SEED COAT INTEGRITY IN RELATION TO LEAKAGE IN ONION (ALLIUM-CEPA L) AND LEEK (ALLIUM-PORRUM L)

Intact seed coats may present a physical and/or chemical barrier to th e diffusion of compounds during germination. A positive relationship w as found between the number of seed coat cracks in leek and onion and optical absorbance of leachate reacted with ninhydrin. Scanning electr on microscopy revealed that non-leaking seeds generally had intact see d coats free from defects, while leaking seeds had seed coat cracks. L anthanum, a marker for solute movement, was found to diffuse through s eed coat cracks into the endosperm, while it was not readily taken up into intact seeds. In conclusion, seed coat cracks enhanced both solut e uptake and leakage compared with seeds with intact seed coats. Howev er, intact seed coats were not impermeable, and amino acids would even tually leak from non-germinable seeds. In practice, leakage tests have been used as a rapid method to assess seed quality. Our findings indi cate that results from leakage tests may be confounded by seed coat cr acks that influence leakage rates.