Hydraulic contribution in cell elongation of tissue-cultured plants: growth retardation induced by osmotic and temperature stresses and addition of 2,4-dichlorophenoxyacetic acid and benzylaminopurine

This work was undertaken to determine the growth parameters of Lockhart's e quation for finding which component was predominantly contributing to the c ell expansion rates of plants subjected to environmental stresses under tis sue-culture conditions. Embryos isolated from soybean (Glycine max [L.] Mer r.) and kidney bean (Phaseolus vulgaris L.) seeds were grown under tissue-c ulture conditions. The water potential of culture media ranged from -0.02 t o -0.94 MPa so that nutrient deficiency and salt stress conditions could be applied. Additionally, the temperature of culture conditions was set from 10 to 40 degrees C to apply low-temperature and high-temperature stresses o n plants grown at the optimum concentration of culture medium. Cell expansi on could be inhibited completely by adding 2,4-dichlorophenoxyacetic acid a nd benzylaminopurine to culture media to form callus tissue. The sizes of t he water potential gradient between the water source and elongating cells c orrelated with the speed of growth rates under nutrient deficiency, salt st ress, growth retardation induced by plant hormones, low-temperature and hig h-temperature conditions in the present study, indicating that cell expansi on rates were mainly associated with how much water could be absorbed by el ongating cells regardless of the kinds of environmental stress conditions a pplied.