Applications of xerophytophysiology in plant production - Sorghum plants improved by exposing the mesocotyl as stimulus

Theoretical research shows that plants perceive environmental stimuli, transduce the stimuli as signals to the internals and take regulations in response to the environmental changes. However, very few trials are made to use this theory to crop production. In this research, as a measure of stimulation, mesocotyls and part of the nodal roots of seedlings of sorghum (Sorghum bicolor L. cv. Lucky) were exposed by removing soils away immediately around the base part with the seminal root anchoring in the Sufficiently moist soil. When the treatment of mesocotyl exposition lasted for about 10 days, the exposed part of the roots changed the color from white through purple-red to green and the seedlings became shorter but thicker with leaves shorter, wider and deeper in color, compared with those of control. The top dry mass was depressed but the root dry mass was increased by the treatment. One month after the exposition finished and the base part was covered with soils, the depressed top part exceeded that of control plants. Consequently, the total dry mass and grain yield increased. The promoted growth was associated with the symplastic water compartmenting and leaf turgor maintenance induced by osmotic adjustment during mesocotyl exposing treatment, as shown by the analysis of P-V curve. Analysis of transpiration declining curve showed that the mesocotyl-exposed sorghum plants possessed higher drought resistance ability, as shown by sensitive stomatal response and low cuticular transpiration. It is concluded that exposing the mesocotyl is a good practice to harden the sorghum seedlings and increase plant growth and grain yield on the bases of signal transduction and xerophytophysiology.