Fruit production in cranberry (Ericaceae: Vaccinium macrocarpon): a bet‐hedging strategy to optimize reproductive effort

Abstract

In the cultivated cranberry (Vaccinium macrocarpon), reproductive stems produce 1-3 fruit even though they usually have 5-7 flowers in the spring. We undertook experiments to test the hypothesis that this was an adaptive life history strategy associated with reproductive effort rather than simply the result of insufficient pollination. We compared fruit production on naturally pollinated plants with those that were either manually pollinated or that were caged to exclude insects. Clearly, insects are necessary for the effective pollination of cranberry plants, but hand pollination of all flowers did not result in an increase in fruit number. Most of the upper flowers, which had significantly fewer ovules than did the lower flowers, aborted naturally soon after pollination. However, when the lower flower buds were removed, the upper flowers produced fruit. This suggests that the upper flowers may serve as a backup if the earlier blooming lower ones are lost early in the season. Furthermore, the late-blooming flowers may still contribute to the plant's reproductive success as visiting pollinators remove the pollen, which could serve to sire fruit on other plants. These results are discussed in the context of their possible evolutionary and proximate causes.

Critical irrigation threshold and cranberry yield components

“…A significant difference in S/B was expected for the driest treatments because pollinators are generally more active in drier environments (Brown and McNeil, 2006;Pritts, 1997) and excess water may reduce nectar quality (Pritts, 1997), but this was not reflected in the results here.…”

“…Previous studies indicate that yield components are affected by diseases (Bristow and Windom, 1989), weeds (Patten and Wang, 1994a;Yas and Eaton, 1982), cultivar and geographical location (Strik et al, 1991;DeMoranville et al, 1996), as well as pollination (Shawa et al, 1981;Cane and Schiffhauer, 2003). Pollination affects the number of seeds per berry (Eaton et al, 1983), which in turn is correlated to berry size (Hall and Aalders, 1965;Eaton, 1965 could also be a source of yield components variations (Shawa et al, 1981;Birrenkott and Stang, 1990;Patten and Wang, 1994b;Brown and McNeil, 2006).…”

Proximity to forest edge does not affect crop production despite pollen limitation

“…As reported for cranberry (Cane & Schiffhauer 2003), pollen receipt must exceed a minimum threshold to elicit fruit set (Brown & McNeil 2006;Aizen & Harder 2007). In addition, the 'mass effect' produced by the simultaneous deposition of pollen on the stigma could perhaps be more important than total pollen deposition (Ganeshaiah & Shaanker 1988).…”

Water Table Control for Increasing Yield and Saving Water in Cranberry Production

“…Upward fluxes are negligible when the WTD is deeper than 90 cm (Figure 2b). Cranberry yield limitation is often explained by the low success of flowers to produce berries caused by a limited accumulation of carbohydrates [23][24][25]. Since water availability has been identified to limit carbon fixation [6], controlling the water table at a depth deeper than the optimum probably resulted in lower plant energy reserves available to set fruits.…”

“…Resource limitation has long been pointed out as a potential yield limitation factor in cranberries. Greater energy reserves stocked as carbohydrates could allow more berries to be set from flowers and then increase final yield [23][24][25]. …”