON
Department of Botany and Plant Pathology, University
of New Hampshire, Durham, 03824. Appalachian Fruit
Research Station, USDA, Kearneysville, WV 25430 -
The Developmental Anatorny of Wound Response in
Current Year Shoots of Prunus persica L. Batsch.
The ability of peach trees to effectively compart-
mentalize wounds may play an important role in resis-
tance to Cytospora canker. Little information exists
in this area for peach. Therefore, an anatomical in-
vestigation of wound response was undertaken. Current
year shoots of three cultivars were wounded by making
a scratch with a fine forceps. Samples were collected
periodically and examined using light microscopy and
SEM. Initial wounding penetrated into the cortec and
occasionally to the vascular cambium. Within two
weeks, a well differentiated wound periderm was es-
tablished from undifferentiated phloem and cortical
cells. Normal xylem and phloem production was replac-
ed in a wide area of the stem by parenchymatous tissue.
These cells became hypertrophied and in some areas
degenerated and formed gum cysts. Phellem cells pro-
duced by the wound periderm became quickly and heavily
suberized in contrast to normal epidermal cells. A
region exhibiting strong autofluorescence was observ-
ed at the radial edge of the wound periderm. Within
four weeks, periderm formation was initiated in un-
injured portions of the stem (i.e,, the wound peri-
derm acted as a center for and instigated premature
periderm development in the rest of the stem). There
was also an accumulation of druses in the cortical
cells of the wound area. An EDXA of these crystals
identified the presence of calcium. No major differ-
ences between cultivars were observed. Observations
indicate that periderm formation occurs at a relative-
ly fast rate compared to rates reported for other
species and that the degree of gum cyst or gum dUCt
formation is proportional to the severity of the wound.
WITTLER, GEORGE H.* and JAMES D. MAUSETH. Department
of Botany, University of Texas, Austin, TX
78712. - The ultrastructure of developing
ducts i n Mammill 1ari a heyderi ( Cactaceae )
Electron microscopy was used to investigate
latex
early