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

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.

Microencapsulated betacyanin from colored organic quinoa (Chenopodium quinoa Willd.): optimization, physicochemical characterization and accelerated storage stability.

BACKGROUND: Betalains are presently gaining popularity as pigments for use as natural colorants and/or bioactive compounds in functional foods. Quinoa (Chenopodium quinoa Willd.) has been recognized as an extremely nutritious grain and has recently been found to be a novel and good betalain source. Microencapsulation has been studied as a protected-delivery procedure to stabilize betalains. There are no studies about microencapsulation of betacyanins extracted from quinoa using spray-drying technology. RESULTS: Optimal microencapsulation was obtained at a drying temperature of 165 °C, a rotameter air flow rate of 47 mm (940 L h-1 ) and 10% w/w maltodextrin, which produced good encapsulation yield (58.1%) and efficiency (100%). Optimized maltodextrin-betacyanin microcapsules (diameter 4.4 µm) have low moisture (1.64 ± 0.08%) and water activity (0.127 ± 0.006), a betacyanin content of 0.1995 ± 0.0017 g kg-1 and saponin content <0.080 mg kg-1 . The oxygen consumption rate by betacyanin was -4.373 × 10-5 bar min-1 at 80 °C and -6.67 × 10-5 bar min-1 at 90 °C, which was accompanied by fading of the color. CONCLUSION: Microencapsulated betacyanin was optimized by response surface methodology, and its stability was measured under accelerated conditions by oxygen consumption. Microencapsulations contain betacyanin and low saponin concentration, which might confer unique health-promoting properties. © 2018 Society of Chemical Industry.

Pigment production and growth of Alternanthera plants cultured in vitro in the presence of tyrosine

The aim of the present study was to investigate the influence of tyrosine on the in vitro growth and the production of the betacyanin pigment in Alternanthera philoxeroides and A. tenella. Nodal segments were inoculated in MS medium containing different concentrations of tyrosine (0, 25, 50 and 75 μM), and the number of sprouts and buds, height, root length, fresh matter of shoots and roots and betacyanin content were evaluated. In A. philoxeroides , the highest production of betacyanin (51.30 mg 100 g-1 FM) was in the stems with the addition of approximately 45 μM tyrosine, while the increase in the leaves was proportional to the tyrosine concentration, and the best average was obtained with a tyrosine concentration of 75 μM (15.32 mg 100 g-1 FM). Higher tyrosine concentrations were deleterious to the growth of A. tenella plants, and a concentration of 75 μM was considered toxic. However, a tyrosine concentration of 50 μM benefitted betacyanin production, which reached 36.5 mg 100 g-1 FM in the plant shoots. These results showed the positive effect of tyrosine on the production of betacyanin in both species; however, application at high concentrations hampered the growth of Alternanthera plants.