Variation in first callose plug position in seven tomato species. (A) Average length of the first interval in two independent experiments (black and white bars). An unpaired t test was performed between two independent experiments. Error bars are SEM, P< 0.5. (B) Distribution of first interval lengths. 150μm was used as a criterion to group first interval lengths. The percentages represent the proportion of pollen tubes with the first interval <150μm. S.hab: S. habrochaites; S.pen: S. pennellii; S.sit: S. sitiens; S.per: S. peruvianum; S.chi: S. chilense; S.pim: S. pimpinellifolium; S.lyc: S. lycopersicum.