Variation of Chloroplast‐associated Processes with Divergent Selections from Zea mays L.1

Abstract

Associations among chloroplast characteristics were investigated using divergent selections from Zea mays L.; narrow (NL) vs. wide (WL) leaves, two replicates low (LP) vs. high (HP) stalk volume (sixth leaf stage) and golden (g) vs. normal (G) isopopulations. Leaf width selections differed in chlorophyll contents but had similar in vitro rates of ferricyanide reduction and noncyclic photophosphorylation, chloroplast protein levels and rates of net CO2 fixed per mg chlorophyll for three light intensities. The LP selections had inefficient photosynthetic systems relative to HP, while Golden had at least as efficient photosynthetic system as Normal. In contrast, LP selections had 13% and Golden 23% higher ferricyanide reduction and noncyclic photophosphorylation rates than HP and Normal, respectively. Information from in vitro measures was contradictory to that from other sources. Genetically controlled differences for chloroplast protein relative to chlorophyll level were found. Total chloroplast protein (TCP) and a fraction removed by NaOH (CPF) were both highly correlated with ferricyanide reduction rates. While TCP and CPF levels reflected seasonal effects, differences between genotypes for protein levels remained relatively consistent. TCP measure was proposed for population genetic studies to establish whether photochemical properties of chloroplasts have value as selection criteria.