Nitrogen availability effects on gas exchange measurements in field-grown maize (Zea mays L.) under irrigated Mediterranean conditions

Ramón Isla,Montserrat Salmerón,Mónica Guillén

doi:10.5424/sjar/2016144-9109

Abstract

There are limited studies about the effect of nitrogen (N) deficiency on leaf growth, N status, and photosynthetic capacity of maize grown under field conditions in a Mediterranean climate. The objective of this work was to evaluate the effect of different levels of mineral N availability on leaf gas exchange parameters of sprinkler irrigated maize. The experiment was conducted in a conventional maize field located in the central part of the Ebro valley (Spain) during two seasons. Using a portable LICOR-6400 equipment, instantaneous measurements and light response curves to gas exchange were conducted in plots with different levels of N supply ranging from deficient (no fertilized) to over-fertilized (300 kg N/ha). In addition to gas exchange measurements, mineral soil N content, chlorophyll meter readings (CMR), leaf N content, and grain yield were measured in the different plots. Results showed that grain yield reached a plateau (14.5 Mg/ha) when the mineral N available was about 179 kg/ha. CMR were linearly and highly related to total N in ear leaves. The relationship between light-saturated leaf photosynthesis measurements and CMR was significant but very weak (R2=0.13) at V8 and V14 stages but increased later in the growing season (R2=0.52). Plants with intermediate levels of N supply (48<CMR<54) tended to have slightly higher assimilation rates than plants with higher CMR readings. As the available N increased, the saturation point, the light compensation point and significant increases of dark respiration rate were observed. Under the conditions of the study, leaf N contents of 1.9% in the ear leaf were enough to maximize leaf assimilation rates with no need to over-fertilize the maize crop.

Highlights

Nitrogen is a major plant nutrient that is a fundamental component of leaf cell structures associated with the photosynthesis function
Using a portable LICOR-6400 equipment, instantaneous measurements and light response curves to gas exchange were conducted in plots with different levels of N supply ranging from deficient to over-fertilized (300 kg N/ha)
When comparing newer with older maize cultivars, the results indicate that genetic improvement can be partially attributed to higher leaf photosynthetic rates in newer cultivars, in particular during mid to late grain filling (‘stay green’) (Echarte et al, 2008)

Summary

Introduction

Nitrogen is a major plant nutrient that is a fundamental component of leaf cell structures associated with the photosynthesis function. It is well documented that N deficiency can lead to significant yield reductions in maize (Di Paolo & Rinaldi, 2008; Berenguer et al, 2009) as a result of reduced photosynthesis (Khamis et al, 1990; Dwyer et al, 1995; Zhao et al, 2003; Correia et al, 2005) and growth rates (Zhao et al, 2003; Hammad et al, 2012). The N concentration of expanding leaves from maize plants at different N supply was well related to light-saturated photosynthetic capacity with a hyperbolic function. Differences in photosynthetic assimilation rates in maize under different conditions of N supply are more likely to occur at high irradiance levels compared to low irradiance (Khamis et al, 1990). N limited plants can show increased intercellular CO2 concentration (Ci) (Correia et al, 2005)

Objectives

Methods

Results

Conclusion