Indole compounds in photoinduced plants 



Table 4 

 Stability of lAA in a series of buffers ranging from pH 1-5 to 9-Ot 



t Similar results were obtained when the experiments were done in the presence of plant tissue extracts in the 

 buffers. 



not kept for more than a few hours so that changes in the structure of lAA 

 would not be expected to occur. 



The influence of infra-red and fluorescent radiation on the stability of lAA 

 both in the presence and absence of plant brei is recorded in Table 5. 



Table 5 

 Influence of infra-red and fluorescent radiation on the stability of lAA in the presence and absence of 



soybean leaf tissue 



t Theoretical value for total recovery of lAA is 0-28 to 0-30. 



The results indicate that there is little or no inactivation of lAA as a result 

 of short-term exposures to either infra-red or flviorescent lighting. The 

 intensities used in these experiments are much higher than those which are 

 usually encountered under laboratory conditions. 



It is often necessary to inactivate the enzyme systems which are responsible 

 for catalysing the synthesis of lAA from tryptophan. Heating plant tissue 

 to destroy these enzymes was first proposed by Gustafson (1941), but later 

 discarded by other workers who found that boiling water released inhibitors 

 of auxin from the tissue (Terpstra, 1953). Since the Arena coleoptile test was 



61 



