Air drying method using nitrous oxide for chromosome counting in maize.

Nitrous oxide (N2O), colchicine, trifluralin, amiprophos-methyl, 8-hydroxyquinoline, and temperature pretreatments (cold and cold-hot-cold) were compared for chromosome counting in maize (Zea mays L.). Pretreated root tips were prepared by enzymatic maceration and air drying, and the number of countable figures and mitotic indexes were recorded. N2O treatment at 10 atm for 3 hr produced the largest number of countable chromosome figures (266.5 per preparation) and an average of 44.2 nonoverlapped chromosome figures per preparation. Treatment with 0.04% 8-hydroxyquinoline for 3 hr exhibited a moderate number of countable chromosome figures (53.9 per preparation). The effects of colchicine, trifluralin, amiprophos-methyl and temperature pretreatments were limited.