Transcript Determination of Alkalinity Toxicity Limits of Selected

Determination of Alkalinity
Toxicity Limits of Selected
Greenhouse Ornamental Plants
Luis A. Valdez-A. and David Wm. Reed
Dept. of Horticultural Sciences
Texas A&M University
Alkalinity
• Concentration of soluble alkali
• Alkali have capacity to neutralize acids
• Major contributors:
• HCO3• CO32-
• Minor contributors:
• OH-, NH3
• Phosphates, Silicates, Borates
Buffer Capacity
Capacity to resist sudden changes in pH
CO2
HCO3OH-
H+
H+
OH-
H2CO3
H+
H+
H2O
Effect of pH on Activity of Nutrients
Lindsay, 1981
Alkalinity-induced
Fe Deficiency
Whipker et al., 2001
Objectives
• Provide information about the limits of
tolerance to alkalinity
• Determine the effects of HCO3- in irrigation
water on the growth of selected greenhouse
ornamental plants
• Determine the mechanisms of tolerance to
alkalinity
Experiment 1:
Tolerance to Alkalinity on
Selected Greenhouse Crops
Materials and Methods
• Species: Chrysanthemum ‘Miramar’
Rosa ‘Pink Cupido’
C. roseus ‘Apricot Delight’
H. rosa-sinensis ‘Mango Breeze’
H. rosa-sinensis ‘Bimini Breeze’
Treatment
Solution pH
Control
NaHCO3
mg.L-1
-
2.5 mM
153
8.29
5 mM
305
8.48
7.5 mM
458
8.61
10 mM
610
8.65
7.18
Rose
0 mM
Chrysanthemum
2.5 mM
7.5 mM
5 mM
10 mM
0 mM
2.5 mM
0 mM
7.5 mM
10 mM
5 mM
2.5 mM
7.5 mM
5 mM
10 mM
Vinca
0 mM
5 mM
2.5 mM
7.5 mM
10 mM
Hibiscus ‘Mango Breeze’
5 mM
2.5 mM
0 mM
7.5 mM
10 mM
Hibiscus ‘Bimini Breeze’
% Change
Rose
10
NS
*
*
*
0
-10
NS
-30
-50
*
*
Shoot dry mass
SPAD index
*
-70
0
2.5
5
NaHCO3 (mM)
7.5
10
Shoot dry mass (g)
Rose
SPAD index
50
40
30
20
10
Y=45.3-6.01X+0.40X2 R2=0.86
16
14
12
10
8
6
4
2
Y=12.4-0.61X R2=0.94
0
0
0
2
4
6
8
10
0
NaHCO3 (mM)
2
4
6
8
10
% Change
Chrysanthemum
20
0
NS
NS
NS
NS
NS
-20
*
-40
*
-60
Shoot dry mass
SPAD index
*
-80
0
2.5
5
7.5
NaHCO3 (mM)
10
Chrysanthemum
Shoot dry mass (g)
70
SPAD index
60
50
40
30
20
10
Y=62.8-0.76X-0.38X2 R2=0.99
20
16
12
8
4
Y=17.6+ 0.20X R2=0.87
0
0
0
2
4
6
8
10
0
NaHCO3 (mM)
2
4
6
8
10
% Change
Vinca
10
NS
0
NS
NS
NS
NS
NS
-10
*
-30
-50
*
Shoot dry mass
SPAD index
-70
0
2.5
5
NaHCO3 (mM)
7.5
10
Vinca
Shoot dry mass (g)
SPAD index
50
40
30
20
10
Y=45.3-6.01X+0.40X2 R2=0.86
0
12
10
8
6
4
2
Y=8.79-0.14X R2=0.32
0
0
2
4
6
8
10
0
NaHCO3 (mM)
2
4
6
8
10
% Change
Hibiscus ‘Mango Breeze’
*
20
NS
0
*
NS
-20
-40
*
*
*
Shoot dry mass
SPAD index
*
-60
0
2.5
5
NaHCO3 (mM)
7.5
10
% Change
Hibiscus ‘Bimini Breeze’
20
NS
NS
NS
NS
0
NS
NS
*
-20
*
-40
Shoot dry mass
SPAD index
-60
0
2.5
5
7.5
NaHCO3 (mM)
10
SPAD index
60
Y=55.0-1.30X R2=0.96
50
40
Y=52.2-2.50X R2=0.95
30
20
10
Bimini Breeze
Mango Breeze
0
Shoot dry mass (g)
Hibiscus
12
Y=8.92-0.05X R2=0.20
10
8
Y=8.16-0.40X R2=0.93
6
4
2
Bimini Breeze
Mango Breeze
0
0
2
4
6
8
10
0
NaHCO3 (mM)
2
4
6
8
10
% Shoot Mass Decrease as a Function of
NaHCO3 Concentration
Rose
Shoot
Mass
Decrease
Mum
Vinca
Hibiscus Hibiscus
‘Mango ‘Bimini
Breeze’ Breeze’
Predicted mM NaHCO3
10%
2.0
-*
-*
6.4
-*
20%
4.0
-
-
7.9
-
30%
6.0
-
-
9.0
-
40%
8.0
-
-
9.9
-
*NS growth reduction up to 10 mM NaHCO3 tested
% SPAD Index Decrease as a Function of
NaHCO3 Concentration
Rose
SPAD
Index
decrease
Mum
Vinca
Hibiscus Hibiscus
‘Mango ‘Bimini
Breeze’ Breeze’
Predicted mM NaHCO3
10%
0.8
3.2
6.0
2.1
4.2
20%
1.7
4.8
7.4
4.2
8.5
30%
2.8
6.1
8.4
6.3
12.7
40%
4.2
7.2
9.3
8.4
16.8
Experiment 2:
Mechanisms of Tolerance
to Alkalinity of
Hibiscus
Materials and Methods
•
Cultivars
• ‘Bimini Breeze’
• ‘Carolina Breeze’
• Growing Medium pH
• Fe-Reductase Assay
• Rosenfield et al., 1991
10
pH
9
Growing Medium pH
Bottom Container Layer
Carolina Breeze
Bimini Breeze
8
7
6
5
4
0
2.5
5
7.5
NaHCO3 (mM)
10
Iron Reductase Activity
(µM Fe3+.g-1.h-1.x10-3)
12
Bimini Breeze
Carolina Breeze
10
c
8
a
b
b
6
ab
a
4
a
b
2
b
b
0
0
2
4
6
8
NaHCO3 (mM)
10
Conclusions
• Vinca>‘Bimini Breeze’>Mums>‘Mango Breeze’>Rose
6.0 mM
4.2 mM
3.2 mM
2.1 mM
0.8 mM
• ‘Bimini Breeze’ exhibits
– a higher acidification of the growing medium
– a higher Fe-reductase activity