Dry-Matter Partitioning across Parts of the Wheat Internode during the Grain Filling Period as Influenced by Fertilizer and Tillage Treatments

Dry-matter transportation and redistribution is an important factor influencing grain weight during the grain filling period. This study, carried out over two consecutive winter wheat growth seasons (2010/2011 and 2011/2012), examined how dry-matter partitioning across segments of the wheat internode during grain filling period is influenced by fertilizer and tillage treatments. The contributions of current assimilates and remobilization of dry matter to final grain weight were calculated. To precisely illustrate the changes in dry matter during the grain filling period, the whole wheat stem was divided into two parts, the top three part and bottom two part. The former included three segments: the exposed part of the uppermost internode (EXUI), the enclosed part of the uppermost internode (ENUI), and the penultimate internode (PI). The latter included two segments: the lower internode (ERI) and the lowest internode (ESTI). During postanthesis, two different phases characterized by different rates of dry-matter accumulation could be distinguished. The first phase was the dry-matter accumulation; the second phase was mobilization to grains. The bottom two parts contributed more dry matter during pre-anthesis to the final grain; on the other hand, the top three parts contributed more dry matter to the final grain during postanthesis. On average, for the bottom two parts, the ERI segment had the greatest contribution of pre-anthesis dry matter to grain weight (CRAP) (3.68% in 2010/2011 and 5.31% in 2011/2012 growth seasons). For the top three parts, the EXUI segment had the greatest contribution of postanthesis photosynthetic assimilate to grain weight (CAPA) (99.71% in 2010/2011 and 99.08% in 2011/2012 growth season). The top three parts achieved maximum dry weight at 15 days after anthesis (daa), 5 days earlier than the bottom two parts. The heavy rainfall in the late grain filling period of 2011/2012 growth season inhibited postanthesis dry mobilization, and to maintain the grain filling requirements, more dry matter stored during pre-anthesis was redistributed. The present results suggest that rainfall occurring late in the grain filling period may have adverse impact on postanthesis accumulation. To avoid this phenomenon, early sowing with plastic film cover and split nitrogen application may be recommended. Fertilizing with 195 kg hm(-2) (120 + 75) N plus 45000 kg hm(-2) of ox manure and 120 kg hm(-2) phosphate with wheat straw retention during the summer fallow period under conservation minimum tillage produced the greatest stem dry matter at anthesis.