Metabolic Changes in Sugarcane Bud Sprouting Stimulated by Microalga Asterarcys quadricellulare

The use of single-bud sugarcane propagules brings a challenge concerning the initial sprouting, as the physiological ages of buds affect their outgrowth. This work is addressed to stimulate the sugarcane buds sprouting in a nature-friendly way using microalgae biomass. A metabolomics approach, connecting physiological and phenotypic changes, was adopted to identify the microalgae effect on sugarcane sprouting. For that, initially the changes in propagules metabolites according to their size and bud position in culm were determined. Then, single-bud propagules from apical, medial and basal segments of culms from cv. RB036152 were immersed in a solution containing microalgae biomass. Budding percentage, sprouts size and changes in sprouts and propagules metabolites—free amino acids; total soluble, reducing and non-reducing sugars; phenolic compounds; polyamines—putrescine, spermine, spermidine; tryptophan, 5-hydroxytryptamine (serotonin) and tryptamine—were determined. Data indicated that bud outgrowth is accompanied by the increase in its amino acids and non-reducing sugars accumulation at the early stages of budding. The propagules immersion in the suspension of green microalgae Asterarcys quadricellulare (CCAP 294/1) biomass improved bud sprouting percentage and promoted remarkable sprouts growth, increasing spermidine and reducing putrescine content in sprouts, thus indicating the polyamines as the key compounds of nitrogen metabolism related to sugarcane sprouting and sprouts growth, a pathway that was triggered by microalgae biomass.