Iodine Effects on Phenolic Metabolism in Lettuce Plants under Salt Stress

Abstract

Iodine, applied as iodate in biofortification programs (at doses of ≤80 μM), has been confirmed to improve the foliar biomass, antioxidant response, and accumulation of phenol compounds in lettuce plants. The changes in phenolic compounds induced by the iodate application appear to have functional consequences in the response of salt-stressed plants. Thus, the aim of the present study was to determine whether the application of iodate can improve the response of severe salinity stress and whether the resistance can be attributed to the phenolic metabolism in lettuce ( Lactuca sativa cv. Philipus), a glycophyte cultivated for food and consumed year round. In this work, the application of iodate, especially at 20 and 40 μM, in lettuce plants under salinity stress (100 mM NaCl) exerted a significantly positive effect on biomass and induced higher activity in the enzymes shikimate dehydrogenase and phenylalanine ammonia-lyase as well as the lower MW phenol-degrading enzyme polyphenol oxidase. This increased hydroxycinnamic acids and derivatives in addition to total phenols, which appear to act as protective compounds against salinity. This study reveals that in agricultural areas affected by this type of stress, the application of iodate may be an effective strategy, as it not only improves lettuce plant growth but also supplements the human diet with phenolic compounds and the trace element iodine.

Use of Iodine to Biofortify and Promote Growth and Stress Tolerance in Crops

“…The positive effect occurred even when applying low concentration (<40 μM) of KIO 3 , increasing the activity of enzymatic antioxidants, such as superoxide dismutase (SOD) and ascorbate peroxidase (APX), as well as that of non-enzymatic antioxidants such as glutathione (GSH) and ascorbic acid (AA) (Leyva et al, 2011). In a more recent study, they found an increase in the antioxidant response and a greater accumulation of total phenolic compounds using KIO 3 at concentrations of 20 and 40 μM (Blasco et al, 2013). …”

“…The use of iodine in the nutrient solution in concentrations from 10 −6 M (equivalent to 0.13 mg L −1 ) in soilless culture typically produces an increase in biomass in leafy vegetables, such as Chinese cabbage, spinach, and lettuce (Borst Pauwels, 1961; Whitehead, 1973; Weng et al, 2003, 2008c; Zhu et al, 2003; Dai et al, 2004b; Blasco et al, 2013). The iodine concentration can be increased to 10 −5 M (equivalent to 1.3 mg L −1 ), to produce biofortified leafy vegetables using I − , ${\text{IO}}_3^{-}$, or iodoacetic acid (CH 2 ICOOH − ; Weng et al, 2008c).…”

“…It has been reported that the application of iodine as ${\text{IO}}_3^{-}$ is favorable to that of I − , especially for the synthesis of antioxidant compounds (Leyva et al, 2011; Blasco et al, 2013), although in some species such as strawberry, clover, and perennial ryegrass, I − is more efficient than ${\text{IO}}_3^{-}$ (Whitehead, 1973; Li et al, 2016). In lettuce, KIO 3 applied to the soil at up to 7.5 kg ha −1 IO 3 is more effective than KI, as it gave a better result in terms of biofortification (50–100 μg I per 100 g FW) and does not affect biomass negatively.…”

A multilevel investigation to discover why Kandelia candel thrives in high salinity

“…Notably, increased antioxidants and phenols have been found in the plants that have been subjected to salt treatment (Blasco et al . ). However, whether phenols, especially flavonoids, anthocyanin and lignin play any role in salt tolerance of woody halophytes remains unclear.…”

Hyperspectral image applied to determine quality parameters in leafy vegetables

“…Blasco et al (2013) applied iodate (20 and 40 mM) in lettuce plants under salinity stress (100 mM NaCl) and observed an increase on biomass, higher activity of antioxidative enzymes and lower activity of polyphenol oxidase. Another strategy to reduce salinity effect on lettuce plants is priming treatments on seeds.…”