The Control of Growth Habit of Marquillo x Kenya Farmer Wheat Dwarf I by Temperature

The Marquillo x Kenya Farmer 1 "grass-clump" dwarf selection of Triticum aestivum L. was grown under continuous 2000 foot candle light and several regimes of alternating 16 degrees and 26 degrees temperatures combined in total cycle lengths of 6, 12, 24, or 48 hr. Plants at 26 degrees grew as normal wheat. Those exposed to 0.25 to 2 hr of 16 degrees per cycle showed typical "grass-clump" dwarf characteristics which were independent of the cycle length. Treatments with 16 degrees exposures of 4 to 8 hr per 24 hr and 12 to 16 hr per 48 hr exhibited vegetative "grass-clump" dwarfness for 40 days but later displayed extensive reproductive development. Longer 16 degrees treatments killed the plants at a very early stage of vegetative development before floral initiation. The data supported an hypothesis that all 4 growth habits were related to the temperature sensitivity of the vegetative meristem. The cessation of meristem development was possibly due to the accumulation of a stable inhibitory substance produced at low temperatures.