Cannabis sativa L. serves diverse purposes—from fiber and seed oil production to medical and recreational use—each of which depends heavily on the timing and density of its female flowers. The shape and compactness of inflorescences directly affect yield and the concentration of bioactive compounds like THC and CBD. While early flowering is known to proceed independently of photoperiod, the factors that drive full floral maturation have remained obscure. Gibberellins have long been implicated in flowering control across plant species, but their precise role in cannabis has been murky. Due to these complexities, further in-depth research is needed to unravel the interplay between photoperiod and hormones in cannabis flower development.
A research team from the Volcani Institute in Israel has uncovered critical mechanisms behind cannabis flowering, as reported (DOI: 10.1093/hr/uhae245) in Horticulture Research on September 3, 2024. By combining light cycle experiments with hormone treatments and detailed physiological analyses, the team showed that short-day (SD) photoperiods initiate and sustain inflorescence development by keeping gibberellin levels low. Reversing light conditions or applying gibberellin externally disrupts this balance, leading to elongated stems and scattered flowers. These findings redefine how we understand cannabis reproductive biology and open new pathways for agricultural optimization.
The study revealed a two-phase response to SD lighting in mature cannabis plants. Initially, plants undergo a growth spurt with rapid stem elongation, but by day 10, internode elongation halts and compact flower clusters begin to form. This transition correlates with declining levels of GA4 and auxin in the shoot apex.
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