Powerful fertilizer for tomatoes.
Chitosan, a natural biopolymer derived from chitin, is used in agriculture as an organic fertilizer and metabolism booster. However, the effect of chitosan in different phases of plant growth and on individual plant organs has not yet been thoroughly studied. In cooperation with partners from Morocco, IPB scientists have now addressed this issue and tested the fertilizer on tomato plants at various stages of growth. According to the results, chitosan applied as a foliar spray showed positive effects that were more pronounced in the fruits than in the leaves or roots. In general, the scientists from Halle demonstrated a strong correlation between application dose and treatment duration and the effect achieved. A medium dose of chitosan led to a significant increase in fruit yield and also in the length diameter of the tomatoes, while a high dose of fertilizer caused a reduction in fruit size, which, however, had a higher sugar content. A metabolite analysis of the fruits revealed a general stimulation of primary and secondary metabolism by chitosan. Thus, after fertilizer application, the Halle scientists were able to demonstrate increased CO2 fixation, as well as enhanced nitrogen and phosphorus contents in the tomato fruits. This led to a rise in sucrose production and thus to the provision of carbon precursors for the biosynthesis of secondary metabolites such as phospholipids and antioxidants.
Positive effects were also observed in the shoots and roots of treated plants. Chitosan-fertilized plants showed an overall higher biomass; the number, areas and weight of leaves were increased. This improvement in vegetative growth under chitosan treatment was discussed in detail by the authors. As possible causes, they suggested better chloroplast function and greater dilation of stomata, leading to higher CO2 assimilation and photosynthetic activity. Root growth, on the other hand, was unaffected by the fertilizer. However, leaves and roots exhibited stronger wounding response under chitosan. The application of chitosan thus influences numerous physiological processes, such as stomata opening, cell division and expansion, fruit ripening, mineral uptake and defense reactions. Overall, the authors conclude, chitosan proves to be a useful biostimulant for tomato cultivation.
