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Bee-pollinated fruits have longer shelf life

18 Feb, 2014

Strawberries grown from bee-pollinated flowers are more prolific, last longer and are better quality (as measured by colour, size, weight and lack of malformations) than those that are wind or self-pollinated according to recently published research.

Bee pollination increases crop market value

The study extrapolated further to point out that, because of these results, bees are directly contributing to world food security by reducing food wastage. (Apparently, in industrialised countries, a staggering 30–50% of all crops are thrown away at retail and consumer levels.) They calculate that the pay-off for farmers an almost 50% increase in crop market value.

Test plots and methodology

Using nine varieties of commercially grown strawberries, the team of German and Swedish scientists planted 12 test plots, with each plot containing nine randomised rows of 18 plants of a single variety and allowed them to develop flower buds. All the buds on two plants from every variety in every plot were covered with either Osmolux bags to allow only self-pollination or with gauze bags to allow self-pollination and wind pollination. The bags were removed after fruit had set – normally around 7 days after the flowers had opened. Five established honeybee hives as well as some 300 trap nests were located nearby to ensure pollination services for the remaining plants.

The researchers found the bee-pollinated fruit was 11% heavier than wind-pollinated fruit and 30.3% heavier than self-pollinated fruit. Seven of the nine varieties had a “more intense red colour”, and all bee-pollinated fruit had fewer malformations and so commanded a higher price – some 39% more than wind-pollinated strawberries and 54% more than self-pollinated strawberries.

Pollen distribution and fruit quality

The weight and malformation issue is interesting. It appears the bees make a better job of distributing pollen homogeneously on the receptacles of strawberry flowers, increasing the number of fertilised achenes per fruit. Achenes are the little seed-like true fruits on the outside of the strawberry – the big red part is actually just the receptacle for these tiny true fruits.

“While unfertilized achenes resulting from insufficient pollination have no physiological functionality, fertilized achenes produce the plant hormone auxin, which mediates the accumulation of gibberellic acid. Together, these plant hormones induce fruit growth by improving cell progeny and size, thereby enhancing the weight of strawberry fruits. This further improves fruit quality and thereby commercial grades by preventing malformations, which are caused by areas of unfertilized and thus physiologically inactive achenes,” write the researchers in their published paper.

Firmer flesh means a longer shelf life

Importantly, the bee-pollinated crops also have at least a half-day longer shelf life over wind-pollinated fruit and a day longer than self-pollinated fruit because of their firmer flesh. This may not seem much, but a normal shelf life might only be 4 days in storage before becoming non-marketable, and this bonus time reduces wastage by at least 11% they calculated – adding some US$320 million to the European economy.

Implications for other crop species

The findings are apparently translatable to other bee-pollinated fruit and vegetable varieties, which account for some 70% of all major crop species. The researchers concluded, “Pollination appears to be economically much more important than previously recognized and needs better support through adequate agricultural management and policy.”

Get information sheet: Mendel’s experiments

The research was published in the 22 January 2014 issue of the Proceedings of the Royal Society B: Biological Sciences.

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