Physiological responses of quinoa (Chenopodium quinoa Willd.) to drought and waterlogging stresses: dry matter partitioning

Quinoa (Chenopodium quinoa Willd.) plants responded differently to drought and waterlogging. Plant and root dry weights (DW) were lower in both drought and waterlogging conditions than in well-watered conditions, but the lowest values were obtained under waterlogging. However, the root weight ratio (RWR: root dry weight per unit of plant dry weight) did not show significant changes in any treatments. Leaf area (LA) and specific leaf area (SLA) were higher in drought than in waterlogging, but drought and control treatments showed no significant differences. Conversely, specific leaf weight (SLW) and relative water content (RWC) were higher under waterlogging than drought. However, between control and waterlogging conditions, no a significant difference in RWC values emerged. In addition, the number of leaves and height of plants remained unchanged in all treatments. The lowest content of total chlorophyll, chlorophyll a and chlorophyll b was observed in waterlogging conditions while between control and drought treatments there were no significant differences. Chlorophyll a/b ratio remained unchanged in all treatments. Leaf nitrogen content, expressed per unit of leaf dry weight (N-m), was lower in control plants and remained unchanged under drought and waterlogging conditions. However, when it was expressed per unit of leaf area (N-a), waterlogging produced the highest value. In addition, soluble protein content was also higher in waterlogging than in control and drought conditions. Proline content was higher under drought than in control and waterlogging conditions; however, there was no a significant difference between control and waterlogging treatments. Between control and drought treatments there were no differences in starch, sucrose or fructose contents. Glucose and total soluble sugar contents were higher under drought than in well-watered conditions. However, the highest amounts of soluble sugars and starch were found in waterlogging. Relationships between soil water surplus and quinoa growth are discussed.