Protein body digestion in Polygonum pensylvanicum embryos during prechilling

The protein reserves of several seeds are stored in prominent spherical organelles called protein bodies. These organelles contain protein and phytin reserves (Matile 1968); they also contain several hydrolytic enzymes (ribonuclease, proteinase, and lypolytic enzymes) (Harris & Chrispeels 1975; Chrispeels et al 1976; Baumgartner et al. 1978; Chappel et al. 1980; Van der Wilden et al. 1980; Herman et al. 1981). During prechilling, protein body digestion has been associated with the decline in dormancy of seeds (Rost 1972; Villiers 1980, Jordan et al. 1982). Although protein body digestion is important for decreased dormancy and increased germination, no reports could be located concerning protein body digestion in different cell layers of a seed during prechilling. Therefore, two distinct, yet adjacent, cell layers in embryos from Polygonum pensylvanicum L. were studied using a transmission electron microscope (TEM) before and after the achenes (one-seeded indehiscent fruit) had been prechilled for 30 weeks. Mature Polygonum pensylvanicum achenes were collected at four maize fields in Iowa by placing aluminum screens below the plants and later removing the achenes from the screens. Four random samples of 100 achenes from each site were used to determine percentage moisture before prechilling tests were conducted; moisture percentage was also measured after prechilling. To measure percentage moisture, achenes were weighed before and after drying in a 105°C forced-air oven for 3 hrs.