Some photosynthetic properties of the chlorophyll containing
layers of the immature cereal pericarp are described.
The tissue was found to be capable of high rates of photosynthesis as determined by light dependent oxygen evolution. These
rates were, however, reduced when isolated pericarps were used.
The activity and kinetic properties of the enzyme phosphoenol
pyruvate carboxylase (EC 4.1.1. 31) were investigated in some detail.
In general enzyme activity followed chlorophyll content of the pericarp, although these results depended upon the exact conditions of
plant growth. The dependence of enzyme activity on phosphoenol
pyruvate and glucose 6 - phosphate concentration was investigated.
The kinetic properties of the barley pericarp enzyme were found to be
very similar to that from the maize leaf.
The pericarp was found to contain high concentrations of phenols.
These could be oxidised either in non-enzymic reactions by metal ions
or enzymically by polyphenol oxidase. Thus extraction and reaction
media were devised in which enzyme degradation by the products of
phenol oxidation was minimised.
The products of carbon dioxide fixation in isolated pericarps
were in part identified, and resembled those reported for plants
having the pathway. Further, the measured enzyme activities
correlated with those found in plants with this pathway. The
metabolic events leading to the synthesis of phosphoenol pyruvate