Modification by gibberellin of the growth-temperature relationship in mutant and normal genotypes of several cereals

摘要

High-resolution growth measurements were conducted using a linear variable displacement transformer in conjunction with a temperature-programmed meristem-cooling collar. Chilling and rewarming profiles were determined for a range of Gramineae, in the presence and absence of varying concentrations of gibberellic acid (GA3). In wheat (Triticum aestivumL.) seedlings, the growth-constraining temperature (Pe) was progressively lowered by increasing GA3concentration, with a difference of-4.8°C between controls and material treated with 10−4M GA3.Dwarf-5maize (Zea maysL.) seedlings had a higher Pethan tall segregates and the difference was markedly reduced by exposure to a saturating concentration of GA3. A similar effect was observed with Tanginbozu dwarf rice (Oryza sativaL.). The growth ratetemperature responses ofRht3gibberellin-insensitive dwarf wheat seedlings were unaffected by GA3and the Pevalues for these segregates were around 5° C higher than for normals. Slender (s1) barley (Hordeum vulgareL.) genotypes had Pevalues of-7° C, compared with +4° C for wild-type material, and did not show positive hysteresis for growth rate during the rewarming phase. These studies indicate that GA3modifies the thermal sensitivity of meristem function in Gramineae in a manner which enhances low-temperature g