Pollinating Phaseolus coccineus Lam. with P. vulgaris L. (PC X PV) predetermines that seeds will abort by the time they reach 10 mm in seed length, while P. coccineus selfed (PC X PC) develop normally. The overall objective of this work was to determine the causes of failure of the PC X PV seeds to develop to maturity. To meet this objective, the project compared pre-abortion seed development of PC X PV with normal seed development in PC X PC in the following areas; developmental patterns, ('14)C-photoassimilate partitioning, endogenous plant growth substances, and light effects.
Pod diameter was the only parameter measured that exhibited a linear relationship with seed length for both crosses. Seed length will then estimate embryo development. When the two crosses were compared, PC X PV showed (1) slower seed development with respect to days after pollination, (2) reduced pod length, (3) a higher (pod length)/(no. of seeds per pod) ratio, (4) slower embryo development, and (5) increased volume of liquid endosperm.
Partitioning of ('14)C-photoassimilates into developing seeds was studied at three stages of embryo development. When expressed as sink strength (% dpm) or sink activity (% dpm/d.wt.) there were no differences in partitioning between the two types of seeds. If the embryo is analyzed separately, the sink activity of PC X PV embryo was higher. Abortion of PC X PV embryos appeared not to be caused by a lack of newly fixed photoassimilates.
The concentration of four plant growth substances was determined in the seed coat, embryo, and liquid endosperm of PC X PC and PC X PV. High levels of zeatin riboside and dihydrozeatin riboside and the relatively low levels of indole-3-acetic acid (IAA) and abscisic acid (ABA) in the PC X PC embryo suggest functions for these compounds in normal embryo development. The timing of elevated levels of IAA and ABA in PC X PV embryos suggest that imbalances of these compounds may function in regulating embryo abortion.
Pod abscision of PC X PV occurs after 5 days in winter compared to 16 to 20 days during the summer. Supplemental lighting in winter had no effect on PC X PV pod abscision. Shading of plants in summer, to equal light intensities of winter, did not effect PC X PV pod abscicion.
Dissertation completed at the University of Minnesota, 1982
Hoover, Emily E..
Regulation of Fruit Set of Phaseolus Crosses by Pollen Source and Environment.
Retrieved from the University of Minnesota Digital Conservancy,
Content distributed via the University of Minnesota's Digital Conservancy may be subject to additional license and use restrictions applied by the depositor.