Considering the effects of increasing heat waves already underway, especially in several
areas of the Mediterranean region, the study of the effect of temperature on the qualitative
yield of hemp oil becomes necessary. Given this, an experiment was conducted in order to
evaluate the effect of temperature during the grain-filling period on fatty acid accumulation and composition in hemp seed, comparing two locations with different temperature
regimes, two years, two sowing times and two monoecious hemp varieties, characterized
by different earliness. The accumulation of different fatty acids in hemp seeds at maturity
seems to depend on the genetic background of the two genotypes studied. However, high
temperatures also affect the activity of desaturase ∆12 and ∆15, which are responsible
for the production of polyunsaturated fatty acids, in particular if greater than an 18 ◦C
minimum night temperature and 30 ◦C maximum daily temperature, respectively. This
result makes it possible to orient, even if partially, the qualitative characteristics of hemp
oil for different uses, by identifying the suitable cultivation environment. Considering
the Mediterranean area, hilly and foothill environments would favor the percentage of
polyunsaturated fatty acid in the oil, with an improvement of the n-6/n-3 ratio, while the
plain and warmer area, characterized by heat stress during the grain-filling period, would
give an oil with an increased percentage of monounsaturated acids to the detriment of
polyunsaturated fatty acid.
