The heat tolerance of sunflower is considered a complex adaptive index, which lacks standardized units of measurement and is evaluated through physiological and biochemical parameters, as well as field yield stability.
In the reference
3
varieties
crop Sunflower,
where this is mentioned in the description.
There is no single heat tolerance index for sunflower that is established in the protocols for testing distinctness, uniformity, and stability (DUS). This trait is evaluated through indirect indicators, such as the accumulation of free proline in leaves, as well as through parameters of ecological plasticity and the yield stability of varieties under heat stress conditions.
High temperatures during critical developmental phases, from head formation to seed filling, negatively affect the crop's genetic yield potential and oil content. The primary natural mechanism for sunflower adaptation to heat and drought is a robust taproot system that penetrates to a depth of two meters or more, allowing the plant to effectively utilize soil moisture from deep horizons.
General information about the subject — on the page
Heat tolerance.
Varieties of Sunflower mentioned in the description
Selection based on the description text, not on official evaluation: these data are absent from registers. For specific variety details, please refer to its profile.