From flower to fruit.

Step 1 of 6

A seed factory

A flower looks like decoration, but every part of it is there to make seeds. From the outside in: the green sepals wrapped the bud, and the petals attract insects with colour and scent. Inside stand the stamens, the male parts, each topped by an anther that releases pollen. In the middle stands the pistil, the female part: on top the sticky stigma that catches pollen, below it the style, and at its base the ovary, with the ovules inside. The flower in the Scene has $12$⁠ ovules.

Pollination is anything that carries pollen from an anther to a stigma. Here the bee did it, and it still hovers by the flower. Turn the flower and look at the cut, then answer.

Step 2 of 6

A tube for every ovule

A pollen grain cannot move. When it lands on a stigma of its own species, it takes up water and grows a pollen tube, a single long cell that grows down the style, with two sperm cells at its tip. When the tube reaches an ovule, one sperm cell fertilises the egg cell, and the other joins a large cell in the middle of the ovule that will become the endosperm, the seed’s food store: double fertilisation. Here Pollen grains is fixed at $30$⁠, the most it goes.

Step 3 of 6

The race

The tubes grow at slightly different speeds, and the first to reach the ovary take the ovules. Drag Time slowly from Pollination and watch on the chart as the tubes grow and the ovules are fertilised one after another.

Step 4 of 6

Too few seeds

Time is now at Ripe fruit, and Pollen from is fixed on another plant. Growing seeds make hormones that swell the fruit around them, and a fruit with few seeds is not worth the food it costs the plant. Lower Pollen grains and watch when the plant gives up on the fruit.

Step 5 of 6

Half the ovules

Time is now locked at Pollination, and only $7$⁠ grains have landed on the stigma. One grain in seven grows no tube, so only half the ovules will be fertilised. Predict what kind of fruit comes of it.

Step 6 of 6

Pollen from the same plant

This time all the pollen is from The same plant: the bee went between flowers of one plant. For most species that is no use. A plant that fertilises itself mixes only its own genes, and its offspring are very like it. Predict what happens to this pollen.