Effect of Light and Water Supply on Morphological and Physiological Leaf Traits of Red Beet.

Water and light are two important resources for red beet (Beta vulgaris var. conditiva Alef.) survival, growth and yield. Changes in leaf traits can be regarded as indicators for detection of crop responses to environmental stress, and could be utilized to select genotypes suitable for stressed environments. The objectives of the current study were to explore the adaptive changes of morphological and physiological leaf traits of red beet to water and light stress, and identify traits as potential suitable selection indicators in breeding programs. Red beet was treated with RED (red/far red ratio (R/FR): 1.29; transmitted photosynthetically active radiation (PAR): 66.9%), GREEN (R/FR: 0.43; PAR: 25.8%) photo-selective films, and with two water conditions i.e., 50% of water holding capacity (WHC) (W50) and 30% of WHC (W30). Plants subjected to GREEN had higher specific leaf area (SLA) (248.6 cm2 g−1) and leaf area ratio (LAR) (232.2 cm2 g−1) and lower soil-plant analysis development (SPAD) and water index (WI) (1.076) values. Water stress reduced leaf area index (LAI) by 39 and 59% (W50 and W30, respectively), normalized difference vegetation index (NDVI), green normalized difference vegetation index (GNDVI), and leaf zinc accumulation. Conversely, water shortage enhanced SLA, leaf mass ratio (LMR) (0.786 and 0.761 g g−1 for W50 and W30, respectively) and chlorophyll concentration. Red beet showed a strong plasticity under unfavorable growth conditions. Principal component analysis (PCA) indicated that suitable selection indicators of early adaptive changes were LMR, WI for drought and SLA, LAR for modification of PAR transmittance.