Abstract: There are provided an antidesiccant containing a nucleic acid as an active ingredient which codes for a heat shock protein originating from a salt tolerant cyanobacteria, an antidesiccant containing a nucleic acid which codes for a protein selected from a protein/enzyme relating to a photonic synthesis control, a protein/enzyme controlling the size of a plant body, a protein/enzyme promoting extension of a root, a protein/enzyme promoting growth of a plant body, and a protein/enzyme improving the stability of an RNA, or containing the antisense sequence thereof, a method of using the antidesiccant for making photonic synthesis more efficient, and a transpiration suppression method for a plant.