Effects of Ethephon on the Pattern of Flowering and Fruit Set of Summer Squash

The plant growth regulator 2-chloroethylphosphonic acid (ethephon) was applied to summer squash to determine its effects on the flowering pattern. Treatments with all pistillate flowers pruned at anthesis, with and without ethephon applications were also compared to control plants to investigate the factors regulating flowering and fruit set of summer squash.

It was found that plants in the pruned treatments had a greater carbohydrate accumulation than plants in the nonpruned treatments, indicating that carbohydrate accumulation may be inversely associated with fruit development. Ethephon treatments produced more pistillate flowers per plant but also had a large number of aborted flowers. Thus, the potential of ethephon to increase yield has not been fully realized because the plant cannot support the added fruit.

Another observation noted was the production of hermaphroditic flowers on a monoecious summer squash cultivar. These flowers were produced when the effect of the ethephon on the plant was diminishing. Also, flowering and yield exhibited a cyclic pattern throughout the season, but no correlation was found to exist between flowering and/or yield and any plant nutrient content (carbohydrate, nitrate, calcium, magnesium, phosphorus, potassium, and nitrogen).