Effects of {alpha}-Hydroxysulphonate on Respiration of Mung Bean Root Tips

Hydroxysulphonate (-HPMS) was found to have an inhibitory effecton dark respiration of mung bean root tips. Inhibition was greatestin regions nearest the apex. The inhibition of root respirationby -HPMS was not due to an inhibition of glycolic acid oxidase.It is suggested that the action of -HPMS was probably on acetylCOA synthetase.     

Rhythmic Production of CO2 by Tropical Orchid Flowers

Circadian rhythm of CO₂ production was observed in some tropical orchid flowers. The tight bud showed relatively low respiration and no rhythmic changes. As soon as the flower opened, respiration increased and rhythmicity became apparent. The period for the rhythm was about 24 hours. Dark treatment and detachment dampened the amplitude of the rhythm without affecting the rhythmicity. In depollinated and pollinated flowers, the rhythmicity was less pronounced. Pollination and depollination appeared to stimulate respiration at the trough of the cycle. However, there was no significant difference in respiration per day between the untreated and treated flower. Both pollination and depollination hasten the senescence of orchid flowers.     

Partitioning of 14C-Assimilate Between Sources and Sinks in the Monopodial Orchid Aranda Tay Swee Eng

Aranda Tay Swee Eng, an orchid hybrid with monopodial growthhabit, has a highly integrated source-sink assimilate partitioningpattern. The current inflorescence receives assimilate frommany rather than a few leaves, the vegetative apical shoot competeswith the inflorescence for assimilate supply in the upper shoot,and the fully-expanded leaves themselves constitute a majorsink for assimilate. Implications of these findings for improvementof harvestable yield in monopodial orchids are discussed. Aranda Tay Swee Eng, monopodial orchids, assimilate partitioning, source-sink relationships