The effect of the plant growth retardant RSW0411 on assimilate distribution in evening primrose

The pattern of dry weight and carbon allocation was studied in the evening primrose crop Oenothera spp., from the commencement of flowering to maturity. Following ¹⁴CO₂ exposure, leaves were the main sources of assimilates with reproductive parts as the main sinks. A developmental pattern for evening primrose is described in which roots provide resources for stem growth. Subsequently the reproductive structures on the mainstem develop followed by the reproductive structures of the sidestems. The sidestems behave as independent physiological units until late in the season when they import assimilate from the mainstem leaves. The application of the plant growth regulator RSW0411 increased the weight of reproductive structures on the mainstem. The consequences of this for yield and agronomic practice are discussed.