Relationships between the contact coiling and endogenous growth regulators contents in cucumber tendrils were characterized as follows:
1. During the growth periods of tendrils, IAA content extracted were the highest, followed by tryptophan and IAAId. IAA content was particularly pronounced at the middle stage of tendril development, which corresponded to good contact coiling.
2. The quantity of IAA extracted was approximately twofold higher at the tip portion as compared with that at the basal portion. This suggested that IAA should be exclusively involved in contact coiling phenomena.
3. IAA extracted from non-contact coiling tendrils was 5.26 micrograms per gram fresh weight, but only 4.25 micrograms per gram fresh weight was extracted from contact coiling tendrils. There was no significant difference of IAAId and tryptophan contents.
4. IAA contents were the highest in tendrils sampled in August, followed by October and December samples.
5. IAA content was markedly higher when plants were grown at high temperatures as compared with those at low temperatures. Light intensities, however, had no effect on endogenous growth regulators contents.
6. Tendrils treated with IAA showed 100% contact coiling. But lower rate of contact coiling was (approximately 63%) noticed when IBA and NAA were used, and GA₃ failed to show any significant responses.
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