Phyco-rrhiza: the First Report of Beneficial Microalga-Root Association of Cucumis sativus Grown on Soilless Media Under Dutch Polyhouse Conditions

Microalgae are gaining importance in the agriculture sector because of their biostimulant activities and thereby increasing crop and vegetable yields worldwide. In the current study, intact microalgal cells were used as bio-stimulants for Cucumis sativus root treatment in a soilless agricultural system inside a Dutch polyhouse along with routine nutrients. The control sets with routine nutrients and with only D/W were put to study the exact effect of microalga on the growth of the cucumber plant. The average length of the biostimulant treated cucumber climber was 12.25% more than nutrient set, which itself showed 48.28% more growth than the control set. Similarly, biostimulant treated set showed an increase in the stem diameter (10%), the number of leaves (37.66%), and the number of floral buds (39.47%) as compared to nutrient set, which themselves exhibited superior parameters than the control set. The numbers of flowers were 100% and fruits were 77.78% more in the biostimulant treated set than in the nutrient set. When the pigment profile was studied, the biostimulant treated set showed increased chlorophyll a (23.77%), chlorophyll b (68.78%) and decreased carotenoids (65.75%) content as compared to the nutrient set. Microscopic observation of roots of microalga biostimulant treated set revealed microalga-root association. To the best of our knowledge, it is the first report of the microalga-root association in C. sativus along with a positive impact on the overall growth and yield of cucumber plants under soilless conditions. The findings have the potential to lay the groundwork for a novel microbe-root interaction between microalgae and plant roots (Phyco-rrhiza).