Response of potato dry matter assimilation and partitioning to elevated CO2 at various stages of tuber initiation and growth

Abstract

Plants are able to adjust their development of sink organs in response to elevated atmospheric CO2, but there is an incomplete understanding of the processes responsible for alteration in sink capacity and carbon partitioning among alternative sinks. In potato (Solanum tuberosum L.), studies have shown that elevated CO2 increases partitioning to tubers. The objectives of the current studies were to elucidate growth response to elevated CO2 at discrete stages before and after imposition of tuber-inducing photoperiods, and test whether tuber sink development responds to elevated CO2 primarily by altering tuber initiation, cell proliferation or enhancement of tuber cell size. Contrary to the hypothesis that an initial phase of CO2 enrichment would have carry-over effects, plants pre-treated for four weeks with elevated CO2 before tuber initiation increased whole-plant biomass during tuber initiation to a similar extent as those receiving a control pretreatment, though partitioning was shifted toward stems. Elevated CO2, whether imposed before or after a tuber-inducing photoperiod, did not increase tuber number. Flow cytometry of tuber nuclei was used to determine cell numbers and nuclear DNA endoreduplication. Elevated CO2 imposed at both the initial two weeks after the start of tuber-inducing photoperiod and in the next two weeks of tuber bulking substantially increased tuber size by enhancing cell proliferation, not by increasing average cell volume or nuclear DNA size-class (endoreduplication). We conclude that the ability of tubers to stimulate cell proliferation throughout tuber initiation and tuber-bulking stages contributes to enhanced partitioning into tubers in elevated CO2 environments.