Sugarcane plants were grown for 10 months in the greenhouse at 27°, considered the optimal temperature,
and at low temperature (15°) and high temperature (45°). The growth pattern, biomass production,
sugar levels in leaves and stem, and activity of the enzymes involved in sucrose metabolism were determined
on plants grown at each temperature.
Plants maintained at 15° were very slow growing, with few and short internodes and few leaves. At 45"
the plants had nearly as many internodes and leaves as control plants (21), but the internodes were smaller
and shorter and the leaves became dry earlier; side shoot formation (tillering) was increased. The
shoot/root ratio was approximately constant over time and the same for all three growth temperatures.
The leaf area per plant increased over time and was highest at 27°. The leaf area per shoot biomass was
constant over time, but twice as high at 15° as at 45° and 2.5 higher than at 27". Total biomass production
was half to one third at 45° and one tenth at 15 0. The carbohydrate level in the leaves, especially sucrose
and starch, were highest in plants grown at 15° and lowest in plants grown at 45°. This result together
with the growth data was interpreted as indication that sucrose translocation by the phloem is especially
strongly inhibited at 15°, whereas at 45° the elevated leaf respiration, which is highest at 45°, reduces the
amount of available sugar for translocation.
The sucrose concentration in the stalk was the same in internodes for plants grown at 15° and 27° and
lower in internodes of plants grown at 45°. The hexose concentration in the young internodes was higher
at 27" than at the other temperatures, indicating the higher growth rate. All four enzymes of sucrose metabolism
(acid and neutral invertase, sucrose synthase and sucrose phosphate synthase) were highest in the
stalk at 27° and lowest at 15°; the development of activity during internode ripening was the same for all
three temperatures. There was a strong correlation, valid for all three growth temperatures, between the sucrose
concentration in the stalk internodes and the difference between sucrose phosphate synthase and
acid invertase, not however for neutral invertase, although the latter may be higher in activity in some
cases. The results are taken as evidence for a decisive role of acid invertase in regulation of sugar storage in
sugarcane.
Sugarcane plants were grown for 10 months in the greenhouse at 27°, considered the optimal temperature,
and at low temperature (15°) and high temperature (45°). The growth pattern, biomass production,
sugar levels in leaves and stem, and activity of the enzymes involved in sucrose metabolism were determined
on plants grown at each temperature.
Plants maintained at 15° were very slow growing, with few and short internodes and few leaves. At 45"
the plants had nearly as many internodes and leaves as control plants (21), but the internodes were smaller
and shorter and the leaves became dry earlier; side shoot formation (tillering) was increased. The
shoot/root ratio was approximately constant over time and the same for all three growth temperatures.
The leaf area per plant increased over time and was highest at 27°. The leaf area per shoot biomass was
constant over time, but twice as high at 15° as at 45° and 2.5 higher than at 27". Total biomass production
was half to one third at 45° and one tenth at 15 0. The carbohydrate level in the leaves, especially sucrose
and starch, were highest in plants grown at 15° and lowest in plants grown at 45°. This result together
with the growth data was interpreted as indication that sucrose translocation by the phloem is especially
strongly inhibited at 15°, whereas at 45° the elevated leaf respiration, which is highest at 45°, reduces the
amount of available sugar for translocation.
The sucrose concentration in the stalk was the same in internodes for plants grown at 15° and 27° and
lower in internodes of plants grown at 45°. The hexose concentration in the young internodes was higher
at 27" than at the other temperatures, indicating the higher growth rate. All four enzymes of sucrose metabolism
(acid and neutral invertase, sucrose synthase and sucrose phosphate synthase) were highest in the
stalk at 27° and lowest at 15°; the development of activity during internode ripening was the same for all
three temperatures. There was a strong correlation, valid for all three growth temperatures, between the sucrose
concentration in the stalk internodes and the difference between sucrose phosphate synthase and
acid invertase, not however for neutral invertase, although the latter may be higher in activity in some
cases. The results are taken as evidence for a decisive role of acid invertase in regulation of sugar storage in
sugarcane.
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