Applied on the soil or on the plant’s leaves, biostimulants have a broad spectrum of action: quality of the harvest, increase in the level of chlorophyll and photosynthesis, availability of nutritive elements in the soil and efficacy of their use and improved capacity to withstand biotic and abiotic stresses.

Among these stresses, dryness (or hydric stress) is one of the major factors limiting the yield of harvests. This is why, at the moment, a large number of biostimulants are reaching the market with the claim of a positive impact against this stress.

Of all the biostimulants from seaweed extracts, those of Ascophyllum nodosum are the ones that have been most studied to date. The benefits of this seaweed have been demonstrated on plants’ vegetative growth, the quality of the fruits as well as the resistance to certain abiotic stresses including hydric stress. This resistance involves several factors:

• The strengthened osmo-regulation capacity of seedlings in a period of drought thanks to an increase in the quantity of solutes in the plant.
• The increase in stomatal conductance leading to better thermoregulation in case of strong heat and better photosynthetic recuperation of seedlings in a recovery phase. This improvement is due to the product’s action on the biosynthesis of abscisic acid (ABA) responsible for the closure of stomas.
• The product’s involvement in the antioxidant activity of seedlings and on the expression of certain genes responding to stress (ABA pathway).
• The activation of certain precursors enabling the seedling to protect its foliar tissue against ROS (Reactive Oxygen Species) formed during stress.

Seaweed-based biostimulants therefore act on different mechanisms in plants, which enables them to increase their capacity for resistance in a hydric stress phase and recuperate more quickly in recovery. These effects are sometimes difficult to observe or may vary under production conditions. It is therefore important to pursue the R&D efforts in this field to use them optimally.

SHUKLA PS, SHOTTON K, NORMAN E, NEILY W, CRITCHLEY AT, PRITHIVIRAJ B. SEAWEED EXTRACT IMPROVE DROUGHT TOLERANCE OF SOYBEAN BY REGULATING STRESS-RESPONSE GENES. AOB PLANTS [INTERNET]. 2018 [CITÉ 17 FÉVR 2021];10(PLX051)

TOMBESI S, FRIONI T, SABBATINI P, PONI S, PALLIOTTI A. ASCOPHYLLUM NODOSUM EXTRACT IMPROVES LEAF THERMOREGULATION BY REDUCING STOMATAL SENSITIVITY TO VPD IN VITIS VINIFERA L. J APPL PHYCOL [INTERNET]. 2020 [CITÉ 17 FÉVR 2021]

XU C, LESKOVAR DI. EFFECTS OF A. NODOSUM SEAWEED EXTRACTS ON SPINACH GROWTH, PHYSIOLOGY AND NUTRITION VALUE UNDER DROUGHT STRESS. SCIENTIA HORTICULTURAE. 12 FÉVR 2015;183:39‑47.