Evaluation of Borage Extracts As Potential Biostimulant Using a Phenomic, Agronomic, Physiological, and Biochemical Approach

Abstract

Biostimulants are substances able to improve water and nutrient use efficiency and counteract stress factors by enhancing primary and secondary metabolism. Premise of the work was to exploit raw extracts from leaves (LE) or flowers (FE) of Borago officinalis L., to enhance yield and quality of Lactuca sativa ‘Longifolia,’ and to set up a protocol to assess their effects. To this aim, an integrated study on agronomic, physiological and biochemical aspects, including also a phenomic approach, has been adopted. Extracts were diluted to 1 or 10 mL L–1, sprayed onto lettuce plants at the middle of the growing cycle and 1 day before harvest. Control plants were treated with water. Non-destructive analyses were conducted to assess the effect of extracts on biomass with an innovative imaging technique, and on leaf photosynthetic efficiency (chlorophyll a fluorescence and leaf gas exchanges). At harvest, the levels of ethylene, photosynthetic pigments, nitrate, and primary (sucrose and total sugars) and secondary (total phenols and flavonoids) metabolites, including the activity and levels of phenylalanine ammonia lyase (PAL) were assessed. Moreover, a preliminary study of the effects during postharvest was performed. Borage extracts enhanced the primary metabolism by increasing leaf pigments and photosynthetic activity. Plant fresh weight increased upon treatments with 10 mL L–1 doses, as correctly estimated by multi-view angles images. Chlorophyll a fluorescence data showed that FEs were able to increase the number of active reaction centers per cross section; a similar trend was observed for the performance index. Ethylene was three-fold lower in FEs treatments. Nitrate and sugar levels did not change in response to the different treatments. Total flavonoids and phenols, as well as the total protein levels, the in vitro PAL specific activity, and the levels of PAL-like polypeptides were increased by all borage extracts, with particular regard to FEs. FEs also proved efficient in preventing degradation and inducing an increase in photosynthetic pigments during storage. In conclusion, borage extracts, with particular regard to the flower ones, appear to indeed exert biostimulant effects on lettuce; future work will be required to further investigate on their efficacy in different conditions and/or species.

Transcriptional Regulation in Rocket Leaves as Affected by Salinity

“…The same effect observed in chlorophyll concentration was found also in carotenoids level and it makes sense because of their role as accessory light-harvesting pigments and protecting chlorophyll molecules. These results were compatible with those obtained by Bulgari et al [25] after two applications of the same borage extract on rocket and lettuce plants grown under non-stressful conditions. No significant modification of chlorophyll and carotenoids content were also detected in Eruca sativa Mill.…”

“…Moreover, plant response was analyzed in terms of change in different physiological parameters, such as chlorophyll, chlorophyll a fluorescence, carotenoids, phenols, and anthocyanins. The borage extract used in this experiment showed positive effect both on primary and secondary metabolism of lettuce and rocket plants grown under non-stressful conditions in previous experiments [25].…”

Biostimulants Application in Horticultural Crops under Abiotic Stress Conditions

“…The mechanisms activated by biostimulants are often difficult to identify and are still under investigation [58]. High-throughput phenotyping and omic technologies seem to be useful approaches to understand biostimulants activity and hypothesize a mode of action [59][60][61]. They can act directly on plant physiology and metabolism by improving soil conditions [62,63].…”

Applications of Fungal Strains with Keratin-Degrading and Plant Growth Promoting Characteristics

“…A recent systematic approach highlights the contribution of investigation and understanding of biostimulant 2 of 19 mechanisms and their mode of action [10]. This work includes comprehensive reviews on economic and environmental benefits of biostimulant use, obtainment of higher yields of cultivated plants with improved quality, decreasing of nitrate level according to EU regulation, reducing energy consumption and utilizing resources more efficiently [11][12][13][14].…”