Physicochemical properties of culms in rye (Secale cereale L.) with a brittle stem

Abstract

In carrying out a genetic analysis of rye in terms of a “brittle stem” trait, sister plants with normal and brittle stems were obtained. The culms of plants were studied in terms of chemical composition, spectroscopic parameters, and mechanical strength. Differences among plants with different types of culm were found in terms of a number of indicators, such as the content of aromatic monomers of lignin and the ratio of different types of chemical bonds. Culms of normal and brittle rye of the same diameter vary in terms of an elastic modulus and elastic deformation limit. It was found that stems of mutant plants are destroyed under lateral stress by means of the fragile fracture mechanism, while those in normal plants are destroyed by ductile fracture. The limits of elastic deformation and strength are significantly higher for normal plants. By nuclear magnetic resonance methods, we detected differences in the chemical structure of lignins in terms of the following: the content of aldehyde and methoxyl groups, total aromaticity, and the number of ordinary ether bonds, by which lignin units are associated with polysaccharide fragments of cellular walls. Higher lignin content in a mutant does not increase the mechanical strength of the culm. On the contrary, there is a decrease in the limits of elastic deformation and an increase in the fragility of the shoots. Probably, the mutation bs, except for direct action (brittleness of the culm), causes an imbalance of metabolic processes in the formation of secondary cell walls and leads to deviations from the optimal ratio of carbohydrate and lignin components. The differences found in various indicators can be used in breeding research associated with important economic traits of cereal stems.