The spike weight contribution of the photosynthetic area above the upper internode in a winter wheat under different nitrogen and mulching regimes

Besides leaves, non-foliar green organs such as stem and spike are also considered photosynthetic organs. To assess the photosynthetic contributions of these organs, the correlations between these photosynthetic areas and single-spike weight were investigated in a winter wheat (Triticum aestivum L.) under four nitrogen and mulching treatments: N120, N150, N195, and N195 + M. Two-year repeated field experiments were conducted on the Loess Plateau of China. Non-foliar photosynthetic area, grain-filling ratio and duration, grain yield, and in particular, single-spike weight, were measured, recorded and analyzed. Under the N195 + M treatment, plants showed the largest area of photosynthetic organs (flag leaf and non-foliar organs) and the highest grain yield and single spike weight. Single-spike weight was positively correlated with the areas of all examined non-foliar photosynthetic organs, in particular with the area above the flag leaf node (R-2 = 0.761*) and the area above the exposed part of the peduncle (EXP) (R-2 = 0.800**). In addition, single-spike weight was highly correlated with average grain-filling ratio (R-2 = 0.993**), whereas it was less highly correlated with grain-filling duration (R-2 = 0.533). The morphological traits of non-foliar photosynthetic organs were also more highly correlated with average grain-filling ratio than with average grain-filling duration. The significant correlation between each of the morphological traits (area, length and width) of EXP and single-spike weight indicates that morphological traits of EXP are important in determining spike weight in the Loess Plateau environment. (C) 2018 Crop Science Society of China and Institute of Crop Science, CAAS. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.