Pre‐ and Post‐silking Carbohydrate Concentrations in Maize Ear‐leaves and Developing Ears in Response to Nitrogen Availability

Abstract

Maize (Zea mays L.) grain yield is considered to be highly associated with carbohydrate dynamics in leaves and developing ears during the critical period bracketing silking. Carbohydrate changes are sensitive to variation in nitrogen (N) availability, yet a comprehensive analysis of the N effect on various carbohydrate concentrations around silking remains elusive. A 2‐yr field study was conducted to investigate grain yield, N uptake, ear dry matter and carbohydrate concentrations in ear‐leaves and whole ears (prior to silking) and kernels (after silking) of maize grown with 0, 150, and 300 kg N ha−1. Greater N availability increased maize shoot dry matter and N content at silking and physiological maturity, as well as grain yield. While N had little effect on ear‐leaf glucose concentration, sucrose concentration increased but starch concentration decreased with increasing N, regardless of sampling time. Prior to silking, glucose and fructose concentrations in the developing ear responded positively to increasing N availability, but sucrose and starch concentrations declined. In growing kernels shortly after silking, glucose and fructose concentrations in N fertilized treatments were significantly lower than those in the zero‐N treatment. In contrast, a significant increase in kernel starch concentration was found in response to 300 kg N ha−1. These observations point to an important role of the carbohydrate composition of unpollinated ears prior to silking with regard to kernel set and post‐silking kernel starch accumulation, and thus final crop yield.

Carbohydrate Dynamics in Maize Leaves and Developing Ears in Response to Nitrogen Application

“…To provide context for the NCS and gene expression data, grain yield data are presented in Figure 1 (adapted from [8] and [13]). Briefly, compared to the N0 and N150 treatments, the final grain yield of the N300 treatment was increased by 2.1-4.3 fold in 2010 and by 1.2-2.0 fold in 2011, respectively, and significant differences were detected between N0 and N150 in 2010 ( Figure 1).…”

“…Over the past decades, numerous studies have been conducted to examine the effects of N supply on leaf growth and photosynthetic capacity [9][10][11][12], leaf carbohydrate concentrations [13][14][15], sucrose loading and transport in the phloem [8], and ear growth and carbohydrate dynamics [13][14][15][16], and how these factors influence yield and yield components. For instance, increased grain yield in response to N application was associated with greater leaf area [9][10][11], ear dry weight (DW) [13][14][15], and developing kernel number per ear [17].…”

“…Over the past decades, numerous studies have been conducted to examine the effects of N supply on leaf growth and photosynthetic capacity [9][10][11][12], leaf carbohydrate concentrations [13][14][15], sucrose loading and transport in the phloem [8], and ear growth and carbohydrate dynamics [13][14][15][16], and how these factors influence yield and yield components. For instance, increased grain yield in response to N application was associated with greater leaf area [9][10][11], ear dry weight (DW) [13][14][15], and developing kernel number per ear [17]. Enhanced maize yield with N fertilization has been positively associated with increased leaf total and soluble protein concentrations [9,14,18,19], as well as kernel soluble protein [16,20] and starch concentrations [16,21], but yield improvement was negatively related to increasing soluble carbohydrate concentrations in the developing kernels [16,21].…”

Can Late‐Split Nitrogen Application Increase Ear Nitrogen Accumulation Rate During the Critical Period in Maize?

“…Comparing 0 and 200 kg N ha −1 applied at V6, Rossini et al (2011) reported that biomass allocation to the ear during the CP was not reduced by the lower N rate. In contrast, Peng et al (2016) recently demonstrated increased ear DM 6 d before silking and 8 d after silking with a split application of 300 kg N ha −1 (150 kg ha −1 at planting, 75 kg ha −1 at V6, and 75 kg ha −1 at V10) compared with either 0 or 150 kg N ha −1 applied at planting. Examining N rates of 0 to 180 kg N ha −1 applied either at planting or V6, Uhart and Andrade (1995a) found that AEGR tended to increase with increasing N rate, but the increase in AEGR was proportional to the increase in crop growth rate.…”

Peer Review #1 of "Shoot and root traits of summer maize hybrid varieties with higher grain yields and higher nitrogen use efficiency at low nitrogen application rates (v0.1)"

“…Many studies have shown that the application of nitrogen fertilizer can improve the photosynthetic capacity, nitrogen content, total biomass, and grain yield but decrease the NUE (Peng et al, 2016;Hammad et al, 2017). Similar to previous studies, our results showed that the application of N300 increased the grain yield by 2-15% compared with N150.…”