POLYGALACTURONASE IN TREE POLLENS

The pollens from 38 species of trees were analysed for polygalacturonase activity. All of the pollens contained polygalacturonase but the range of activities was great. Eastern cottonwood pollen contained the most polygalacturonase, with level about 12 times higher than that usually found in ripe tomato fruit, which has been the highest known plant source of this enzyme. Pollens from other members of Populus were generally high in polygalacturonase although some were relatively low. Pollens from the oak family contained high activity, with the largest amount in white oak pollen. Pollens from pecan, willows, birch and hickories contained moderate levels of polygalacturonase. The smallest activities were found in pollens from beech, sycamore and conifers. The polygalacturonases from eastern cottonwood and white oak pollens were partially purified and characterized. Both enzymes were found to be exo-polygalacturonases that require Ca2+ for activity, but they possessed different M(r)s, indicating that they are not identical. Exopolygalacturonase may be involved in some function related to pollination, but an explanation for the wide range of activities in different pollens is not obvious.