THE PHYSIOLOGICAL SIGNIFICANCE OF RESPIRATORY META...
For studying the effects of various substances on abscission of the leaf petiole of Euonymus japonica Thunb.L.f.the petiole explant test described by Addicott et al.was used with some modifications made by us.The position of treatment of various substances is showed in Figure 1.The notable fact should be mentioned that explant test performed under similar conditions showed a considerable degree of variation due to the differences in age of material and in time.
The results of present investigations justify the following conclusions：
1.Application of the various metabolites related to hexose monophosphate pathway，such as glucuronic acid，galacturonic acid，galactose and arabinose，gave rise to the depression of abscission of the petiole explant obviously.
2.The longer abscission time is observed by application of IAA，tryptophan and ascorbic acid.The effect is somewhat proportional to the concentration applied.It suggests that the action of these substances may be due to the enhancement of the HMP pathway.
3.Treatment with sodium fluoride，iodoacetic acid and malonic acid，the well known EMP-TCA inhibitors，prevent abscission strongly.(https://www.daowen.com)
4.Treatment with sodium phosphate，presumably as a HMP inhibitor，accelerates abscission demonstrably.The interesting evidence shows that the galacturonic acid，IAA and ascorbic acid can overcome this acceleration of activity.
5.Together with these observations，wich constitute the available evidence，we have come to the conclusion that the abscission is closely related to the respiratory pathways.The predominance of EMP-TCA route accelerates the abscission process，while the prevalence of HMP pathway delays it.
Hsueh Y.L.，T.S.You AND Y.S.Zhu（Laboratory of Plant Physiology，Fu Tan University）
