Effects of manganese deficiency on the pattern of tillering and development of barley ( Hordeum vulgare c.v. Galleon)

Abstract

The effects severe, moderate or slight manganese (Mn) deficiency on tillering and development of Galleon barley were examined in field and growth-cabinet experiments. Manganese deficiency delayed maturity in both field and growth-cabinet experiments. In the field, Mn-deficient plants were still tillering when the plants in plots receiving Mn fertilizer had ceased tillering and their stems were elongating. In growth-cabinet experiments, plants with moderate or severe Mn deficiency did not reach the stem-elongation stage of development, and continued to tiller until they died. The pattern of tillering was altered by Mn deficiency. Moderate deficiency decreased the rate of tiller emergence without affecting the rate of leaf emergence on the main culm. Therefore, at early tillering, deficient plants had fewer tillers. Manganese deficiency extended the period of tillering, and after control plants ceased tillering and their stems began elongating, deficient plants continued to tiller, eventually reaching the number of tillers of the control plants. Moderate and severe Mn deficiency prevented stem elongation and reproduction and plants continued to tiller. Eventually, moderate Mn-deficient plants had produced significantly more tillers than control plants or slightly deficient plants. Severe Mn deficiency resulted in death of plants before any increased tiller production. Manganese status affected apical development. When moderately Mn-deficient plants had one tiller, the main stem apex was at the double-ridge stage, compared with four tillers on the control plants which were at the late double-ridge or triple-mound stage. When the number of tillers of the Mn-deficient plants had increased to that of the control plants, the apex of the main stem was dead (shrivelled and dry) in the deficient plants, while that of the controls was at the awn primordium stage. There was no difference in grain-yield of slightly Mn-deficient and control plants, even though early tillering had been depressed and shoot biomass at maturity was lower in the former. Although moderately Mn-deficient plants produced greater number of tillers than control plants, these tillers did not produce any heads.