What impact does spraying sugarcane crops with gibberellins have on stem length and yield?

It increases stem length and yield

The correct answer is Option (3) -It increases stem length and yield

Gibberellins are another kind of promotory PGR. There are more than 100 gibberellins reported from widely different organisms such as fungi and higher plants. They are denoted as GA₁, GA₂, GA₃ and so on. However, Gibberellic acid (GA₃) was one of the first gibberellins to be discovered and remains the most intensively studied form. All GAs are acidic.

They produce a wide range of physiological responses in the plants. Their ability to cause an increase in length of axis is used to increase the length of grapes stalks. Gibberellins, cause fruits like apple to elongate and improve its shape. They also delay senescence. Thus, the fruits can be left on the tree longer so as to extend the market period.

GA₃ is used to speed up the malting process in brewing industry. Sugarcane stores carbohydrate as sugar in their stems. Spraying sugarcane crop with gibberellins increases the length of the stem, thus increasing the yield by as much as 20 tonnes per acre.