Dr. Geiger et al., EFFECT OF ENVIRONMENTAL-FACTORS ON WHOLE-PLANT ASSIMILATE PARTITIONING AND ASSOCIATED GENE-EXPRESSION, Journal of Experimental Botany, 47, 1996, pp. 1229-1238
Partitioning of assimilated carbon among sink organs is a critical fac
tor that controls the rate and pattern of plant growth. Time-course me
asurements of plant and organ growth rates are useful for determining
how regulation of carbon partitioning controls plant growth. Measuring
growth rates over a 24 h period reveals the current pattern of carbon
partitioning that can be used to predict growth rates of specific sin
ks. Comparison of growth rates among sinks under defined conditions ca
n point out key factors that regulate partitioning of recently assimil
ated carbon among sinks. Internal control of carbon partitioning by de
velopmental programmes regulates the timing and site of carbon distrib
ution among developing parts, thereby establishing the adaptive traits
of a species, cultivar or transgenic construct. Regulation of partiti
oning in response to environmental factors establishes or restores all
ometric growth among plant parts and functional balance between the su
pply and use of carbon. Environmental stress often restricts resource
availability while successful acclimation sets in motion processes tha
t restore the supply. A key mechanism contributing to regulation of ca
rbon partitioning is an expression of genes that control activity of t
he enzymes which initiate sucrose metabolism at specific sites and sta
ges of ontogeny.