6 The Significance of Assimilatory Starch
for Growth in Arabidopsis thaliana Wild-Type
and Starchless Mutants
W. Schulze and E.-D. Schulze
6.1 Introduction
Vegetative growth is generally assumed to reach maximum rates when
plants invest as much carbohydrate as possible in the growth of new leaves
(Monsi and Murata 1970; Schulze 1983). Only with new leaves are additional
production organs established which by compound interest contribute to
further growth (Harper 1989; Diemer et al. 1992). Growth rates are eventually limited by supply of resources, such as water and nutrients, or light in
the case of self-shading (Schulze and Chapin 1987). Storage of carbohydrates
could be expected to compete with growth of leaves and roots and thus
reduce the maximum growth rate (Chapin et al. 1990). Nevertheless,
carbohydrate storage is a very common phenomenon in the plant kingdom
and production of assimilatory starch occurs in chloroplasts of all leaf tissues.
Therefore, in this chapter we investigate the functional role of assimilatory
starch and its interaction with growth using a starchless mutant compared
with a wild type of Arabidopsis thaliana (Schulze et al. 1991).
It is not known if assimilatory starch competes with growth processes
because methods which perturb the formation of starch by altering the
environment generally also have direct effects on growth, and therefore the
data are only correlative in nature. For example, reduced light will reduce
assimilatory starch and growth, but one cannot distinguish whether or not
plants with or without starch formation have increased growth at high light.
This problem can only be investigated by using isogenic plants, which have a
single mutation in the enzymatic pathway of assimilatory starch formation.
Only then can one compare plants with and without the capacity of starch
formation under identical conditions of light or nutrition. Here we describe
experiments using mutants of Arabidopsis with no, or very diminished,
starch production in order to study the effect of assimilatory starch on plant
performance, and to test to what extent respiration and growth are affected
by the lack of starch formation (Schulze et al. 1991; Stitt and Schulze
1993). In this sense, genetics and molecular biology enable us to ask new
questions in ecophysiology about regulation of plant growth and its response
to environment.
for Growth in Arabidopsis thaliana Wild-Type
and Starchless Mutants
W. Schulze and E.-D. Schulze
6.1 Introduction
Vegetative growth is generally assumed to reach maximum rates when
plants invest as much carbohydrate as possible in the growth of new leaves
(Monsi and Murata 1970; Schulze 1983). Only with new leaves are additional
production organs established which by compound interest contribute to
further growth (Harper 1989; Diemer et al. 1992). Growth rates are eventually limited by supply of resources, such as water and nutrients, or light in
the case of self-shading (Schulze and Chapin 1987). Storage of carbohydrates
could be expected to compete with growth of leaves and roots and thus
reduce the maximum growth rate (Chapin et al. 1990). Nevertheless,
carbohydrate storage is a very common phenomenon in the plant kingdom
and production of assimilatory starch occurs in chloroplasts of all leaf tissues.
Therefore, in this chapter we investigate the functional role of assimilatory
starch and its interaction with growth using a starchless mutant compared
with a wild type of Arabidopsis thaliana (Schulze et al. 1991).
It is not known if assimilatory starch competes with growth processes
because methods which perturb the formation of starch by altering the
environment generally also have direct effects on growth, and therefore the
data are only correlative in nature. For example, reduced light will reduce
assimilatory starch and growth, but one cannot distinguish whether or not
plants with or without starch formation have increased growth at high light.
This problem can only be investigated by using isogenic plants, which have a
single mutation in the enzymatic pathway of assimilatory starch formation.
Only then can one compare plants with and without the capacity of starch
formation under identical conditions of light or nutrition. Here we describe
experiments using mutants of Arabidopsis with no, or very diminished,
starch production in order to study the effect of assimilatory starch on plant
performance, and to test to what extent respiration and growth are affected
by the lack of starch formation (Schulze et al. 1991; Stitt and Schulze
1993). In this sense, genetics and molecular biology enable us to ask new
questions in ecophysiology about regulation of plant growth and its response
to environment.