Auxins are among the most widely used synthetic plant hormones. Common synthetic auxins include Indole Butyric Acid (IBA) and Naphthalene Acetic Acid (NAA).

Key Applications

Rooting in cuttings: Synthetic auxins stimulate root development from stem cuttings, which is essential for vegetative propagation of crops like cassava, tea, and coffee. This method preserves the genetic characteristics of superior plant varieties.

Fruit setting: Synthetic auxins promote fruit development without fertilization (parthenocarpy) in tomatoes and peppers, leading to earlier and more abundant harvests.

Weed control: Phenoxyacetic acid derivatives act as selective herbicides, killing broad-leaf dicotyledonous weeds in cereal crops like maize and rice while sparing the crops themselves.

Preventing pre-harvest fruit drop: NAA is applied to apple, citrus, and mango trees to reduce premature fruit falling, maximizing yield during harvest.

Gibberellins (particularly Gibberellic Acid, GA) are commercially produced from fungal cultures and have several agricultural uses.

Key Applications

Breaking seed dormancy: Applied to seeds of cereals and legumes to promote uniform germination, especially when seeds have been stored improperly.

Fruit setting and enlargement: Used in grape production to produce larger, seedless fruits and in mango trees to improve fruit set.

Malting in brewing: Gibberellins enhance the malting process in barley, which is essential for Tanzania's brewing industry.

Reversing dwarfism: Applied to genetically dwarf crop varieties to promote stem elongation and increase biomass yield.

Cytokinins promote cell division and delay leaf and fruit senescence.

Key Applications

Prolonging shelf life: Applied to fresh produce such as cabbage, lettuce, and cut flowers to maintain freshness during transport and storage.

Breaking bud dormancy: Used in potato seed tubers to ensure uniform sprouting after storage.

Ethylene is unique because it exists as a gas. Synthetic ethylene-releasing compounds are used for fruit ripening and flowering control.

Key Applications

Fruit ripening: Applied to bananas, tomatoes, and mangoes to achieve uniform ripening within 2-3 days, which is crucial for market distribution.

Citrus colour development: Sprayed on oranges and tangerines to develop attractive colour before sale.

Inducing flowering: Used in pineapple plantations to synchronize flowering, making harvest management easier for Tanzanian farmers.

ABA is a growth inhibitor produced in response to environmental stress.

Key Applications

Controlling fruit drop: Sprayed on tree crops such as coffee and citrus to synchronize fruit falling at season's end, allowing single harvest rather than multiple pickings.

A farmer in Morogoro applies NAA (synthetic auxin) to tomato plants immediately after flowering. This treatment:

1. Promotes fruit set without pollination
2. Reduces flower and young fruit drop
3. Produces larger, more uniform tomatoes
4. Results in earlier harvest by 7-10 days

The farmer can then sell the produce at higher prices when market supply is still low, increasing profit margins.

In Tanzania, synthetic phytohormones are directly applicable to smallholder farming. For example, a tomato farmer in Arusha can apply synthetic auxin (NAA) to reduce flower drop during the dry season, potentially increasing yield from 10 to 15 tonnes per acre. This translates to higher income when selling at local markets such as the Dar es Salaam Kariakoo market, where better-quality produce commands premium prices.