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.Often Cannabisplants, even very large ones, have very small andsensitive root systems.Recently, certain alkaloidshave been discovered in the roots of Cannabis thatmight have some medical value.If this proves thecase, Cannabis may be cultivated and bred for highalkaloid levels in the roots to be used in thecommercial production of pharmaceuticals.As with many traits, it is difficult to make selections forroot types until the parents are harvested.Because ofthis many crosses are made early and seeds selectedlater.h) Branching - The branching pattern of a Cannabisplant is determined by the frequency of nodes alongeach branch and the extent of branching at eachnode.For examples, consider a tall, thin plant withslender limbs made up of long internodes and nodeswith little branching (Oaxaca, Mexico strain).Compare this with a stout, densely branched plantwith limbs of short internodes and highly branchednodes (Hindu Kush hashish strains).Differentbranching patterns are preferred for the differentagricultural applications of fiber, flower, or resinproduction.Tall, thin plants with long internodes andno branching are best adapted to fiber production; ashort, broad plant with short inter nodes and welldeveloped branching is best adapted to floralproduction.Branching structure is selected that willtolerate heavy rains and high winds without breaking.This is quite advantageous to outdoor growers intemperate zones with short seasons.Some breedersselect tall, limber plants (Mexico) which bend in thewind; others select short, stiff plants (Hindu Kush)which resist the weight of water without bending.i) Sex - Attempts to breed offspring of only one sexualtype have led to more misunderstanding than anyother facet of Cannabis genetics.The discoveries ofMcPhee (1925) and Schaffner (1928) showed thatpure sexual type and hermaphrodite conditions areinherited and that the percentage of sexual typescould be altered by crossing with certainhermaphrodites.Since then it has generally beenassumed by researchers and breeders that a crossbetween ANY unselected hermaphrodite plant and apistillate seed-parent should result in a population ofall pistillate offspring.This is not the case.In mostcases, the offspring of hermaphrodite parents tendtoward hermaphrodism, which is largely unfavorablefor the production of Cannabis other than fiber hemp.This is not to say that there is no tendency forhermaphrodite crosses to alter sex ratios in theoffspring.The accidental release of some pollen frompredominantly pistillate hermaphrodites, along withthe complete eradication of nearly every staminateand staminate hermaphrodite plant may have led to ashift in sexual ratio in domestic populations ofsinsemilla drug Cannabis.It is commonly observedthat these strains tend toward 60% to 80% pistillateplants and a few pistillate hermaphrodites are notuncommon in these populations.However, a cross can be made which will producenearly all pistillate or staminate individuals.If theproper pistillate hermaphrodite plant is selected as thepollen-parent and a pure pistillate plant is selected asthe seed-parent it is possible to produce an F1, andsubsequent generations, of nearly all pistillateoffspring.The proper pistillate hermaphrodite pollen-parent is one which has grown as a pure pistillateplant and at the end of the sea son, or under artificialenvironmental stress, begins to develop a very fewstaminate flowers.If pollen from these few staminateflowers forming on a pistillate plant is applied to apure pistillate seed parent, the resulting F1 generationshould be almost all pistillate with only a few pistillatehermaphrodites.This will also be the case if theselected pistillate hermaphrodite pollen source isselfed and bears its own seeds.Remember that aselfed hermaphrodite gives rise to morehermaphrodites, but a selfed pistillate plant that hasgiven rise to a limited number of staminate flowers inresponse to environmental stresses should give riseto nearly all pistillate offspring.The F1 offspring mayhave a slight tendency to produce a few staminateflowers under further environmental stress and theseare used to produce F2 seed.A monoecious strainproduces 95+% plants with many pistillate andstaminate flowers, but a dioecious strain produces95+% pure pistillate or staminate plants.A plant froma dioecious strain with a few inter sexual flowers is apistillate or staminate hermaphrodite.Therefore, thedifference between monoecism and her maphrodismis one of degree, determined by genetics andenvironment [ Pobierz całość w formacie PDF ]