Effects of CO2 enrichment and drought pretreatment on metabolite responses to water stress and subsequent rehydration using potato tubers from plants grown in sunlit SPAR chambers

Authors: Barnaby, Jinyoung; Fleisher, David; Baligar, Virupax; Reddy, Vangimalla; Sicher Jr, Richard

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2015
Publication Date: 10/30/2015
Publication URL: https://handle.nal.usda.gov/10113/63006
Citation: Barnaby, J.Y., Fleisher, D.H., Baligar, V.C., Reddy, V., Sicher Jr, R.C. 2015. Effects of CO2 enrichment and drought pretreatment on metabolite responses to water stress and subsequent rehydration using potato tubers from plants grown in sunlit SPAR chambers. Journal of Plant Physiology. 189:126-136.

Interpretive Summary: Potato plants are shallow rooted and are susceptible to water stress. In addition to reducing yields, water stress diminishes crop quality by causing clear areas that turn brown during cooking at high temperatures. Our study investigated the effects of drought and rehydration on soluble components in harvested potatoes. Results showed that carbon dioxide enrichment slightly decreased the effects of water stress on potato tubers but not to the extent that was observed for leaves. The most interesting observation here was that many drought related compounds accumulated in response to water stress but failed to revert to control levels two weeks after potato plants were fully rehydrated. This data was in contrast to published observations for structural plant tissues, such as roots, shoots and leaves, which indicated soluble sugars quickly reverted to control values after desiccated tissues were rehydrated. We postulated that potatoes, unlike leaves and structural roots, uniquely cannot re-export sugars that accumulated during drought. These results are of considerable interest to growers, breeders and extension specialists working with the potato crop.

Technical Abstract: Experiments were performed using naturally sunlit Soil–Plant–Atmosphere-Research chambers that provided ambient or elevated CO2. Potato plants were grown in pots that were water sufficient (W), water insufficient for 12 to 18 days during both vegetative and tuber development stages (VR), or water insufficient during tuber development (R). In the ambient CO2 treatment, a total of 17 and 20 out of 31 tuber metabolites differed when comparing the W to the R and VR treatments, respectively. Hexoses, raffinose, mannitol, branched chain amino acids, phenylalanine and proline increased and most organic acids remained unchanged or decreased in response to drought. Metabolite responses to drought during tuber initiation were mitigated by drought pretreatment. Rehydration and CO2 enrichment also mitigated some effects of drought on tuber metabolites. Specific osmolytes, including glucose, branched chain amino acids and proline, remained elevated following 2 weeks of rehydration in both the Amb and Elv CO2 treatments. Conversely, fructose, raffinose and some organic acids reverted to control levels upon rehydration. Failure of desiccated plant tissues to mobilize osmolytes after rehydration was unexpected and was likely because tubers function as terminal sinks.