Developmental and Structural Section
Mikesell, Jan .
Seed mass variability and significances.
Objectives of this study were 4-fold: 1) to present phylogenetic trends, 2) to explain reversion to the mean in successive generations, 3) to correlate relative growth rate (RGR) with phenotypic traits, and 4) to explain several long-standing paradoxes. Paradoxes included: 1) how can seed mass variability within individual plants exceed variability within a species, 2) how can heavier seeds have a reduced RGR, but produce larger seedlings, and 3) how can seed mass be considered highly constant since seed mass variability is frequently exhibited. Quotient values calculated from heavier seeds ÷ lighter seeds manifested phylogenetic trends. The use of quotient values was an attempt to alleviate different techniques of ascertaining seed mass; e.g. use of pooled seeds, seed sieves, and weighing seed reserves. Mass ratios revealed larger quotients for angiosperms over gymnosperms (2.49 and 1.69, respectively), dicots over monocots (2.60 and 1.98, respectively), biennials over annuals (4.29 and 2.04, respectively) and advanced taxa over more primitive taxa (Scrophulariales = 6.57 and Loasales = 1.49). Large quotient values did not necessarily correlate to larger seed mass, as representatives of scrophs were small-seeded while members of the Loasales were large-seeded. Research with Pharbitis revealed a reversion to the mean with regard to average seed mass over successive generations; e.g. plants derived from seeds deviating in mass by 160 % ultimately produced the next seed generation varying in mass by less than 1 %.
1 - Gettysburg College, Biology, Box 392, North Washington Street, Gettysburg, Pennsylvania, 17325-1484, USA
Presentation Type: Paper
Location: Alpine A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 1:15 PM