Lodging Resistance of Japonica Rice (Oryza Sativa L.): Morphological and Anatomical Traits due to top-Dressing Nitrogen Application Rates

Abstract

BackgroundLodging in rice production often limits grain yield and quality by breaking or bending stems. Excessive nitrogen (N) fertilizer rates are the cause of poor lodging resistance in rice, but little is known about the effect of top-dressing N application rates on the mechanical strength of japonica rice plants, especially how the anatomical structure in culms is affected by N. In this study, field experiments on two japonica rice varieties with three top-dressing N application rates, 0 kg N ha−1 (LN), 135 kg N ha−1 (MN), and 270 kg N ha−1 (HN) as urea, were conducted. Wuyunjing23, a lodging-resistant japonica rice cultivar and W3668, a lodging-susceptible japonica rice cultivar were used. The lodging index, breaking strength, morphological and anatomical traits in culms were measured in this study.ResultsThe visual lodging rate in japonica rice differed remarkably between genotypes and top-dressing N treatments. The higher lodging index of rice plants was primarily attributed to the weak breaking strength of the lower internodes. The longer elongated basal internodes were responsible for higher plant height and a higher lodging index. Correlation analysis showed that breaking strength was significantly and positively correlated with the thickness of the mechanical tissue but was significantly and negatively correlated with the inner diameter of the major axis (b2). With increasing top-dressing N rates, the sclerenchyma cells of the mechanical tissues and the vascular bundles of the Wuyunjing23 cultivar varied little. The plant height, inner diameter of the minor axis (a2) and b2 increased significantly, but the area of the large vascular bundle (ALVB) and the area of the small vascular bundle (ASVB) decreased significantly and resulted in lower stem strength and a higher lodging index under higher top-dressing N conditions. The culm diameter of the W3668 cultivar increased slightly with no significant difference, and the sclerenchyma cells in the mechanical tissues and vascular bundles showed deficient lignifications under high top-dressing N conditions. Moreover, the ALVB and the ASVB decreased significantly, while the area of air chambers (AAC) increased rapidly.ConclusionsAn improvement in the lodging resistance of japonica rice plants could be achieved by reducing the length of the lower internodes, decreasing the inner culm diameter and developing a thicker mechanical tissue. Top-dressing N application increased the plant height and inner culm diameter and decreased the ALVB and the ASVB of the Wuyunjing23 cultivar and caused deficient lignified sclerenchyma cells, lowered the ALVB and the ASVB, and increased the AAC of the W3668 cultivar resulting in weaker stem strength and a higher lodging index.

Optimization of plant density and nitrogen regimes to mitigate lodging risk in wheat

“…Most of the findings from previous studies are in line with our findings that basal internode length is responsible for higher plant height, which ultimately reduces bending strength of cereals (Zhang et al, 2017a). The results of Zhang et al (2016), which are in agreement with our findings, reported that higher application of N increased the internodes length in rice (Oryza sativa) and resulted in lodging.…”

Slight Shading Stress at Seedling Stage Does not Reduce Lignin Biosynthesis or Affect Lodging Resistance of Soybean Stems

“…Xylem is a transport tissue and also the support structure of plants. Studies have shown that xylem area and xylem proportion are remarkably positively correlated with lodging resistance [30], while pith area and pith proportion are negatively correlated with lodging resistance [31]. Therefore, we measured these indicators.…”

Unravelling the Roles of Nitrogen Nutrition in Plant Disease Defences

“…In another study, high N fertilization resulted in a reduction in the thickness of the secondary cell wall as well as major biopolymer components (cellulose and lignin) in two japonica rice cultivars [57]. Interestingly, agronomically reducing the N fertilization rate can effectively increase plant lodging resistance, which is associated with changes in stem lignification and secondary cell wall synthesis and also emphasizes the negative correlation between N availability and plant epidermal hardness [58,59].…”