Do Steviol Glycosides Act Either as a Carbon Storage Pool or in Osmoregulation within Leaves of Stevia rebaudiana?

• Published in: Journal of natural products (Washington, D.C.) Vol. 81; no. 11; pp. 2357 - 2363
• Main Authors: deGuzman, Ria, Midmore, David J, Walsh, Kerry B
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society and American Society of Pharmacognosy 26.11.2018
• Subjects: Carbon - metabolism; Carbon Dioxide - metabolism; carbon dioxide enrichment; carbon sequestration; Diterpenes, Kaurane - metabolism; energy; Glucosides - metabolism; glycosides; leaves; Light; osmolality; Osmoregulation; photoperiod; Plant Leaves - metabolism; sap; starch; Stevia - metabolism; Stevia rebaudiana; steviol; stevioside; Water; water stress
• ISSN: 0163-3864; 1520-6025; 1520-6025
• DOI: 10.1021/acs.jnatprod.8b00196

Steviol glycosides (SG) (with stevioside and rebaudioside A predominating) are present in wild-type Stevia rebaudiana, at approximately 10% of dry weight (dw), prompting a consideration of the autoecological role played by these compounds in terms of energy (C) storage and/or osmoregulation. The leaf starch pool was observed to change diurnally with respect to the light cycle (from 3.29% to 0.73% of leaf dw between dusk and dawn) and also to increase under constant light treatment (from 1.53% to 6.25% of leaf dw), while SG pools were relatively constant (around 6% w/dw). A similar trend was observed during exposure to elevated CO2 (800 ppm), with starch increasing (from 10% to 15% of leaf dw), while SG pool size was constant (around 12% w/dw). For plants subject to increasing water stress over several days, an increase in leaf sap osmolality was observed in the leaves of a severely stressed group (from −1 MPa to −3 MPa, after 2 days of treatment), while stevioside and rebaudioside A leaf concentration was relatively constant (around 16% w/dw). These results are not consistent with a role for SG as either a short-term C store or osmoregulator in S. rebaudiana.