Sequential decline in fruit resource allocation within inflorescences of Sagittaria trifolia: a test of non‐uniform pollination hypothesis

Abstract

Flowering plants often exhibit declining resource investment to floral organs, fruits and seeds temporally or spatially in an inflorescence. To account for such variances, non‐uniform pollination hypothesis, which highlights various mating environments each flower experiences, provides adaptive significance for allocation patterns but with controversial supports. Sagittaria trifolia (Alismataceae) was used to examine differences in seed number, seed weight and germination rate among sequential fruits within inflorescences. Ovule number was also investigated to evaluate allocation patterns in the floral stage. To test the non‐uniform pollination hypothesis, we used three polymorphic microsatellite loci of S. trifolia to estimate the seed outcrossing rate in proximal and distal fruits. The results showed that the seed number, average seed weight and seed germination rate of S. trifolia gradually decreased from proximal to distal fruits within inflorescences. The percent of decrease in seed number between two contiguous fruits was 14.68 ± 3.22%, which was much stronger than the percent of decrease in ovule number at 6.95 ± 1.60%. Both proximal and distal fruits within inflorescences had high outcrossing rates (81.5 ± 5.0%, proximal; 82.3 ± 6.9%, distal) and they did not differ significantly. Overall, there was an acropetal decline of resource allocation to fruits within inflorescences of S. trifolia. Allocation pattern to ovules was not a limiting factor for seed production. The lack of difference in outcrossing rate between proximal and distal fruits indicated that the allocation strategy was probably not caused by non‐uniform pollination, but more likely position effects.

Factors affecting fruit and seed production of Paeonia ostii “Feng Dan”, an economically important oil tree

“…Unlike fruit and seed production, individual seed weight exhibited little variation across the flowering sequence, which is in agreement with studies on Aquilegia Canadensis (Kliber & Eckert, 2004). In contrast, individual seed weight declines temporally within inflorescences or plants in Aconitum gymnandrum (Zhao, Meng, Fan, & Du, 2008) and Sagittaria trifolia (Dai et al, 2018). Interpreting variation in individual seed weight in P .…”

“…Fruits are not uniformly distributed within inflorescences or individuals (Diggle, 1995;Lee, 1988). Commonly, the components of female reproduction show a reduction from early-opening (basal) to late-opening (distal) flowers (Cao, Xie, Wu, & Yang, 2015;Dai, Li, Wang, & Liao, 2018;Diggle, 1995;Henneresse, Kaiser, Wesselingh, & Tyteca, 2019). Three alternative (but not mutually exclusive) hypotheses may explain these patterns: resource preemption, intrinsic decline in investment in distal structures (architectural effects) and non-uniform pollen deposition.…”

De novo transcriptome assembly using Illumina sequencing and development of EST-SSR markers in a monoecious herb Sagittaria trifolia Linn

“…The breeding system of S. trifolia is monoecious and reproduces both sexually by seeds and asexually via corms ( Qin, Li & Dai, 2015 ). During anthesis, female flowers in an inflorescence open within one to three days followed by the blooming of male flowers which takes between four to ten days ( Dai et al, 2018a ). It is a self-compatible species pollinated by insects such as solitary bees, honeybees, syrphid flies, and other dipterans ( Dai et al, 2018a ).…”

“…During anthesis, female flowers in an inflorescence open within one to three days followed by the blooming of male flowers which takes between four to ten days ( Dai et al, 2018a ). It is a self-compatible species pollinated by insects such as solitary bees, honeybees, syrphid flies, and other dipterans ( Dai et al, 2018a ). Achene fruits of S. trifolia ripen generally after three weeks of flowering.…”

“…Previous research work on S. trifolia has devoted much effort to the antimicrobial activity and chemical composition ( Yoshikawa et al, 1993 ; Yoshikawa et al, 1996 ; Zheng et al, 2006 ; Li et al, 2009 ), growth and reproductive success( Daimon, Miura & Tominaga, 2014 ), physiological and biochemical responses to diesel ( Zhang et al, 2015 ), the internode elongation ( Sasayama et al, 2016 ), resource allocation patterns within inflorescences ( Dai et al, 2018a ; Dai et al, 2018b ), germination characteristics ( Ozaki, Shimono & Tominaga, 2018 ), and biochemical, phytochemical, and mineral composition analyses ( Ahmed et al, 2019 ). Despite its medicinal and economic importance, there is limited information regarding the molecular basis of this species.…”