Hyperhydricity-Related Morphologic and Biochemical Changes in Vanilla (Vanilla planifolia)

Shoot cultures of vanilla (Vanilla planifolia)
showed a progressive change toward hyperhydricity syndrome
(HHS) leading to the necrosis of shoot buds when
transferred to liquid medium of shake-flask type from solid
(gelled) medium (S). HHS was also associated with severe
damage at cellular and subcellular levels, an increase in
free polyamines (PAs) and accumulation of water, a
decrease in quantities of chlorophyll and protein, and
drastic changes in reducing and nonreducing sugars.
Spermine was by far the major polyamine in all the analyzed
cultures. The progression toward and onset of HHS
showed higher activities of antioxidant enzymes, indicative
of the shoots’ defensive efforts against oxidative stress.
The specific enzyme activities of normal and H2 stages
were 342.6 and 350.35 U mg-1 protein for peroxidase
(POD, EC 1.11.1.11), 38.4 and 30.38 U mg-1 protein for
superoxide dismutase (SOD, EC 1.15.1.1), and 71.3 and
82.75 U mg-1 protein for catalase (CAT, EC 1.11.1.6),
respectively. The kinetic parameters of the culture medium
suggested that nutrient utilization was normal in HHS and
that the severe biochemical alterations and cellular damage
were mainly due to oxidative stress.