Abstract
Potato is adapted to cool environments, and there is concern that its performance may be diminished considerably due to global warming and more frequent episodes of heat stress. Our objectives were to determine the response of potato plants to elevated CO2 (700 μmol/mol) and high temperature (35/25 °C) at tuber initiation and tuber bulking, and to elucidate effects on sink developmental processes. Potato plants were grown in controlled environments with treatments at: Tuber initiation (TI), during the first two weeks after initiating short-day photoperiods, and Tuber bulking (TB). At TI, and 25 °C, elevated CO2 increased tuber growth rate, while leaves and stems were not affected. Whole-plant dry matter accumulation rate, was inhibited by high temperature about twice as much at TI than at TB. Elevated CO2 partially ameliorated high temperature inhibition of sink organs. At TI, with 25 °C, elevated CO2 primarily affected tuber cell proliferation. In contrast, tuber cell volume and endoreduplication were unaffected. These findings indicate that the TI stage and cell division is particularly responsive to elevated CO2 and high temperature stress, supporting the view that attention should be paid to the timing of high-temperature stress episodes with respect to this stage.
Highlights
Atmospheric CO2 levels and average global temperature have risen in the last decades and earth air temperature is predicted to continue to increase as a result of the rise in the levels of CO2 and other greenhouse gases [1,2]
Consistent with this, the current study indicated that elevated CO2 at 25 ◦ C during tuber initiation increased tuber dry matter accumulation rate (DMAR) by more than 60%, while leaf and stem DMAR was not significantly (p ≤ 0.05) affected, even though these organs collectively represented almost two thirds of the sink-organ DMAR (Figure 1)
At the tuber bulking phase, when most of plant photosynthate is used for starch storage in tubers, leaves had very low DMAR and stems had a net loss in dry matter, so almost all the benefit from elevated CO2 was obtained by tubers
Summary
Atmospheric CO2 levels and average global temperature have risen in the last decades and earth air temperature is predicted to continue to increase as a result of the rise in the levels of CO2 and other greenhouse gases [1,2]. Climate predictions indicate that accompanying an increase in global average temperatures of 1.5 ◦ C, will be a sharp rise in the likelihood of extreme heat stress events [6]. Altered rates of photosynthate availability can modify partitioning of photosynthate among plant parts, which in turn can have feedback effects on photosynthesis [10,11,12]. These effects may lessen the potential benefit of elevated CO2 on potato photosynthesis, as has been found in season-long free air CO2 enrichment (FACE) [11,13,14]. In potato, elevated CO2 can lead to greater stimulation of tuber development than above-ground plant parts such that harvest index is increased [15]
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