Sunflower Height and Seed Size
Sunflowers (Helianthus annuus) are ideal for studying inherited traits and variation because they grow quickly and show measurable differences between generations.
When sunflower plants produce seeds, those seeds inherit traits from their parent plants - such as height, seed size, and leaf number. However, even though offspring inherit these traits, they don’t look exactly like their parents. Within a group of related plants, variation occurs naturally.
Researchers from the USDA Plant Genetics Program measured sunflower populations grown from seeds of both tall and short parent plants. Their data showed clear patterns:
Offspring from tall parents tended to be taller on average, but not all offspring were tall.
Offspring from short parents tended to be shorter on average, but still varied in height.
Seed size also showed inheritance - large-seeded parents produced larger seeds - yet with variation across individual plants.
This variation results from a combination of genetic inheritance and environmental factors like soil, water, and sunlight. Even in the same garden, not all sunflower offspring grow exactly alike, but patterns in the data show that the traits of parents influence those of their offspring.
Table 1.
Parent Type | Offspring Height (cm) | Seed Size (g) | Parent Type | Offspring Height (cm) | Seed Size (g) |
|---|
Tall | 184.97 | 0.13 | Short | 154.66 | 0.08 |
Tall | 178.62 | 0.12 | Short | 137.74 | 0.09 |
Tall | 186.48 | 0.12 | Short | 140.68 | 0.07 |
Tall | 195.23 | 0.12 | Short | 125.75 | 0.07 |
Tall | 177.66 | 0.10 | Short | 134.56 | 0.10 |
Tall | 177.66 | 0.11 | Short | 141.11 | 0.11 |
Tall | 195.79 | 0.11 | Short | 128.49 | 0.09 |
Tall | 187.67 | 0.14 | Short | 143.76 | 0.11 |
Tall | 175.31 | 0.13 | Short | 133.99 | 0.10 |
Tall | 185.43 | 0.09 | Short | 137.08 | 0.08 |
Tall | 175.37 | 0.12 | Short | 133.98 | 0.10 |
Tall | 175.34 | 0.11 | Short | 158.52 | 0.11 |
Tall | 182.42 | 0.11 | Short | 139.87 | 0.09 |
Tall | 160.87 | 0.13 | Short | 129.42 | 0.11 |
Tall | 162.75 | 0.14 | Short | 148.23 | 0.05 |
Tall | 174.38 | 0.13 | Short | 127.79 | 0.10 |
Tall | 169.87 | 0.11 | Short | 142.09 | 0.09 |
Tall | 183.14 | 0.12 | Short | 120.40 | 0.09 |
Tall | 170.92 | 0.13 | Short | 126.72 | 0.09 |
Tall | 165.88 | 0.13 | Short | 141.97 | 0.06 |
Graph of Information - Figure 1.

Graph of Information - Figure 2.
