Effect of Soil K Supply and Terminal Drought on Seed Yield and Pod Set of Narrow-leafed Lupin

This experiment investigated if adding soil K could reduce the influence of terminal drought on lupin seed yield.Narrow-leafed lupin (Lupinus angustifolius L.mutant Danja abs-) was grown in a glasshouse with 3 levels of K application (0,15 and 60mg·kg-1).Drought treatment,keeping the soil water content at 40%-50% of field capacity by weighing the pots,kept on for 14 d starting at the beginning of flowering on the top branches,no watering afterwards.Application of K increased seed weight,the number of seeds per pod on the lateral branches and the number of pods on the main stem,resulting in increased seed yield,but did not affect harvest index.Increasing K supply increased above-ground biomass,K+ concentration in shoot and main stem seed,and the sucrose concentration in sap from young pods on the main stem,while decreased leaf water potential and osmotic potential.Terminal drought reduced seed yield via a reduced seed yield of the lateral branches.Terminal drought mainly decreased seed weight and the number of pods on the lateral branches,as well as above-ground biomass,although it did not affect the number of seeds per pod and harvest index.Meanwhile,terminal drought reduced leaf water potential but not osmotic potential.The results suggest that K does not compensate for the negative impact of terminal drought on seed yield of narrow-leafed lupin in this experiment.