A mutant gene in Hordeum vulgare produces albino seedlings at temperature below 8°C. But when the seedling carrying this gene are grown at 19°C or above, they develop into normal green seedlings. The characters whose development depends upon a specific environment are known as

Solution (By Examveda Team)

Discrete characters are traits that have distinct, separate categories (like flower color being red or white).
They don't change based on the environment in the way described in the question.

Quantitative characters are traits that can be measured on a continuous scale (like height or weight).
They are usually influenced by many genes and the environment, but this question describes a very specific temperature trigger.

Threshold characters are traits that only express themselves when a certain environmental condition is met or exceeded.
In this case, the green color develops only when the temperature is above a certain threshold (8°C). Below that, the albino (white) trait appears.
This perfectly matches the description in the question!

Pleiotropy is when a single gene affects multiple different traits.
The question only describes one visible trait (color), so pleiotropy doesn't fit.

Therefore, since the albino seedling only turns green above a specific temperature, the character's development is dependent on crossing a temperature threshold.