Photoassimilate Partitioning by Tillers and Individual Tiller Leaves in Field‐Grown Spring Barley

Abstract

A large proportion of initiated tillers on field‐grown barley (Hordeum vulgare L.) plants does not survive to bear grain. Increasing the percentage of tillers that survive has been hypothesized as an approach for increasing yield. The objective of this study was to determine photoassimilate translocation patterns of surviving and nonsurviving tillers in barley and to begin assessing the consequences of premature tiller senescence on grain yield. Field experiments were conducted in 1983 and 1984 at St. Paul, MN, on a Waukegan silt loam soil (Typic Hapludoll) using a replicated, randomized complete block design. Entire shoots, as well as individual tiller leaves, were labeled with 14CO2 in separate experiments. Following a 24‐h translocation period, the three genotypes evaluated did not differ in their fundamental tiller photoassimilate partitioning patterns. Nonsurviving tillers allocated proportionately more photoassimilate to the main shoot than surviving tillers, with the main shoot stem and emerging leaves receiving most of the photoassimilate. After onset of stem elongation, surviving tillers translocated proportionately less photoassimilate to the main shoot. During this time, the tiller stem received most of the photoassimilate fixed by a surviving tiller. From these experiments, we conclude that tillers, and especially nonsurviving tillers, may contribute appreciable quantities of current photoassimilate to the main shoot during early stem elongation, a factor that should be considered in assessing the agronomic value of tillers in barley.