Root and Shoot Growth of Oat Plants Treated with CCC and Ethephon

Abstract

The plant growth regulators (PGRs) are used on cereals primarily to reduce stem height and hence, prevent lodging. Recently interest has grown to modify canopy structure, root performance, and root/shoot ratios by use of PGRs. However, this may result in a need for reconsideration of the application time of the PGRs. Two preliminary trials were carried out in a greenhouse, in which three oat cultivars were used to evaluate the effect of early application (at 2–3 leaf stage) of chlormequat chloride (CCC) (1%) and ethephon (0.5%) on root and shoot growth. The cultivars that were included in this study represent differences in growth habit: Jalostettu maatiainen is an old, long-strawed and lodging-sensitive landrace cultivar, Salo is a modera high yielding cultivar with relative short and stiff straw, and Pal is a Minnesota-adapted dwarf cultivar. Oat seeds were sown in 5 L pots containing clay illitic top soil from the experimental fields. Fifteen seeds were sown per pot, but when the seedlings had emerged, plants were thinned to ten per pot. Cultivars were set as a main plot and treatments were split across them with five replicates. Pots were placed in a container (120×180cm), and hence they received continuos ground watering. At two to three leaf stage, plants were sprayed with a battery operated small scale atomizer at the rate of 10 ml of PGR per pot. Control plants were excluded. Two weeks after treatments, the above ground plant parts were cut and roots were washed carefully to remove the soil. Root and shoot samples were dried overnight at lOOEC to determine their dry weight (mg/plant). CCC as well as ethephon reduced root and shoot growth of all three cultivars. This may have resulted from a too high application rate (I ml per plant). Neither CCC nor ethephon have affected the root/shoot ratio. CCC had more deleterious effects when compared to ethephon. Root growth of the landrace and modern cultivar, was more sensitive to CCC application, at early growth stages, as compared to the response of the dwarf cultivar Pal.