Abstracts of Papers - Harvard Forest - Harvard University

in the concept of "serial homology", and the more
concise notion of strict homology which (by defini-
tion) is due to descent. A historical perspective is
particularly illuminating, especially as the basic
principles of comparative morphology are largely
conceived in a pre-evolutionary environment. Em-
phasis will be placed on developmental analysis in
comparative morphology as a basic process in the
generation of the modular organism. Knowledge of
development can frequently illuminate comparative
analysis. Examples will be cited where the organiza-
tional plasticity almost defeats the possibility of
evolutionary morphological analysis in modular organ-
isms.
W. H. WAGNER, JR., Department of Botany, University
of Michigan, Ann Arbor, Michigan 48109. -
Homology and the early
plants.
diversification of vascular
Primitive vascular plants are the ones that first appeared
in the fossil record, that possess simple life
cycles,and are most similar to the outside group, the
bryophytes. Because of their diversity, homology of
even major organs has been controversial. Theories
like the Stelar Theory or the Telome Theory try to
fit the morphics of plants into preconceived molds
Objectivity is best accomplished by using classical
tests of position, ontogeny, mature structure, and
absence of intermediates. Evidence of early diversification
of vascular plants comes from cladistic analysis
of living groups, psilotopsids, lycopsids,
equisetopsids, and polypodiopsids, together with the
fossil remains of trimerophytes, zosterophytes, and
rhyniophytes, a motley assemblage. Our problem is
to connect different organs in different groups, because
there are such large gaps, and intermediate
stages or trends are lacking. How teratology fits
into this is a question. In addition to varlous tissue
types, the major organs are discussed:stem, root,
leaf, sporangium, spore, gametophyte, gametangia,
gametes, embryo, and foot. Because of homoplasy,
homology is, by itself, not necessarily a criterion
of relationship. At the tissue level, the stele provides
a challenge; at the organ level, the foliar
appendages. Parsimony suggests that at least in the
case of the leaf, all of the appendages were originally
emergences. The position of sporangia, so fundamental,
apparently, in the early differentiation
of vascular plants, is a good example, of the absence
of intermediates, suggesting abrupt, rapid changes.
There is a spectrum of degrees
organs of early vascular plants
to very questionable.
of homology of the
-- from very obvious
Poster Session
BASILE, DOMINICK V. and MARGARET R. BASILE
Department of Biological Sciences, H. H.
Lehman College of CUNY, Bronx, N.Y. 10468.
- Auxin antagonist-induced desuppression
of leaf primordia of Plagiochila arctica
(Hepaticae): Possible integration of
auxin, ethylene and hydroxyproline-alterable
proteins in correlative control of
cellular suppression.
Two inhibitors of auxin transport, triiodobenzoic
acid (TIBA) and N-l-naphthylphthalamic
acid
auxin action, i -
(NPA), and an inhibitor of
(p-chlorophenoxy) isobutyric
acid (PCIB), induced the same kind of pheno-
Developmental and Structural Section 13
variation in Plagiochila arctica Bryhn &
Kaal. (Hepaticae) as do antagonists of ethy-
lene synthesis/action and antagonists of
hydroxyproline-protein (hyp-protein) syn-
thesis. This indicates that the two phyto-
hormones and a cell surface protein sensi-
tive to antagonists of hyp-protein synthesis
play an integrated role in the correlative
control of cellular suppression - primordium
development. Auxin-induced ethylene syn-
thesis and ethylene-induced cell surface
hydroxyproline protein deposition correlated
with suppressed development have been re-
ported byothers, previously. This, however,
is the first experimental evidence to impli-
cate all three molecules, two phytohormones
and a cell surface glycoprotein, in the same
morphoregulatory system. This correlative
control system conceivably plays an impor-
tany role in other, if not all, groups of
land plants (Embryophyta).
CAESAR, J. C. AND A. D. MACDONALD*. Department
of Biology, Lakehead University, Thunder Bay,
Ontario. P7B 5EI.
- Comparison of early growth of vegetative and
reproductive short shoots of Betula papyrifera.
This study shows the cost to short shoot growth of
female inflorescence development. Expanding and
flushing short shoot buds were collected from mature
trees from April-June 1982. Quantitative analyses
were made on fresh and FAA-fixed material for
relative growth rates (RGR) of leaves and buds,
specific leaf area (SLA), leaf area ratio (LAR), leaf
area (LA) and number of leaf side nerve pairs (SNP).
Material was partially dissected to determine whether
the bud was reproductive or vegetative. Short shoot
buds may be vegetative or may bear a female
inflorescence; these buds may be proximal on a long
shoot or terminal on a short shoot. Axillary short
shoot buds flush later than 2-4 year old short shoot
terminal buds, which flush later than 5-10 year old
shoots. Mean RGR of 5-10 year old short shoot buds
is greater than that of younger short-shoot buds. It
is suggested that older short shoot buds are
relatively autonomous and that the flushing long
shoot exhibits an inhibitory influence on the
proximal axillary buds and possibly on young short
shoot terminal buds. Reproductive short shoots diffr
from vegetative short shoots in that they have lower
LAR's and leaf RGR's, higher SLA's, smaller LA's,
fewer SNP's and they seem to grow more in length
than in width. These findings are related to
reproductive cost. The developing inflorescences
act as preferred 'sinks' for resource allocation.
CECICH, ROBERT A. Forestry Sciences Laboratory,
P.O. Box 898, Rhinelander, WI 54501 -
Histochemical and ultrastructural changes in
microsporangia of jack pine during the winter.
The development of jack pine (Pinus banksiana Lamb.)
microsporangia from October to April was investigated.
DNA, RNA, and protein content of sporogenous
cells was measured with a microdensitometer at
monthly intervals. DNA was unreplicated (2c) until
March when DNA synthesis was first noted, coinciding
with a loss of condensed chromatin. Protein staini
ng i ncreased i n Apri . RNA stai-n i ng i ncreased i n
December, followed by a loss of staining in January.