This article is the first one of a series aimed at determining the num
erous interaction configurations adopted by H(2)0 molecules in macromo
lecular systems, using infrared spectrometry. These configurations are
important for understanding the role of water in such systems, partic
ularly biosystems. This article concerns H2O molecules at low concentr
ation in an isolated plant cuticle. The analysis of quantitative varia
tions of the entire spectrum due to modifications of chosen parameters
such as stage of growth, humidity of the surrounding atmosphere, and
temperature shows that two types of interaction configurations exist f
or H2O molecules hydrogen bonded to surrounding molecules: There are '
'volatile'' molecules held by one hydrogen bond they formed with recep
tor sites of the cuticle and ''embedded'' molecules held by two strong
er or three hydrogen bonds which are part of the hydrogen bond network
of the cuticle. Embedded molecules do not evaporate, even at 100 degr
ees C. We emphasize the conditions which should be fulfilled in order
to extend such a method to other macromolecular systems.