Ovule Development Study

Will predicted higher seawater temperatures retard ovule development in the seagrass Zostera marina L?

Funded by Private Donations

Co-PI’s: and S. Wyllie-Echeverria and L. Vanvolkenburgh

Our recent field observations suggest high temperatures could affect ovule development in Z. marina if they occur soon after the fertilization period of anthesis. During the summers of 2005 and 2006, mean fruit/ovule ratios were computed at Picnic Cove in the San Juan Archipelago. Significantly lower ovule development occurred in 2006 compared to 2005. Lower fruit/ovule ratios in 2006 were due to extremely high levels of embryonic abortion (> 80%) at the early stage of development.

Because abnormally high temperatures (~30 C) were recorded during the time when fertilization was most likely taking place, we suspect this occurrence was the primary factor affecting development and the lower number of viable seed within spathes (the organ in which ovules are fertilized, fruits develop and from which mature seed is released). Temperature stress during the fertilization period of anthesis is shown to influence seed viability of agricultural crops. Thus, we believe that our observation of high embryonic abortion in the early development of Z. marina ovules in 2006 could be the result of exposure to high temperatures during this critical developmental stage.

In addition, recent studies have found that genetically diverse populations of Z. marina are buffered against the negative effects of “extreme warming events”; as it turns out “heat rigor” (a term coined by Setchell 1929) reduces the density and biomass of some genotypes but not others. This discovery was made first through field observation and experimental manipulation and secondly through land based mesocosm treatments. Our objective is to evaluate ovule development from three locations with different genetic structure and clonal diversity patterns as a response to three temperature treatments and would represent the first study of this kind with Z. marina.