Nitrogen Supply Affects Photosynthesis and Photoprotective Attributes During Drought-Induced Senescence in Quinoa

Abstract

Drought during senescence has become more common in Mediterranean climates in recent years. Chenopodium quinoa Willd has been identified as tolerant to poor soil conditions and drought. Previous observations have found that sufficient nitrogen (N) supply mitigates yield losses under terminal drought conditions. However, there is no understanding of the mechanisms behind this effect. We hypothesized that N up-regulates both photosynthetic and photoprotective elements during drought-induced senescence, alleviating the negative impact of drought on yield. The role of N supply and terminal drought on photoprotection was tested using three Chilean quinoa genotypes from different climatic zones: Faro, UdeC9, and BO78. Plants were grown under high nitrogen (HN) or low nitrogen (LN) conditions and subjected to terminal drought at the onset of senescence. Photosynthetic and photochemical and non-photochemical processes were evaluated at both the onset of drought and after 15 days of drought conditions. N supplementation modified most of the physiological parameters related to photochemical dissipation of energy, photosynthesis, and yield in quinoa. In contrast, water restriction did not affect photosynthesis in quinoa, and its effect on yield was dependent on the genotype. A significant interaction N × G was observed in photosynthesis, relative water content, protein content, Fv/Fm, and chlorophylls. In general, Faro was able to maintain higher levels of these attributes under LN conditions than UdeC9 and BO78. In addition, the interacting effects of N × W regulated the level of most pigments in quinoa as well as the photoprotective induction of non-photochemical quenching (NPQ) during senescence. During terminal drought at LN conditions, Faro presented a larger NPQ induction under drought conditions than UdeC9 and BO78, which was supported by a larger zeaxanthin content and de-epoxidation state of the xanthophyll pool. Interestingly, BO78 did not induce NPQ in response to drought-induced senescence but instead enhanced the content of betacyanins. This response needs to be researched in future works. Finally, we observed that LN supply reduced the correlationship between the de-epoxidation state of the xanthophyll cycle and NPQ. This could be an indication that N supply not only compromised the capacity for photosynthetic performance in quinoa plants, but also affected the plasticity of thermal dissipation, restricting further changes during drought-induced senescence.

Nitrogen physiology of contrasting genotypes of Chenopodium quinoa Willd. (Amaranthaceae)

“…Three lowland genotypes: Faro (latitude 34.47° and longitude 71.83°), UdeC9 (latitude 35.73° and longitude 72.53°) and BO78 (latitude 38,51° and longitude 71,4) from different geographical and climatic areas of Chile, but with similar morphological and phenological (senescing timing) characteristics, were used in this work. It has been reported that Faro increment its NUE value when developed at LN 27 , and display an enhanced level of photoprotective attributes when grown at LN compared with UdeC9 and BO78 42 . Faro seeds were obtained from Cooperative Las Nieves, whereas UdeC9 and BO78 seeds were provided for the National Seed Bank collection at Vicuña, Chile (INIA-Intihuasi).…”

Analysis of the growth and morpho-physiological performance of three cultivars of Colombian quinoa grown under a greenhouse

“…Agreeing with BASCUÑÁN-GODOY et al (2018a), different varieties of quinoa can adapt to low contents of soil elements; however, some varieties express the best foliar development under conditions of nitrogen unavailability, since they find significant differences compared to Chilean varieties. These data agree with what was obtained, while BS presented the highest number of leaves structures during the entire production cycle compared to BJ and T.…”

Seed characterization and early nitrogen metabolism performance of seedlings from Altiplano and coastal ecotypes of Quinoa

“…Additionally, citrulline and spermidine levels were 2-fold higher in Socaire than in Faro seeds. All these high nitrogen content compounds were related to drought and salinity tolerance in quinoa [27,28].…”

“…The major difference in these aboveground measured parameters between landraces was the capacity of Socaire plants to maintain qL values under LN conditions. Considering that photosynthesis is the principal process that explains qL values in Quinoa [28], this response could be the basis of the different amount of leaf protein between landraces under LN conditions. It is known that LN supply (and other stress conditions) induces production of secondary metabolites, triggering protein degradation and increasing photorespiration [31].…”