The Effect of Iron Deficiency on Photosynthesis in Soybean

Abstract

Sustainable development Goal 2 (zero hunger) composed by the United Nations focuses on improving agriculture to increase food security. One of the potential improvements to agriculture is specialised fertiliser rich in micronutrients, which are essential elements necessary for the healthy development of plants. Iron (Fe) deficiency is a known problem in crop production. A promising new development to limit iron deficiency is the use of the iron fertiliser N,N’-bis(2-hydroxybenzyl)ethylenediamine-N,N’-diacetic acid (FeHBED). FeHBED is an organic molecule able to bind iron ions, increasing available iron. Most agricultural systems in developing countries, however, are unable to use fertiliser. These countries suffer most from Fe deficiency and gain the most from an improved understanding of plant processes. The literature is lacking in data on photosynthesis parameters Jmax and Vcmax. This thesis therefore aims to answer the following question: What is the effect of iron deficiency on photosynthesis parameters (Vcmax and Jmax) in soybean (Glycine max) under different iron and light conditions over time?

Our experiment used two climate cabinets with different light intensities (140–240 µmol/m2/s) and iron conditions. Four soybean populations of 14 plants apiece were grown over a period of 37 days. Two destruction events took place: one at 18 days after the start of the experiment and one at 37 days. Measured were the maximum electron transport rate (Jmax) and the maximum carboxylation rate (Vcmax), which are critical photosynthesis parameters. Other data collected was the total leaf area, stem length and dry matter used for above- and below-ground measurements of 24 plants. The same occurred on Day 37, when all 30 remaining plants were destroyed. A database was compiled and analysed through MATLAB, R and ImageJ.

Our results showed that Fe fertiliser HBED had a significant effect on biomass at both destructions, while Vcmax was not significantly impacted. Jmax was negatively impacted at the second destruction, indicating that non-FeHBED plants under low light intensity have a higher Jmax , which could be a stress reaction to iron deficiency. This thesis provides useful insights into previous experiments, notably the behaviour exhibited by Jmax and Vcmax as a result of FeHBED in soybean. The resulting database adds to the current understanding of the effects of FeHBED in plants.

Developing countries suffer from Fe deficiency. A society aware of the behaviour of plant processes under this stress can detect and take sustainable intensification measures using FeHBED to prevent further Fe deficiency in crops.