Micropylar exudates in Douglas fir – timing and volume of production

Abstract

 In Pseudotsuga menziesii, a secretion fills the micropylar canal about 7 weeks postpollination until fertilization. Micropylar volumes were measured and found to show variation. Dissection of the ovuliferous scales caused excess 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 in three trees. Volume and percentage of ovules with drops were greatest when 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 fluid is actively produced upon dissection