Relationships Between Respiration During Imbibition
and Subsequent Growth Rates in Germinating Seeds
L. W. WOODSTOCK
With 3 Figures
Abstract
Differences in the respiration of germinating seeds precede differences in
seedling growth. Seeds which germinate rapidly and produce vigorously growing
seedlings have higher respiratory rates and lower respiratory quotients than nonvigorous seeds. Vigorous and non-vigorous seeds can sometimes be distinguished
within 1 hr after the start of imbibition by differences in respiration. The following germination-inhibiting treatments affect respiration during the first 6 hrs of
germination: Unfavorable long-term storage conditions in corn and barley;
freezing injury and heat damage in corn; chilling injury in lima beans; desiccation
treatments in sorghum; and gamma-irradiation in corn, sorghum, wheat and
radish. Measurements of respiration and growth of individual undamaged and
highly vigorous corn seeds revealed significant positive correlations between
respiratory rates and seedling growth. The results suggest that seedling growth
during the first few days of germination depends more on the overall level of
metabolic activity than on the activity of particular enzymes. Several possible
interpretations of the data are discussed.
Introduction
The question may be asked whether growth is usually controlled by a
single limiting reaction or whether it depends on the generallevel of metabolic activity. Even so "simple" an organism as E. coli is estimated to
contain between 2000-3000 different kinds of enzymes [14]. Because of
the large number of feedback control mechanisms and the speed of enzyme
synthesis, as soon as any particular enzymatic reaction becomes limiting,
processes may come into play which speed up that reaction. When this
happens, some other enzyme or compound becomes limiting and growth
may represent a kaleidoscopic series of "little crises" wherein one enzyme
or compound after another becomes limiting in rapid succession. With
sufficient metabolic adaptiveness to repair deficiencies as they occur, limitations in particular enzymes will be too transient to measure, and the
overall level of metabolic activity will be seen as limiting for growth.
Under such circumstances, a positive correlation would be expected between some measure of this activity and the growth rates.
and Subsequent Growth Rates in Germinating Seeds
L. W. WOODSTOCK
With 3 Figures
Abstract
Differences in the respiration of germinating seeds precede differences in
seedling growth. Seeds which germinate rapidly and produce vigorously growing
seedlings have higher respiratory rates and lower respiratory quotients than nonvigorous seeds. Vigorous and non-vigorous seeds can sometimes be distinguished
within 1 hr after the start of imbibition by differences in respiration. The following germination-inhibiting treatments affect respiration during the first 6 hrs of
germination: Unfavorable long-term storage conditions in corn and barley;
freezing injury and heat damage in corn; chilling injury in lima beans; desiccation
treatments in sorghum; and gamma-irradiation in corn, sorghum, wheat and
radish. Measurements of respiration and growth of individual undamaged and
highly vigorous corn seeds revealed significant positive correlations between
respiratory rates and seedling growth. The results suggest that seedling growth
during the first few days of germination depends more on the overall level of
metabolic activity than on the activity of particular enzymes. Several possible
interpretations of the data are discussed.
Introduction
The question may be asked whether growth is usually controlled by a
single limiting reaction or whether it depends on the generallevel of metabolic activity. Even so "simple" an organism as E. coli is estimated to
contain between 2000-3000 different kinds of enzymes [14]. Because of
the large number of feedback control mechanisms and the speed of enzyme
synthesis, as soon as any particular enzymatic reaction becomes limiting,
processes may come into play which speed up that reaction. When this
happens, some other enzyme or compound becomes limiting and growth
may represent a kaleidoscopic series of "little crises" wherein one enzyme
or compound after another becomes limiting in rapid succession. With
sufficient metabolic adaptiveness to repair deficiencies as they occur, limitations in particular enzymes will be too transient to measure, and the
overall level of metabolic activity will be seen as limiting for growth.
Under such circumstances, a positive correlation would be expected between some measure of this activity and the growth rates.