Abstract
Lettuce seedlings often require the use of fertilizers for their cultivation management to achieve appropriate yield. However, for eco-sustainable chemical-fertilizers-free agronomy, the implementation of totally organic farming often cannot support lettuce productivity, therefore new natural biostimulants able to increase lettuce yield could be considered of great interest. In this preliminary work, the foliar spray application of a Chlorella vulgaris extract in lettuce seedlings was investigated in order to achieve better yield performance. Its biostimulant effect was evaluated by monitoring the morphobiometric parameters, chlorophylls, carotenoids, total protein contents, and several enzymatic activities involved in primary and secondary metabolisms of the plant. The experimental trials were carried out by growing lettuce seedlings on inert substrate (pumice) with a 16 h photoperiod for 21 days. The treatment consisted of three consecutive applications by foliar spraying using a concentration of the C. vulgaris extract, corresponding to 1 mg Corg L−1, which were performed one week apart. The results showed that the C. vulgaris extract positively influenced the growth of lettuce seedlings, by increasing the fresh and dry weights, chlorophylls, carotenoids, protein content, and ashes at shoot level. From a biochemical point of view, primary and secondary metabolisms of shoots, in particular nitrogen metabolism, were positively influenced. At the root level, the extract increased dry matter, proteins, and ash content.
Highlights
Among vegetable crops cultivated in the Mediterranean area, lettuce (Lactuca sativa L.)often requires for its cultivation the use of biostimulants and chemical fertilizers to reach a high degree of productivity and maximum growth, since it is a crop moderately sensitive to salt [1]
These findings are in accordance with Puglisi et al [14], who found that a biostimulant extract prepared from Scenedesmus quadricauda applied by root drenching on lettuce seedlings showed better effectiveness above all at shoot level
These results suggest that the spray treatment with C. vulgaris resulted to be as effective as those performed with S. quadricauda on the lettuce seedlings at the root level
Summary
Among vegetable crops cultivated in the Mediterranean area, lettuce (Lactuca sativa L.)often requires for its cultivation the use of biostimulants and chemical fertilizers to reach a high degree of productivity and maximum growth, since it is a crop moderately sensitive to salt [1]. The implementation of totally organic farming in some regions often cannot increase lettuce productivity [2] In this respect, the application of natural biofertilizers and/or biostimulants to the agricultural field is becoming an attractive research topic. In Europe, the legislative framework on plant biostimulant is very complex, and it is regulated at a state level, since specific legislation or definitions are still not issued [4,6]. In this complex context, du Jardin [4] proposed to deem biofertilisers as a subcategory of biostimulants, which are able to increase nutrient use efficiency and allow new prospect for nutrients acquisition by plants
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