Use of Mixture Experiments to Determine the Effect of Counter- cations of HCO 3 - on Bean (Phaseolus vulgaris L.) ‘Poncho” in Hydroponics Luis A. Valdez-A. and David Wm. Reed Dept. of Horticultural Sciences Texas A&M University

Bicarbonate Major contributor to alkalinity Major contributor to alkalinity  HCO 3 -  CO 3 2- Minor contributors: Minor contributors:  OH -, NH 3  Phosphates, Silicates, Borates Alkalinity: Concentration of soluble alkali with capacity to neutralize acids Alkalinity: Concentration of soluble alkali with capacity to neutralize acids pH increase pH increase Micronutrients solubility decrease Micronutrients solubility decrease

Alkalinity-induced Fe Deficiency Whipker et al., 2001

Impossible to Study HCO 3 - Alone HCO 3 - Na + Ca ++ K+K+ Li + Rb + Mg ++ NH 4 + Cs +

Mixture Experiments 2 or more Components are mixed 2 or more Components are mixed Rb + + K + + Na + The total concentration is held fixed The total concentration is held fixed Rb + + K + + Na + = 7.5 m M Rb + + K + + Na + = 7.5 m M Mixture: resulting of mixing components at different proportions Mixture: resulting of mixing components at different proportions Rb + : K + : Na + 1/3 : 1/3 : 1/3 1/3 : 1/3 : 1/3 Mixture Amount Experiment: Mixture Amount Experiment: Rb + + K + + Na + =7.5 m M Rb + + K + + Na + =7.5 m M Rb + + K + + Na + =2.5 m M Rb + + K + + Na + =2.5 m M

½:½:0 0:½:½ 2/3:1/6:1/6 1/6:2/3:1/6 1/6:1/6:2/3 1/3:1/3:1/3 Pure blends Tertiary blends Binary blends Rb + 1:0:0 K + 0:1:0 Na + 0:0:1 Rb + K + Na + 1 : 0 : 0 ½:0:½

Objectives Determine the effect of some counter- cations of HCO 3 - on the response of bean plants to HCO 3 - Determine the effect of some counter- cations of HCO 3 - on the response of bean plants to HCO 3 - Separate the effect of the counter-cation from the effect of HCO 3 - Separate the effect of the counter-cation from the effect of HCO 3 -

Materials and Methods Phaseolus vulgaris ‘Poncho’ Phaseolus vulgaris ‘Poncho’ Seeds germinated at 28 0 C Seeds germinated at 28 0 C Hydroponics Hydroponics –7 days establishing period –21 day under treatment

Mixture-Amount Experiment Effect of Mixtures of Rb +, K +, and Na +, on the Response of Bean Plants to HCO 3 -

K + 0 : 7.5 : 0 Rb : 0 : 0 Na + 0 : 0 : : 3.75 : 0 0 : 3.75 : : 1.25 : : 5 : : 1.25 : : 2.5 : : 0 : HCO 3 - Total Concentration = 7.5 mM

K + 0 : 7.5 : 0 Rb : 0 : 0 Na + 0 : 0 : : 3.75 : 0 0 : 3.75 : : 1.25 : : 5 : : 1.25 : : 2.5 : : 0 : HCO 3 -

Na + 0 HCO 3 - K+K+ Rb +

Na HCO 3 - K+K+ Rb +

Shoot Dry Mass O HCO HCO 3 - Shoot Dry Mass (g)

Shoot Dry Mass Na + tox./K + def.=-19% HCO 3 - effect=-15% Shoot Dry Mass (g)

Shoot Dry Mass Rb + tox./K + def.=-30% HCO 3 - effect=-18% Shoot Dry Mass (g)

LEAF TISSUE K + % m M HCO Rb + Na + K+K+

Shoot Dry Mass Rb + +Na + toxicity=-16% HCO 3 - =-22% Shoot Dry Mass (g)

Effect of Binary Mixtures of K + and Na + on the Response of Bean Plants to HCO 3 - Mixture-Amount Binary Experiment

K : 0 Na + 0 : 2.5 K + Na : 1.25 K + Na : 0.62 K + Na : 1.88 K : 0 K + Na : 0.62 K + Na : 1.25 K + Na : 1.88 Na + 0 : HCO HCO 3 -

K + 5 : 0 Na + 0 : 5 K + Na : 2.5 K + Na : 1.25 K + Na : 3.75 K + 5 : 0 K + Na : 1.25 K + Na : 2.5 K + Na : 3.75 Na + 0 : 5 5 HCO HCO 3 -

K : 0 Na + 0 : 7.5 K + Na : 3.75 K + Na : 3.75 K + Na : 3.75 K : 0 K + Na : 3.75 K + Na : 3.75 K + Na : 3.75 Na + 0 : HCO HCO 3 -

0m M HCO m M HCO 3 - K + :Na + 1:0 0.75: : :0.75 0:1 4.37g4.75g4.73g3.63g2.36g 3.02g3.30g3.43g3.01g2.12g

2.5 HCO m M total mixture 0 HCO 3 - Proportion of K + and Na + Shoot Dry Mass Shoot Dry Mass Na + =-19% HCO 3 - =-19% Shoot Dry Mass (g) Na + K+K+

K + :Na + 1:0 0.75: : :0.75 0:1 0m M HCO 3 - 5m M HCO g 4.15g 4.86g4.29g2.45g 2.79g2.87g 3.34g2.55g1.62g

5 m M total mixture 0 HCO HCO 3 - Proportion of K + and Na + Shoot Dry Mass Na + =-17% HCO 3 - =-24% Shoot Dry Mass (g) Na + K+K+

0m M HCO m M HCO 3 - K + :Na + 1:0 0.75: : :0.75 0:1 5.18g 4.31g 4.58g 2.45g 3.15g 2.59g2.86g2.20g2.78g2.15g

7.5 m M total mixture 0 HCO HCO 3 - Proportion of K + and Na + Shoot Dry Mass Na + =-41% HCO 3 - =-15% Shoot Dry Mass (g) Na + K+K

Na + (m M ) HCO 3 - (m M ) Bicarbonate Effect Sodium Effect Percentage Growth Reduction due to Counter-Cation and HCO 3 - Average=18% % Shoot Dry Mass Decrease

Conclusions The effect of both Na + and HCO 3 - is approximately the same at normal concentrations The effect of both Na + and HCO 3 - is approximately the same at normal concentrations At high concentrations, the Na + toxicity effect is much higher than that of HCO 3 - At high concentrations, the Na + toxicity effect is much higher than that of HCO 3 -