Flower power: Floral and resource manipulations reveal how and why reproductive trade‐offs occur for lowbush blueberry (Vaccinium angustifolium)

Abstract

Plant reproductive trade‐offs are thought to be caused by resource limitations or other constraints, but more empirical support for these hypotheses would be welcome. Additionally, quantitative characterization of these trade‐offs, as well as consideration of whether they are linear, could yield additional insights. We expanded our flower removal research on lowbush blueberry (Vaccinium angustifolium) to explore the nature of and causes of its reproductive trade‐offs. We used fertilization, defoliation, positionally biased flower removal, and multiple flower removal levels to discern why reproductive trade‐offs occur in this taxon and to plot these trade‐offs along two continuous axes. We found evidence through defoliation that vegetative mass per stem may trade off with reproductive effort in lowbush blueberry because the two traits compete for limited carbon. Also, several traits including ripe fruit production per reproductive node and fruit titratable acidity may be “sink‐limited”—they decline with increasing reproductive effort because average reproductive structure quality declines. We found no evidence that reproductive trade‐offs were caused by nitrogen limitation. Use of reproductive nodes remaining per stem as a measure of reproductive effort indicated steeper trade‐offs than use of the proportion of nodes remaining. For five of six traits, we found evidence that the trade‐off could be concave down or up instead of strictly linear. Synthesis. To date, studies have aimed primarily at identifying plant reproductive trade‐offs. However, understanding how and why these trade‐offs occur represent the exciting and necessary next steps for this line of inquiry.

Wild Blueberry Fruit Drop: A Consequence of Seed Set?

“…Blueberry maggot fly (Rhagoletis mendax Curran) [20], spotted wing drosophila (Drosophila suzukii Matsumura) [21] and mummy berry disease (Monilinia vaccinii-corymbosi (Reade)) [22] are causal agents of wild blueberry fruit drop. Nitrogen fertilizer can cause fruit drop by resulting in increased vegetative growth and competition for nutrients with reproductive tissue [23]. Frost conditions have the potential to cause fruit drop by resulting in the death of embryos [10].…”

“…High air temperatures and drought can affect plant resources and cause physiological stress (optimal threshold for wild blueberry synthesis photosynthesis is 25 • C [24]). High numbers of fruits per stem or fruit per unit leaf area may result in fruit drop [23,25], and it is hypothesized that plant resources, such as water and nutrients, may enhance fruit drop at high fruit densities. The endogenous effect of genotype or clone is most likely a major causal agent of fruit drop.…”

Reproductive Biology of Wild Blueberry (Vaccinium angustifolium Aiton)

“…Brown and McNeil [91] suggest that the natural fruit drop is part of a bet hedging life history strategy and that cranberries always produce more flowers than they will bring to maturity. This is a possible hypothesis that might explain the wild blueberry asymptotic model and the plasticity in shifting resource allocation from the reproductive tissue to the vegetative tissue supports this type of life history strategy [60,61].…”

Effect of environmental factors on size and fecundity of field populations ofImpatiens glandulifera

“…For all sites combined and the Cork site analysed separately, positive correlations were found between the number of reproductive units, plant height, leaf size and the number of side branches. Trade-offs between reproductive and vegetative growth are thought to be caused mainly by carbon limitation (Bajcz and Drummond 2017), but under favourable conditions, reproductive output is expected to increase with plant size in annual plants. When all sites are taken into account, correlations may have been caused by more or less favourable conditions at the sites, e.g.…”