Micropylar exudates in Douglas fir - timing and volume of production

In Pseudotsuga menziesii, a secretion fills the micropylar canal about 7 we eks postpollination until fertilization. Micropylar volumes were measured a nd found to show variation. Dissection of the ovuliferous scales caused exc ess fluid to be exuded from the micropylar canal, forming a drop at the tip of the micropyle. This drop was collected, and its production quantified i n three trees. Volume and percentage of ovules with drops were greatest whe n the archegonia in the female gametophyte were at central cell and/or egg cell stage. The volume of exuded drops far exceeded that of the micropyle. Production of subsequent drops by the ovules further confirms that the flui d is actively produced upon dissection.