Conclusion
Here we characterize the mechanism behind the p-type response of ABA
dynamics exhibited by highly drought tolerant species under long term
drought. The use of rapid bench dehydration to assess ABA biosynthesis
revealed that ABA biosynthesis on dehydration is inhibited once plants
are drought stressed to Ψtlp. Continual conjugation of
ABA appears to drive a decline in ABA levels once biosynthesis is
inactivated. Future work is needed to assess the occurrence of the
p-type behaviour in a wider range of species of seed plants, including
in herbaceous species which usually die after a slight decrease in
Ψl below Ψtlp.