Abstract:
Three distinct stages of flower cluster abscission were identified
prior to fertilization: flowers which did not begin development (stage
1), flowers which had begun development (stage II) and clusters which
had begun to form distinct nuts (stage III). Abscission of stages I
and II coincided with a rapid increase in leaf area. Abscission of
stage III coincided with the rapid increase in ovary growth.
A localized dominance effect appeared to occur among buds located
in close proximity. This became evident when multiple buds occurred
at the same node or when numerous buds were borne on catkin peduncles.
Both 'Ennis' and 'Barcelona' averaged over one nut cluster per node
when multiple flower clusters were borne on a catkin peduncle.
GA₃, 50 ppm, induced multiple budding at nodes. Developing
female flowers were inhibited from maturing and abscissed. Male
catkin development was also inhibited but to a lesser extent. Significantly
greater numbers of female flowers differentiated in August on
those branches treated the previous spring with GA₃. Nuts per cluster
was increased with daminozide (2000 ppm), however, daminozide, TIBA
(50 ppm) and boron (one pound actual boron per acre) reduced nut size.
Daminozide, boron and TIBA did not influence the percent set at any
treatment date. Ethephon (500 ppm), increased set. At all three
treatment dates it increased percent set. The May 30 application
increased set 18 percent above the control. There was no influence
on set the year after treatment as a result of any of the sprays.
