Question

Why do wind pollinated flowers have a single ovule in each ovary

Answer 1

Due to variation in wind speed, the pollen losses are high.  So the chances of multiple pollen grains dispersed in stigma are very less.  Thus, wind pollinated flowers have single ovule.

EXPLANATION:

Wind pollination is defined as the transfer of pollen grain through wind from anther to stigma. Wind direction and its speed is unpredictable and has variation. Therefore there is a huge loss of pollen grains as they are not being in place for germination. So having multiple ovules in each ovary is very difficult.