Spike dry matter and nitrogen accumulation before anthesis in wheat as affected by nitrogen fertilizer: relationship to kernels per spike

In wheat crops subjected to nitrogen deficiency before anthesis, kernel num ber is reduced and is controlled by dry matter (DM) or nitrogen (N) accumul ation in spikes. We investigated spike DM and N accumulation before anthesi s under various N nutrition conditions, and the relationships between kerne l number per spike with spike DM and N content at anthesis and earlier in s pike growth period. The winter wheat cultivar Soissons was grown in fields near Paris for 2 years and was subjected to 18 treatments varying N supply. The spike DM and N content were determined twice weekly during the spike g rowth period, and kernel number was counted before maturity. All determinat ions were for main shoots only. The dynamics of DM and N accumulation diffe red greatly between treatments. The shape of the curves of spike DM and N c ontent, expressed as a percentage of the DM and N content at anthesis, were similar, but N began to accumulate before DM, whatever the treatment. The linear relationship between kernel number per spike and spike DM at anthesi s was strong and went through the origin. The relationship between kernel n umber and spike N content at anthesis was equally strong but with a positiv e intercept. These relationships with kernel number were also significant i f spike DM and N content were measured in the middle or at the beginnings o f the spike growth period. (C) 1999 Elsevier Science B.V. All rights reserv ed.