Effects of high NH+4 on K+ uptake, culm mechanical strength and grain filling in wheat

Abstract

It is well established that a high external NH+4 concentration depresses many processes in plant development, but the underlying mechanisms are still not well understood. To determine whether the negative effects of high levels of NH+4 are related to competitive cation uptake, wheat was grown in a field with moderate (18 g N m−2) and high (30 g N m−2) supplies of NH+4 in the presence or absence of additional K+ (6 g K2O m−2) to examine culm mechanical strength, the main components of the vascular bundle, nitrogen (N) remobilization and the grain-filling rate. The results indicated that an excessive supply of NH+4 significantly decreased culm mechanical strength, the cellulose and lignin contents of vascular bundles, the N remobilization efficiency (NRE) and the grain-filling rate compared with a moderate level of NH+4. The additional provision of K+ considerably alleviated these negative effects of high NH+4, resulting in a 19.41–26.95% increase in culm mechanical strength during grain filling and a 34.59% increase in the NRE. An assay using the scanning ion-selective electrode technique (SIET) showed that the net rate of transmembrane K+ influx decreased by 84.62%, and measurements using flame photometry demonstrated that the K+ content decreased by 36.13% in wheat plants subjected to high NH+4. This study indicates that the effects of high NH+4 on culm mechanical strength, cellulose and lignin contents, the NRE and the grain-filling rate are probably associated with inhibition of K+ uptake in wheat.

Excessive nitrogen application dampens antioxidant capacity and grain filling in wheat as revealed by metabolic and physiological analyses

“…During grain filling, cereal crops begin senescence with a burst of excessive ROS such as H 2 O 2 , superoxide and its more toxic derivative hydroxyl radical 25 26 . Although N is an essential component of the proteins used to build cell materials and plant tissues, high levels of N are toxic to plant growth 2 . The toxicity of NH 4 + is likely caused by oxidative stress from the excessive accumulation of ROS 26 27 28 29 30 .…”

“…China is a major user of N fertilizers and accounts for 40% of the total global use since 2006 1 . As a consequence of excessive fertilizer use, superfluous N is lost from the plant-soil system, causing environmental damage, and lodging is a very common problem due to large populations and the inhibition of K + uptake 2 . Simultaneously, increases in the N supply promote the development of some pathogens 3 , affect plant disease resistance and increase disease susceptibility, a phenomenon called NIS (Nitrogen-Induced Susceptibility) 4 .…”

Lignins: Biosynthesis and Biological Functions in Plants

“…However, excessive nitrogen fertilizer significantly decreased the mechanical strength of stalk and the lodging resistance by reducing lignin biosynthesis in buckwheat, rapeseed and japonica rice [ 71 , 72 , 73 ]. Kong et al [ 74 ] found that the addition of K + could significantly alleviate the effect of high NH 4 + on the wheat culm strength. Therefore, it was suggested that the decrease of lodging resistance induced by nitrogen fertilizer was possibly related to the inhibition of uptake of K + which increased the lignin accumulation in the vascular bundles.…”

Genetic Diversity of Farmers’ Varieties of Rice (Oryza sativa L.) with Special Orientation to Lodging Characteristics

“…Mechanical strength is largely dependent on the chemical and biochemical components of the cell wall [7][8][9]. Generally, lignin and cellulose, which are the main biochemical components of plant tissues, particularly in the vascular bundles, are closely associated with culm mechanical strength [10].…”