Response of winter barley cultivars to nitrogen and a plant growth regulator in relation to lodging
SUMMARYApplications of nitrogen and a plant growth regulator (mepiquat chloride and ethephon) were used to manipulate stem structure and induce differing degrees of damage due to leaning and lodging in six cultivars of winter barley grown in Belfast, UK, in 1986/87. Weighted incidences of leaning and lodging were combined to give an index indicating damage susceptibility of the cultivars. The index was very high (70) in Pipkin and ranged between 1 and 18 in the other cultivars. Differences between cultivars in number of internodes, plant height and stem weight did not explain their differences in resistance to damage. However, dry weight per unit length ranged from 2·35 and 2·34 mg/mm in the strongest cultivars, Panda and Jennifer, respectively, to 1·75 mg/mm in the weakest cultivar, Pipkin.Nitrogen application increased plant height but did not affect dry weight/main stem, so that dry weight/unit length of stem decreased. The growth regulator treatments reduced plant height and although dry weight/stem did not decrease significantly, dry weight/unit length of stem was similar in treated and untreated plots.Dry weight/unit length has potential as an objective indicator of straw strength in winter barley cultivars and could be used in cultivar evaluation in the absence of damage in field trials.