Cytohistochemical Analysis ofMalus domesticaBorkh. Seeds from Shedding and Nonshedding Fruits

A histological, cytochemical, and ultrastructural investigation of seeds of control (nonshedding) and shedding fruits ofMalus domesticaBorkh. showed differences in the pattern of nutrient distribution. The kind and amount of storage compounds in the two seeds also differed. Protein bodies and starch were abundant in the control seeds and nearly absent in the seeds of shedding fruit. In the latter, there was a great abundance of phenols that exhibited a specific distribution in different tissues of the chalazal region. A cuticle was present on the inner side of the inner integument of the seeds of both control and shedding fruits. This cuticle was interrupted in the chalaza and formed a pathway for nutrient translocation, what we termed the “window.” Cell wall changes observed in the chalazal window were probably associated with the different distribution pattern of storage compounds and with the control of nutrient routing. The delayed and variable development of the embryos of seeds in shed fruits may be related to both the altered pattern of storage substances and their translocation to the embryo.