(212) Gas Exchange and Antioxidant Properties of Two Spinach (Spinacia oleracea L.) Cultivars of Contrasting Morphology

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  • 1 1Xavier University of Louisiana, Department of Biology, New Orleans, LA, 70125
  • | 2 2New Mexico State University, Department of Entomology, Plant Pathology and Weed Science
  • | 3 3Loyola University of New Orleans, Department of Biology

'Knowledge of constitutive levels of gas exchange and antioxidant properties under unstressed conditions is critical for elucidating their potential roles in stress tolerance, planning cultural practices, and evaluating nutritional quality of vegetable crops. This greenhouse study reports gas exchange, photosystem II efficiency, and pigment and antioxidant profiles of two spinach cultivars [SpinaciaoleraceaL., cvs. Bloomsdale Long Standing (Bloomsdale) and Hybrid Tyee (Tyee)] with contrasting morphology. `Bloomsdale', the cultivar with more compact stature and larger leaves, had 47% greater photosynthesis (Pnet) than `Tyee'. Stomatal conductance (gs) and transpiration (E) were 94% and 46% greater in `Bloomsdale' than `Tyee', respectively. However, photosystem II efficiency (Fv'/Fm') was only 8% greater in `Bloomsdale' than `Tyee'. Instantaneous water use efficiency was similar in both cultivars. `Bloomsdale' had nonsignificantly greater concentrations of chlorophylls a and b, lutein, β-carotene and violaxanthin than `Tyee'. Both cultivars had similar, marginal α-tocopherol concentrations (<0.1 ng·g-1 FW). However, `Tyee' had a greater chlorophyll a:b ratio which, combined with lower gs and E, suggests a possible advantage for `Tyee' over `Bloomsdale' under relatively dry and high light conditions. Further studies must be conducted to compare nutritional quality of the two cultivars, based on constitutive levels of pigments and antioxidants. Greater gas exchange activity in `Bloomsdale' than `Tyee' appears to be due more to CO2 acquisition/metabolism than photosystem II efficiency or concentrations of pigments and antioxidants.

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