Changes in oxalate composition and other nutritive traits in root tubers and shoots of sweet potato (Ipomoea batatas L. [Lam.]) under water stress

Abstract

BACKGROUND: The presence of insoluble calcium oxalate druse crystals (CaOx) in sweet potato (Ipomoea batatas) can negatively affect its nutritional quality. Photosynthesis, starch, and protein composition are linked with oxalate synthesis and tuber quality under water scarcity. Our main objective was the oxalate quantitation of sweet potato tubers and shoots and also to assess how drought changes their nutritional value. Eight sweet potato accessions from Madeira, the Canaries and Guinea-Bissau were analyzed for their response to drought stress. Tubers and shoots were analyzed for total (T-Ox), soluble (S-Ox) and insoluble (CaOx) oxalates, protein, chlorophyll content index (CCI), soluble starch, starch swelling power, and starch solubility in water. RESULTS: The S-Ox and CaOx content was higher in shoots. Six accessions were above maximum CaOx levels for raw consumption. Accessions with more favorable responses to drought had decreased CaOx with S-Ox increase content for osmoregulation.They also presented slightly decreased CCI and protein contents. These accessions also had an increased shoot starch content, for further tuber storage starch hydrolysis, and maintained the quality and functional properties of the tuber starch grain. Those with a less favorable response to drought had a higher T-Ox and CaOx content in both organs, hindering water absorption. They also had decreased protein and CCI, with a slight increase in tuber starch hydrolysis. CONCLUSION: Oxalate content was significantly related to carbohydrate metabolism, CCI, and protein synthesis. This study significantly contributed to the screening of the sweet potato stress response to drought, to adapt this crop to climatic change through breeding programs.

NIRS Estimation of Drought Stress on Chemical Quality Constituents of Taro (Colocasia esculenta L.) and Sweet Potato (Ipomoea batatas L.) Flours

“…It still allowed good photosynthesis activity and avoided the starch degradation into sugars, reducing its mobilization into tubers. However, in such conditions, the carbohydrate metabolism and photosynthesis oxidative processes can produce oxalic acid, forming insoluble salts when combined with free calcium, as CaOx insoluble druse crystals [61]. We observed that the whole-plant CaOx average content decreased in the first trial, with an increase in the second trial.…”

Abscisic acid phytohormone estimation in tubers and shoots of Ipomoea batatas subjected to long drought stress using competitive immunological assay

“…OA was quantitated in flour samples from root tubers and shoots (Gouveia et al 2020). Exactly 0.4 g of flour was extracted with hydrochloric acid (HCl, 6.0 M) to allow the reduction of oxalic into glyoxylic acid, with a further reduction into glycolic acid.…”

“…WUE reflects how plants manage the water use for vital activities and plant production during scarcity conditions, with the most tolerant ones usually displaying higher WUE (Mengel et al 2001, Ganança et al 2018, Gouveia et al 2019). The chlorophyll measured in the full‐grown leaves could be associated with the rate of photosynthesis, which is one of the most common parameters used as indicator of plant performance under drought stress (Shao et al 2015, Salehi‐Lisar and Bakhshayeshan‐Agdam 2016, Gouveia et al 2020). The carbon isotopic discrimination (Δ 13 C), that represents the photosynthetic depletion of 13 C in field‐grown plants, is linked with stomatal aperture and is commonly used in C3 plants for the assessment of drought resilience (Farquhar et al 1989, Zhang et al 2015, Gouveia et al 2019).…”

“…Oxalic acid (OA) is an ethanedioic acid that inhibits ABA‐induced stomatal closure in Arabidopsis thaliana plants (Guimarães and Stotz 2004). OA is a free acid that can form an equilibrium between soluble (potassium or sodium oxalate) or insoluble (calcium oxalate) salts, which variation plays an important role in the plant ion balance and osmoregulation under drought conditions (Franceschi and Horner 1980, Gouveia et al 2020).…”

“…The chlorophyll content index (CCI), Δ 13 C, OA and WUE traits were previously used in the evaluation of the crop resilience to water scarcity environments (Gouveia et al 2019, Gouveia et al 2020). To date, a few works reported the ABA effects on sweet potato cultivars, including tuber yield of two accessions grown in fully irrigated pots (Nakatani and Komeichi 1991), the inhibitory growth effects of exogenous application of ABA to in vitro plantlets of one accession (Jarret and Gawel 1991), sink activity through leaf‐petiole cuttings from one accession grown in a growth chamber and treated with ABA solution (Nagata and Saitou 2009), and growth of in vitro shoots of two accessions exposed to osmotic pressure induced by polyethylene glycol (Lau et al 2018).…”