The hypothesis that endogenously-produced nitric oxide (NO') gas is a natural plant growth regulator was experimentally
tested. Experimentation encompassed a wide spectrum of both climacteric and non-climacteric varieties of fruits,
flowers, vegetables and legume sprout species. Specific NO' probe monitoring of both vegetative and generative plant organs
revealed that temporal progress of maturation and senescence goes hand in hand with a significant decrease of NO' emission.
Conversely, exogenous application of the gas either by direct fumigation in an 0z-free atmosphere or by means of NO' releasing
biochemicals such as N-tert-butyl-a-phenylnitrone and 3 morpholinosyl-nonimine, markedly delayed senescence and maturation.
NO' decrease was moreover stoichiometrically related to ethylene upsurge, this phenomenon also being geared to ethylene
increment under short-term heat stress. Furthermore, a classic foliage expansion bioassay indicated a concentration-dependent
growth effect evidenced as a typical growth regulator-like response where low concentrations promote, and high concentrations
inhibit growth. Regarded together, experimental data lends support to the possible role of NO' as a natural senescence-delaying
plant growth regulating agent acting primarily, but not solely, by down regulating ethylene emission. © Elsevier, Paris