Extreme preformation in alpine Polygonum viviparum: an architectural and Developmental Analysis

Abstract

Preformation, the initiation of organs one or more years prior to maturation and function, is reported to be common and crucial for plant survival in arctic and alpine environments, yet the phenomenon is remarkably little studied. In order to understand the role of preformation in the ecology and evolution of tundra species, this investigation takes a developmental and architectural approach to the analysis of plant growth and reproduction in the alpine perennial Polygonum viviparam L. Analyses show that the extent and duration of preformation in P. viviparam are extraordinary. Four years are required for each leaf and inflorescence to progress from initiation to functional and structural maturity. This single salient feature of development has profound consequences for basic architecture, dynamics of resource allocation, and the timing of plant responses to environmental variation. As a consequence of the protracted duration of leaf and inflorescence development, five cohorts of primordia, initiated in successive years, are borne simultaneously by an individual plant. In the year prior to maturation leaves reach 30% of their maximum size, and the maximum potential reproductive output of each inflorescence is determined. Thus, developmental 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 1-yr delay in measurable plant responses to environmental variation is predicted. The models also apply generally to arctic and alpine species and provide a mechanistic explanation for observed patterns of productivity at the community and ecosystem scale.

Clonal integration of the stoloniferous herb Fragaria vesca from different altitudes in Southwest China

“…In inherently poor and stress affected habitats, such as high-salt meadows, selection may favor plants with weak plasticity in growth and morphology (Van Groenendael & De Kroon 1990;De Kroon & van Groenendael 1997;. Also, in cold tundra environments, individual phenotypic plasticity is predicted to be low (Grime 1977 ;Fetcher & Shaver 1990;Chapin et al 1993;Diggle 1997), probably because the cost of plasticity in growth and morphology in such environment are very high (Hutchings & De Kroon 1994). In alpine environments, in particular low soil temperature is the major constraint for the supply of plants with available nitrogen (Bliss 1971).…”

Experimental approaches to predicting the future of tundra plant communities

“…Synthesis I also indicated that a shift occurred over the first 3-4 years of warming from strong vegetative responses early on toward greater reproductive effort and success in the fourth treatment year (Arft et al 1999). These results were interpreted as reflecting a possible depletion of stored plant reserves or soil nutrients, so that sustained vegetative growth was constrained, while investment in reproduction was a secondary response reflecting increased production of flower buds in seasons prior to flowering (flower buds form one to several seasons prior to flowering in many tundra plant species : Sørensen 1941;Diggle 1997).…”

A developmental morphologist's perspective on plasticity

“…An extreme example is provided by the common developmental pattern known as preformation, the initiation of determinate structures (e.g., leaves, inflorescences, flowers) one or more growing seasons prior to their complete maturation and function (Halle´et al, 1978;Diggle, 1997a). As a result of this prolonged period of development (potentially spanning portions of at least 2 years), responses to environmental variation may be delayed significantly (Diggle, 1997a;Aydellote and Diggle, 1997;Geber et al, 1997). Preformation is common among temperate trees, shrubs and herbaceous perennials and is nearly ubiquitous among taxa of the arctic and alpine tundra (reviewed by Sørensen, 1941;Diggle, 1997a).…”

“…As a result of this prolonged period of development (potentially spanning portions of at least 2 years), responses to environmental variation may be delayed significantly (Diggle, 1997a;Aydellote and Diggle, 1997;Geber et al, 1997). Preformation is common among temperate trees, shrubs and herbaceous perennials and is nearly ubiquitous among taxa of the arctic and alpine tundra (reviewed by Sørensen, 1941;Diggle, 1997a). In Polygonum viviparum (Polygonaceae), a common component of many arctic and alpine plant communities, development of leaves and inflorescences requires 4 years from initiation to maturation (Diggle, 1997a).…”

“…Preformation is common among temperate trees, shrubs and herbaceous perennials and is nearly ubiquitous among taxa of the arctic and alpine tundra (reviewed by Sørensen, 1941;Diggle, 1997a). In Polygonum viviparum (Polygonaceae), a common component of many arctic and alpine plant communities, development of leaves and inflorescences requires 4 years from initiation to maturation (Diggle, 1997a).…”