The impact of sub and supra optimal potassium supply on abiotic and biotic stress in okra
Potassium is essential for healthy plant growth and development and has been known to ameliorate stress effects in plants. The effect of potassium supply on abiotic and biotic stress was studied in okra plants grown in cell packs and large containers (1.29L) under six K concentrations (1, 2, 4, 6, 8, and 12 mM) in a modified Hoagland solution. The study consisted of four experiments. Experiment-1 was to study K impact on seedlings. Experiment 1.1 and 1.2 studied the effect of K supply on water stress and powdery mildew disease. In Experiment-2, the effect of K supply on plant growth, fruit yield, ion leakage, and transpiration rate were studied. Results showed that K supply did not significantly affect vegetative growth of okra in cell packs under normal water availability as there were no significant differences in shoot and fruit dry weight, or plant height among treatments. SPAD value increased with an increase in K supply up to 12 mM, while visual symptoms of K deficiency and powdery mildew declined with increasing K supply, from 1 to 12 mM. Under water stress conditions, plants supplied with 8 and 12 mM K retained moisture longer in the substrate, with 12 mM K supplied plants having a lower percentage of wilted plants. The percentage of plants with aborting fruits and shrunken stems, due to severe water stress decreased to 0% as K supply increased to 12 mM. Moreover, 6 mM K supplied plants had the highest percentage of wilted leaf recovery (78%) and the highest leaf number per plant with seven leaves. Shoot fresh and dry weights were highest at 6 and 12 mM K supply. For okra growing in 1.29 L pots, K supply did not significantly affect SPAD value, leaf number, fruit yield, total ions leaked or transpiration rate. The percentage of plants with powdery mildew declined to 0% as K supply increased to 6 and12 mM. Substrate EC increased with an increase in K supply. The 12 mM K supplied plants had a significantly lower fresh and dry weight than treatments supplied with < 12 mM K. Plants supplied with 1 mM K had the highest shoot dry weight, though not significantly greater than at 6 mM K. The essentiality of K is critical more so under abiotic and biotic stress conditions (water stress, powdery mildew, K deficiency). A K supply range of 6 to 12 mM may be required to sustain normal growth under these conditions.
"The impact of sub and supra optimal potassium supply on abiotic and biotic stress in okra"
ETD Collection for Tennessee State University.