Axiocam colour

H&E images were acquired using a Zeiss Axio Scan.Z1 equipped with an Axiocam colour CCD camera using the ZEN Blue software (all from Zeiss). Live cell images were acquired using a Nikon Eclipse Ti‐E microscope (Nikon). Immunofluorescence images of tissues were acquired using a Zeiss LSM 800 confocal microscope (Zeiss).

Relative embryo size (E:E ratio: ‘embryo to endosperm ratio’) was measured in both seed lots on arrival and during embryo growth experiments described below. In all cases, reported measurements were made on ten viable seeds that had been stained with TZ as described above. Embryos were extracted from the seed, and both the embryo and the endosperm were photographed using a camera (Carl Zeiss Axiocam Colour) mounted on a Stemi SV 11 Microscope (Carl Zeiss, Welwyn Garden City, UK). Embryo and endosperm lengths were measured from the photographs using the software Axiovision 3.1.2.1 (Carl Zeiss).
For testing embryo growth at different temperatures, the effect of nitrate and GA_3, and the effect of desiccation at different stages of embryo development, ten Petri dishes were sown for each treatment, each containing 15 seeds. Every 14 days, a Petri dish was randomly selected from each treatment and the E:E of ten viable seeds, randomly selected, was measured as described above.