Abstract:
The objective of this work was to study the responses of two baby lettuce (Lactuca sativa
L.) cultivars, namely, green Paris Island and red Sanguine, to different NaCl
concentrations (0, 5, 10, and 20 mM). The study was conducted in a floating system and
plants were harvested at the stage of 5-6 leaves, outside leaf 6-10 cm in length (25 and 31
days after sowing for green and red lettuce, respectively). Photosynthetic parameters
(photosynthesis rate, stomatal conductance, transpiration rate, and intercellular CO2
concentration) and yield (leaf fresh weight) as well as color [L* (lightness), C*
(saturation), Hº (object’s color)], pigments (Chla, Chlb, total chlorophyll, carotenoids and
anthocyanins) and quality indices (appearance, freshness, taste and texture) were
determined. The results indicated that, in both cultivars, leaf fresh weight was reduced at
20 mM NaCl; the reduction depended on the limited water accessibility and
photosynthetic rate was suppressed in high salt concentration through stomatal
limitations aiming at the retention of water but resulting in restricted availability of CO2
.
Nevertheless, no limitations were observed in photosynthetic pigments and, thus, stomatal
closure was the dominant factor limiting photosynthesis. On the other hand, salinity
improved anthocyanin content and coloration in red lettuce and enhanced freshness in
green lettuce.
Keywords: Gas exchange, Leafy vegetables, NaCl, Plant growth, Sensory quality.
