Plant growth promoter

A plant growth promoter, comprising:

• a lignocellulosic biomass (A);
• and
• at least one base (B) selected from the group consisting of base (B1-1), base (B2-1), base (B2-2), base (B2-3), base (B2-4), base (B3-1), and base (B3-2);
• wherein:
• the plant growth promoter has a contact angle with water of 80° or less;
• the lignocellulosic biomass (A) is a hydrophilic lignocellulosic biomass obtained by an alkali hot water treatment, in which a precursor lignocellulosic biomass is brought into contact with an alkaline medium with a pH of 9 to 14 at a temperature of 25 to 150° C. for 0.5 to 12 hours;
• the lignocellulosic biomass (A) has an average particle size of 0.1 μm to 1000 μm;
• base (B1-1):
• a resin acid selected from rosin, dammar resin, and tall oil fatty acids, or a salt thereof;
• base (B2-1):
• a fatty acid selected from capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, behenic acid, and lignoceric acid, or a salt thereof;
• base (B2-2):
• an alcohol selected from decyl alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol;
• base (B2-3):
• a sulfate selected from lauryl sulfate, tetradecyl sulfate, and hexadecyl sulfate, or a salt thereof;
• base (B2-4):
• an amine selected from dodecylamine, tetradecylamine, and stearylamine;
• base (B3-1):
• a polyhydric alcohol selected from glycerin, polyglycerins, and polyvinyl alcohols having a weight average molecular weight of 30,000 or less;
• and
• base (B3-2):
• a polycarboxylic acid selected from polyacrylic acids having a weight average molecular weight of 30,000 or less and carboxymethyl cellulose having a weight average molecular weight of 30,000 or less, or a salt thereof.