Reduced Transport Capacity Research Articles

Reduction of Auxin Transport Capacity with Age and Internal Water Deficits in Cotton Petioles

Auxin transport was examined in leaf petioles taken from the upper, middle, and lower leaf canopy of large cotton plants. The ability of petioles to transport auxin decreased with age (position) of the leaves. Plant water deficit reduced transport regardless of age. These correlations support the view that reduced transport capacity of petioles plays a significant role in the induction of abscission of lower or older leaves during water deficits.

Aging of membrane transport mechanisms in the central nervous system—high affinity glutamic acid transport in rat cortical synaptosomes

The kinetics of the sodium dependence of high affinity glutamic acid transport has been studied in synaptosomes from two and thirty month old rats. The data were fitted to kinetic models, and the minimal model giving best fit was identified for each age group. This minimal best fit model was found to be identical for both young and aged animals. Although there had occurred no basic change with age in the mechanism by which carrier, sodium, and glutamate interact in the transport process, substantial quantitative changes were found to occur; these changes result in a reduced transport capacity in the aged animals. The rate equation for the best fit model was utilized to define and calculate certain parameters which were then used to quantitatively compare the transport mechanism in young and aged animals.