Pk. Diggle, EXTREME PREFORMATION IN ALPINE POLYGONUM-VIVIPARUM - AN ARCHITECTURALAND DEVELOPMENTAL ANALYSIS, American journal of botany, 84(2), 1997, pp. 154-169
Preformation, the initiation of organs one or more years prior to matu
ration and function, is reported to be common and crucial for plant su
rvival in arctic and alpine environments, yet the phenomenon is remark
ably little studied. in order to understand the role of preformation i
n the ecology and evolution of tundra species. this investigation take
s a developmental and architectural approach to the analysis of plant
growth and reproduction in the alpine perennial Polygonum viviparum L.
Analyses show that the extent and duration of preformation in P., viv
iparum are extraordinary. Four years are required for each leaf and in
florescence to progress from initiation to functional and structural m
aturity. This single salient feature of development has profound conse
quences for basic architecture, dynamics of resource allocation, and t
he timing of plant responses to environmental variation. As a conseque
nce of the protracted duration of leaf and inflorescence development,
five cohorts of primordia, initiated in successive years, are borne si
multaneously by an individual plant. In the year prior to maturation l
eaves reach 30% of their maximum size, and the maximum potential repro
ductive output of each inflorescence is determined. Thus, developmenta
l processes that affect final morphology and resource allocation occur
at least 1 yr before functional maturity. From the developmental and
architectural models constructed for P. viviparum, a I-yr delay in mea
surable plant responses to environmental variation is predicted. The m
odels also apply generally to arctic and alpine species and provide a
mechanistic explanation for observed patterns of productivity at the c
ommunity and ecosystem scale.