Guy Edwardes / Close up of a sunflower (Helianthus annuus) head, Provence, France.

Guy Edwardes / Close up of a sunflower (Helianthus annuus) head, Provence, France.

Nigel Cattlin / Sunflower (Helianthus annuus) seedlings grown in light on left and without light on right, etiolated chlorotic and weak.

Nigel Cattlin / Sunflower (Helianthus annuus) seedlings in different stages of germination from seed to seedling with cotyledons, above and below ground. Sequence.

Nigel Cattlin / Sunflower (Helianthus annuus) seedling with cotyledons expanding, above and below ground. Sequence 5/5.

Nigel Cattlin / Sunflower (Helianthus annuus) seedling with cotyledons expanding, pericarp still attached to leaf. Above and below ground. Sequence 4/5.

Nigel Cattlin / Sunflower (Helianthus annuus) seedling with cotyledons expanding, leaves still trapped by pericarp. Above and below ground. Sequence 3/5.

Nigel Cattlin / Sunflower (Helianthus annuus) seed within pericarp / seed coat, radicle developing. Above and below ground. Sequence 2/5.

Nigel Cattlin / Sunflower (Helianthus annuus) seed in soil, prior to germination and growth, above and below ground. Sequence 1/5.

Nigel Cattlin / Sunflower (Helianthus annuus) seedling with expanding cotyledons. Sequence 3/3.

Nigel Cattlin / Sunflower (Helianthus annuus) seedling with expanding cotyledons, pericarp retained on leaf. Sequence 2/3.

Nigel Cattlin / Sunflower (Helianthus annuus) seedling with cotyledons still trapped inside pericarp after germination. Sequence 1/3.