The effect of boron on tipburn and auxin activity in lettuce

Lettuce plants (Lactuca sativa L.) grown in a boron deficient nutrient medium developed tipburn. Their leaves showed no overall increased auxin activity compared with those of control plants until they were 66 days old, when boron deficient plants showed a relative increase in the activity of one auxin. It is postulated that tipburn in lettuce may be caused by interacting factors including calcium and boron deficiences, and the ontogenetic age of the plant. Environmental and cultivar effects on the incidence of tipburn indicate that agronomic or genetic control measures may become feasible, if the mechanism controlling its expression can be further elucidated.