Determining Ion Toxicity in Cucumber under Salinity Stress

Cucumber (Cucumis sativus L.), an important vegetable crop, is sensitive to NaCl. Its salinity tolerance can be improved by grafting onto pumpkin rootstocks, which restricts the uptake of Na+, but not of Cl−. Although Na+ seems to be more toxic than Cl− in cucumber, tissue tolerance to Na+ and Cl− i...

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Bibliographic Details
Published inAgronomy (Basel) Vol. 10; no. 5; p. 677
Main Authors Chen, Tsu-Wei, Gomez Pineda, Ilka Mabell, Brand, Annika Marlen, Stützel, Hartmut
Format Journal Article
LanguageEnglish
Published Basel MDPI AG 01.05.2020
Subjects
Agricultural production
Conductance
Cultivars
Experiments
Genotypes
Grafting
Horticulture
Humidity
Hypotheses
Immunological tolerance
ion exclusion
ion recirculation
ion toxicity
Leaves
Osmolarity
Photosynthesis
Physiology
Resistance
Rootstocks
Salinity
Salinity effects
Salinity tolerance
Salt
salt stress
Seeds
Sodium
Sodium chloride
Stomata
Stomatal conductance
tissue tolerance
Toxicity
Netherlands
Germany
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Summary:Cucumber (Cucumis sativus L.), an important vegetable crop, is sensitive to NaCl. Its salinity tolerance can be improved by grafting onto pumpkin rootstocks, which restricts the uptake of Na+, but not of Cl−. Although Na+ seems to be more toxic than Cl− in cucumber, tissue tolerance to Na+ and Cl− is still unclear. In this study, a mixed-salt experiment, designed for equal osmolarity and equimolar concentrations of ions between treatments, was conducted using cucumber genotypes “Aramon” and “Line-759,” which are different in Na+ and Cl− exclusion. This combination of treatments generated various patterns of ion concentrations in leaves for deriving the response curves of photosynthesis and stomatal conductance to ion concentrations. In both cultivars, photosynthesis and stomatal conductance were sensitive to leaf Na+ concentration but insensitive to Cl− concentration. In these genotypes, tissue tolerance to Na+ varied independently of Na+ exclusion. Grafting “Aramon” onto pumpkin rootstock modified the Na+/Cl− ratio in leaves, reduced Na+ uptake, enhanced K+ transport towards the young leaves, and induced Cl− recirculation to the old leaves. These results suggest that (1) cucumber cannot restrict the Na+ accumulation in leaves but is able to avoid overaccumulation of Cl−, and (2) pumpkin rootstock regulates the recirculation of K+ and Cl−, but not Na+.
ISSN:2073-4395
2073-4395
DOI:10.3390/agronomy10050677