Cannabis sativa: Encyclopedia II - Cannabis sativa - Plant physiology

Cannabis sativa - Plant physiology

Cannabis reproduces sexually. The flowers of the female plant, in cannabis usually called buds, are arranged in racemes and can produce hundreds of seeds. Males reach sexual maturity several weeks prior to females. Although genetics disposes a plant to become male, environmental factors, including the diurnal light cycle, can alter the sex. Natural hermaphrodites, with both male and female parts, are either sterile or fertile but artificially induced hermaphrodites can have fully functional reproductive organs. 'Feminized' seed sold by many commercial seed suppliers are derived from artificially hermaphrodytic females that lack the male gene or by treating the seeds with hormones or silver thiosulfate.

A cannabis plant in the vegetative growth phase of its life cycle can thrive under twenty-four hour daylight conditions, although some growers advocate a small rest period to avoid overstressing the plant. Flowering usually occurs when darkness exceeds eleven hours per day. The flowering cycle can last anywhere between six to twelve weeks, depending on the strain and environmental conditions.

In soil, the optimum pH for the plant is 6.5 to 7.2. In hydroponic growing, the nutrient solution is best at 5.2 to 5.8, making cannabis well-suited to hydroponics because this pH range is hostile to most bacteria and fungi.

• Cultivars primarily cultivated for their fibre, characterized by long stems and little branching.
• Cultivars grown for seed from which hemp oil is extracted.
• Cultivars grown for medicinal or recreational purposes. A nominal if not legal distinction is often made between hemp, with concentrations of psychoactive compounds far too low to be useful for that purpose, and marijuana.

Adapted from the Wikipedia article "Plant physiology", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki