MELOCHE, CHRISTOPHER G.* AND PAMELA K. DIGGLE. Department of Environmental Population and Organismic Biology, University of Colorado, Boulder, CO 80309. - Patterns of carbon allocation in Acomastylis rossii(Rosaceae) an alpine plant exhibiting extreme preformation.
Extreme preformation, the initiation of leaves or inflorescences more
than one year before maturation and function, is common in arctic and
alpine habitats. This extended pattern of development provides a
potential means to alleviate an apparent asynchrony between carbon
supplied by photosynthesis in the summer and carbon demanded by growth
in the spring. The cost of storing carbohydrates for the next year’s
spring growth may be reduced by allocating carbohydrate directly from
photosynthesizing leaves to the growth of preforming organs which will
mature in subsequent years. Allocation of resources to preforming
organs has, however, previously been unstudied in plants with
multi-year patterns of preformation. Populations of A. rossii
in the southern Rockies have been observed to initiate leaves and
inflorescences two years before the year of maturation and function.
Allocation to preforming organs in A. rossii was studied by
means of a labeled carbon pulse chase experiment. Plants were labeled
by exposure to a 13CO2 enriched atmosphere for
one photoperiod during the 1998 summer growing season. Plants were
then harvested and analyzed by mass spectrometry over the course of
the subsequent thirteen months to determine the distribution of the
13C label. During the summer growing season carbon is
allocated directly to preforming organs and rhizomes from the mature
leaves. Additional allocation of carbohydrate into preforming organs
occurs in autumn after these leaves have stopped photosynthesizing.
Existing preformed organ primordia do not subsequently receive
additional inputs of labeled carbon from rhizomes in the second year
of development. Newly initiated organ primordia initiated in the
second year do not receive any of the labeled carbon initially
allocated to storage in the rhizome the previous year.
Key words: Acomastylis rossii (Rosaceae), alpine, carbon allocation, preformation