LEAF ANATOMY OF 2 LYCOPERSICON SPECIES WITH CONTRASTING GAS-EXCHANGE PROPERTIES

Lycopersicon pennellii (Cor.) D'Arcy possesses greater drought resista nce and higher water use efficiency (WUE) than the domesticated tomato L. esculentum Mill. A previous report suggested three restriction fra gment length polymorphism markers for whole plant WUE. This study iden tifies species differences in anatomical, biochemical, and physiologic al characteristics of leaves related to leaf gas exchange and whole pl ant WUE, which can later be tested with the molecular markers. Lycoper sicon pennellii exhibited 29% lower stomatal frequency, more even dist ribution of stomata between the upper and the lower leaf surfaces, and a 54% thicker leaf with 31% greater air space volume relative to tota l leaf tissue volume than L. esculentum. Trichomes were fewer, but lon ger, and the ratio of air exposed mesophyll surface area relative to e xternal leaf area was 41% greater for leaves of L. pennellii. However, this species contained 13% less chlorophyll and had 11% lower ribulos e-1,5-bisphosphate carboxylase/oxygenase (rubisco) activity per unit l eaf area than L. esculentum. The mean stomatal resistance (r(s)) was g reater and substantially less variable among leaves of L. pennellii, b ut those leaves of L. pennellii and L. esculentum that had the same r( s) also operated at the same photosynthesis rate (A) and WUE. Therefor e, differences in A and WUE among the two tomato species could be full y explained by contrasting stomatal properties. Either the differences in individual leaf anatomical, biochemical, and physiological charact eristics negated each other and did not substantially alter A and WUE, or the expression of the characters was linked to r(s) in the same wa y in both species.