Data for: Flowers that self-shade reduce heat stress and pollen limitation

Premise: Plants are facing increased risk of heat stress with global
climate change. Reproductive tissues are particularly sensitive which can
result in lower plant fitness. Floral shading and closure are possible
mechanisms to limit heat stress although most previous work on petal
orientation has considered adaptations to raise temperatures. We
hypothesized that floral shading could reduce temperature and increase
reproductive success. Results: Individual flowers of all four species that
shaded their pistils experienced temperatures 3 – 8 oC lower than those
that remained open and unshaded. In our wiring experiment, unencumbered R.
coulteri controls were 40% more likely to produce seeds than flowers that
were either permanently open or closed. Without added pollen, control
flowers produced 2x more seeds than flowers wired open and 8x more than
those wired closed. However, pollen addition eliminated the effects of
wiring and increased capsule weight and seed production. This suggests
that pollen limitation was responsible for observed differences in the
wiring treatments. Pollinators may prefer control flowers over those that
were wired open or closed; petal shading may make flowers cooler and more
attractive to pollinators. Conclusions: Petal shading may be a behavior
that allows flowers to reduce heat stress and increases their chances of
pollination and seed set.