Plants from the
Fruits and vegetables have varying levels of phytonutrients, in addition to vitamins and minerals. Two important classes of phytonutrients are carotenoid and chlorophyll pigments. The primary carotenoids found in leaf tissue of most plant species include zeaxanthin, antheraxanthin, violaxanthin, lutein,
The absorption of light by chlorophyll and antenna pigments and the transfer of excitation energy to the reaction centers of PSII and PSI are the initial steps in photosynthesis. The photosynthetic apparatus has the ability to react to many different environmental stimuli, especially changes in light intensity. Under conditions of high light stress, photosynthetic systems are saturated, and excess energy needs to be diverted to avoid potential damage [
Higher amounts of UV-A (380–320 nm) and UV-B radiation (280–320 nm) may influence the accumulation of plant compounds used to combat light stress. Carotenoid metabolites not only protect plants from excess UV radiation but also can protect humans from UV radiation when translocated to subdermal skin tissues [
On December 16, 2008, seeds of 16 different
Supplemental UV-B radiation (313 nm) was provided by banks of commercially available UV-B 313 lamps (Q-Panel Lab Products, Cleveland, OH, USA), and treatment began on January 27, 2009 delivering 7.0
On March 3, 2009, all of the bunching onion cultigens were harvested. Six plants were harvested from each replication. Fresh weights and plant heights were taken and averaged for each replication. One measure of
Tissue pigments were extracted according to Kopsell et al. [
An Agilent 1200 series HPLC unit with a photodiode array detector (Agilent Technologies, Palo Alto, CA, USA) was used for pigment separation (Figure
HPLC chromatogram of
Statistical analyses were completed using the GLM procedure of SAS (v. 9.1, SAS Institute, Cary, NC, USA). Cultigen means within each treatment were separated by least significant difference (LSD) at
Significant differences were found among cultigens (
Mean valuesa for shoot tissue height (cm) and fresh biomass (g) for
Cultigen | Shoot tissue height (cm) | Shoot tissue fresh biomass (g) | ||||
---|---|---|---|---|---|---|
UV-B | Control | Pr > |
UV-B | Control | Pr > |
|
Deep Purple | 44.71 ± 5.49 | 45.19 ± 4.52 | ns | 64.54 ± 17.02 | 97.80 ± 17.44 |
|
Evergreen Hardy White | 39.11 ± 1.96 | 41.05 ± 5.38 | ns | 38.65 ± 7.80 | 70.78 ± 8.08 | ns |
Feast | 38.58 ± 3.24 | 39.96 ± 2.40 | ns | 48.79 ± 15.99 | 90.46 ± 13.85 |
|
GA-C 76 | 38.82 ± 1.91 | 44.13 ± 3.70 |
|
41.90 ± 2.66 | 73.00 ± 15.53 |
|
Ishikura improved F1 | 39.63 ± 1.12 | 41.17 ± 3.13 | ns | 54.93 ± 9.22 | 99.80 ± 9.47 |
|
Improved Beltsville Bunching | 44.26 ± 1.69 | 48.06 ± 2.19 | ns | 76.86 ± 9.82 | 110.42 ± 19.39 |
|
Jionji Negi | 36.20 ± 1.82 | 38.63 ± 1.54 | ns | 38.05 ± 4.73 | 62.04 ± 8.23 |
|
Long White Bunching | 49.68 ± 2.09 | 50.38 ± 4.62 | ns | 74.07 ± 8.73 | 116.01 ± 20.24 |
|
Parade | 42.13 ± 2.60 | 36.03 ± 9.40 | ns | 53.89 ± 10.73 | 90.81 ± 16.87 |
|
Performer | 39.37 ± 2.36 | 39.42 ± 3.10 | ns | 54.74 ± 11.08 | 86.25 ± 16.66 |
|
Pesoenyj | 39.44 ± 4.23 | 44.54 ± 4.03 | ns | 29.22 ± 9.30 | 58.76 ± 6.37 |
|
Shounan | 36.72 ± 3.02 | 37.14 ± 2.54 | ns | 39.17 ± 3.56 | 63.32 ± 4.02 |
|
White Spear | 40.06 ± 2.79 | 42.42 ± 1.72 | ns | 53.16 ± 14.41 | 87.42 ± 10.58 |
|
Zhang Qui Da Cong | 36.62 ± 2.88 | 37.87 ± 3.80 | ns | 53.57 ± 19.51 | 84.72 ± 16.67 | ns |
274254-05GI | 42.48 ± 1.86 | 43.79 ± 4.40 | ns | 47.63 ± 4.34 | 84.65 ± 6.98 |
|
G 30393-06GI | 36.62 ± 3.40 | 35.67 ± 1.31 | ns | 50.96 ± 8.63 | 81.69 ± 12.01 |
|
|
5.77 | 5.80 | 10.72 | 19.33 |
aComposition of
No carotenoid pigments were measured in the pseudostem tissues of any of the bunching onion cultigens (Figure
Mean valuesa for shoot tissue zeaxanthin, violaxanthin, and antheraxanthin (mg/100 g fresh mass) for
Cultigen | Zeaxanthin | Violaxanthin | Antheraxanthin | ||||||
---|---|---|---|---|---|---|---|---|---|
UV-B | Control | Pr > |
UV-B | Control | Pr > |
UV-B | Control | Pr > |
|
mg/100 g fresh mass | |||||||||
| |||||||||
Deep Purple | 0.08 ± 0.02 | 0.10 ± 0.03 | ns | 1.25 ± 0.36 | 0.88 ± 0.42 | ns | 1.07 ± 0.31 | 0.78 ± 0.23 | ns |
Evergreen Hardy White | 0.10 ± 0.03 | 0.07 ± 0.02 | ns | 1.73 ± 0.61 | 1.20 ± 0.25 | ns | 1.03 ± 0.18 | 0.78 ± 0.14 | ns |
Feast | 0.11 ± 0.01 | 0.07 ± 0.01 |
|
1.35 ± 0.82 | 0.66 ± 0.58 | ns | 1.15 ± 0.27 | 0.92 ± 0.19 | ns |
GA-C 76 | 0.12 ± 0.02 | 0.08 ± 0.02 | ns | 2.04 ± 0.19 | 1.34 ± 0.20 |
|
1.92 ± 0.65 | 1.27 ± 0.47 | ns |
Ishikura Improved F1 | 0.10 ± 0.05 | 0.09 ± 0.02 | ns | 1.75 ± 0.94 | 1.10 ± 0.38 | ns | 0.81 ± 0.50 | 0.59 ± 0.13 | ns |
Improved Beltsville Bunching | 0.16 ± 0.02 | 0.15 ± 0.04 | ns | 1.62 ± 0.54 | 1.25 ± 0.14 | ns | 0.99 ± 0.38 | 0.72 ± 0.21 | ns |
Jionji Negi | 0.12 ± 0.06 | 0.13 ± 0.03 | ns | 1.54 ± 0.25 | 1.51 ± 0.35 | ns | 1.20 ± 0.25 | 0.78 ± 0.50 | ns |
Long White Bunching | 0.12 ± 0.03 | 0.11 ± 0.03 | ns | 0.89 ± 0.18 | 0.81 ± 0.42 | ns | 0.82 ± 0.13 | 0.89 ± 0.14 | ns |
Parade | 0.10 ± 0.02 | 0.11 ± 0.02 | ns | 1.23 ± 0.50 | 1.02 ± 0.61 | ns | 0.86 ± 0.16 | 0.79 ± 0.24 | ns |
Performer | 0.09 ± 0.02 | 0.10 ± 0.02 | ns | 0.59 ± 0.52 | 1.45 ± 0.60 | ns | 0.87 ± 0.06 | 0.85 ± 0.32 | ns |
Pesoenyj | 0.12 ± 0.03 | 0.19 ± 0.06 | ns | 1.93 ± 0.33 | 2.35 ± 0.82 | ns | 1.38 ± 0.30 | 1.35 ± 0.52 | ns |
Shounan | 0.13 ± 0.05 | 0.09 ± 0.01 | ns | 1.87 ± 0.81 | 1.04 ± 0.36 | ns | 1.18 ± 0.40 | 0.63 ± 0.30 | ns |
White Spear | 0.08 ± 0.02 | 0.08 ± 0.03 | ns | 1.00 ± 0.60 | 0.77 ± 0.47 | ns | 0.74 ± 0.13 | 0.60 ± 0.09 | ns |
Zhang Qui Da Cong | 0.11 ± 0.04 | 0.12 ± 0.02 | ns | 1.29 ± 0.48 | 1.30 ± 0.41 | ns | 0.81 ± 0.30 | 0.74 ± 0.06 | ns |
274254-05GI | 0.13 ± 0.04 | 0.15 ± 0.03 | ns | 1.64 ± 0.42 | 1.27 ± 0.52 | ns | 0.79 ± 0.14 | 0.71 ± 0.33 | ns |
G 30393-06GI | 0.13 ± 0.03 | 0.08 ± 0.02 |
|
0.60 ± 0.51 | 0.50 ± 0.43 | ns | 1.07 ± 0.35 | 0.67 ± 0.14 | ns |
|
ns | 0.04 | 0.74 | 0.70 | 0.44 | 0.44 |
aComposition of
Shoot tissue violaxanthin responded significantly to both UV-B radiation treatment (
Antheraxanthin, the intermediate compound in xanthophyll cycle, responded significantly to changes in UV-B radiation treatments (
Neoxanthin concentrations responded significantly to UV-B radiation treatment (
Mean valuesa for shoot tissue neoxanthin, lutein, and
Cultigen | Neoxanthin | Lutein |
| ||||||
---|---|---|---|---|---|---|---|---|---|
UV-B | Control | Pr > |
UV-B | Control | Pr > |
UV-B | Control | Pr > |
|
mg/100 g fresh mass | |||||||||
| |||||||||
Deep Purple | 0.73 ± 0.51 | 1.04 ± 0.59 | ns | 5.04 ± 1.48 | 5.38 ± 0.73 | ns | 1.07 ± 0.81 | 1.09 ± 0.30 | ns |
Evergreen Hardy White | 0.74 ± 0.47 | 0.40 ± 0.18 | ns | 7.10 ± 2.86 | 5.10 ± 1.49 | ns | 0.88 ± 0.71 | 0.64 ± 0.23 | ns |
Feast | 2.09 ± 0.48 | 0.79 ± 0.57 |
|
7.66 ± 0.90 | 4.11 ± 0.54 |
|
1.85 ± 0.85 | 1.04 ± 0.74 | ns |
GA-C 76 | 1.53 ± 0.32 | 0.66 ± 0.18 |
|
7.66 ± 0.38 | 5.57 ± 0.67 |
|
1.48 ± 0.27 | 1.17 ± 0.09 | ns |
Ishikura Improved F1 | 0.63 ± 0.43 | 0.63 ± 0.30 | ns | 6.35 ± 3.18 | 4.80 ± 1.20 | ns | 2.20 ± 2.59 | 0.78 ± 0.41 | ns |
Improved Beltsville Bunching | 0.82 ± 0.89 | 0.60 ± 0.16 | ns | 6.95 ± 1.34 | 5.62 ± 0.65 | ns | 1.64 ± 0.95 | 1.39 ± 0.30 | ns |
Jionji Negi | 0.92 ± 0.25 | 0.91 ± 0.36 | ns | 7.35 ± 1.65 | 6.21 ± 1.49 | ns | 1.74 ± 1.20 | 2.29 ± 1.32 | ns |
Long White Bunching | 1.76 ± 0.26 | 1.47 ± 0.35 | ns | 6.00 ± 0.58 | 5.05 ± 1.17 | ns | 1.69 ± 0.29 | 1.94 ± 0.56 | ns |
Parade | 1.46 ± 0.81 | 0.87 ± 0.36 | ns | 6.36 ± 1.17 | 6.04 ± 1.47 | ns | 1.26 ± 0.14 | 2.54 ± 1.23 | ns |
Performer | 1.14 ± 0.90 | 0.75 ± 0.47 | ns | 6.33 ± 0.96 | 5.60 ± 2.36 | ns | 1.28 ± 0.48 | 2.38 ± 1.65 | ns |
Pesoenyj | 1.03 ± 0.19 | 1.96 ± 0.78 | ns | 8.01 ± 1.21 | 9.23 ± 2.59 | ns | 1.87 ± 0.20 | 3.45 ± 2.39 | ns |
Shounan | 1.32 ± 0.71 | 0.54 ± 0.32 | ns | 7.66 ± 2.83 | 5.03 ± 1.26 | ns | 2.80 ± 1.46 | 1.10 ± 0.54 | ns |
White Spear | 1.21 ± 0.62 | 0.93 ± 0.63 | ns | 6.08 ± 0.94 | 4.70 ± 1.37 | ns | 1.49 ± 0.51 | 1.08 ± 0.60 | ns |
Zhang Qui Da Cong | 0.75 ± 0.42 | 0.65 ± 0.29 | ns | 5.65 ± 1.44 | 5.31 ± 1.47 | ns | 1.05 ± 0.24 | 1.20 ± 0.57 | ns |
274254-05GI | 0.84 ± 0.37 | 0.72 ± 0.45 | ns | 6.18 ± 0.79 | 5.33 ± 1.82 | ns | 1.81 ± 0.86 | 1.86 ± 1.57 | ns |
G 30393-06GI | 1.86 ± 0.44 | 0.85 ± 0.62 |
|
6.02 ± 1.18 | 4.42 ± 0.69 | ns | 1.86 ± 0.77 | 1.28 ± 0.67 | ns |
|
0.78 | 0.67 | ns | 2.14 | ns | 1.54 |
aComposition of
The bunching onions showed significant changes in lutein in response to UV-B treatment (
Concentrations of
The xanthophyll cycle pigments (zeaxanthin, antheraxanthin, and violaxanthin) are important for the dissipation of excess absorbed light, performed almost exclusively by ZEA. Photosynthetic rates are reduced under many environmental stressors, which increase the need for dissipation of excess absorbed light energy [
Mean valuesa for the ratio of zeaxanthin + antheraxanthin to zeaxanthin + antheraxanthin + violaxanthin (Z + A/A + Z + V) and the ratio of chlorophyll
Cultigen | Z + A/A + Z + V | Chlorophyll |
||||
---|---|---|---|---|---|---|
UV-B | Control | Pr > |
UV-B | Control | Pr > |
|
Deep Purple | 0.48 ± 0.01 | 0.51 ± 0.19 | ns | 1.25 ± 0.90 | 1.50 ± 0.23 | ns |
Evergreen Hardy White | 0.41 ± 0.06 | 0.41 ± 0.01 | ns | 1.15 ± 0.56 | 0.91 ± 0.16 | ns |
Feast | 0.51 ± 0.16 | 0.65 ± 0.21 | ns | 2.14 ± 0.43 | 1.07 ± 0.63 |
|
GA-C 76 | 0.49 ± 0.07 | 0.49 ± 0.10 | ns | 1.58 ± 0.18 | 0.93 ± 0.51 | ns |
Ishikura Improved F1 | 0.34 ± 0.03 | 0.40 ± 0.08 | ns | 1.69 ± 1.06 | 1.45 ± 0.70 | ns |
Improved Beltsville Bunching | 0.41 ± 0.03 | 0.41 ± 0.07 | ns | 1.04 ± 0.92 | 1.29 ± 0.50 | ns |
Jionji Negi | 0.46 ± 0.07 | 0.35 ± 0.15 | ns | 1.85 ± 0.70 | 2.21 ± 0.50 | ns |
Long White Bunching | 0.52 ± 0.04 | 0.58 ± 0.17 | ns | 1.86 ± 0.06 | 2.25 ± 0.68 | ns |
Parade | 0.45 ± 0.10 | 0.50 ± 0.24 | ns | 1.77 ± 0.33 | 2.16 ± 0.48 | ns |
Performer | 0.66 ± 0.17 | 0.40 ± 0.02 | ns | 1.60 ± 0.11 | 2.07 ± 1.19 | ns |
Pesoenyj | 0.44 ± 0.03 | 0.39 ± 0.01 |
|
1.40 ± 0.42 | 1.95 ± 0.80 | ns |
Shounan | 0.42 ± 0.03 | 0.40 ± 0.03 | ns | 1.78 ± 0.52 | 1.08 ± 0.53 | ns |
White Spear | 0.50 ± 0.21 | 0.51 ± 0.22 | ns | 1.46 ± 0.42 | 1.08 ± 0.62 | ns |
Zhang Qui Da Cong | 0.42 ± 0.05 | 0.41 ± 0.08 | ns | 1.11 ± 0.50 | 1.32 ± 0.46 | ns |
274254-05GI | 0.36 ± 0.06 | 0.40 ± 0.00 | ns | 1.80 ± 0.71 | 2.14 ± 0.81 | ns |
G 30393-06GI | 0.69 ± 0.20 | 0.55 ± 0.12 | ns | 1.84 ± 0.31 | 1.32 ± 0.64 | ns |
|
0.15 | 0.20 | ns | 0.96 |
aComposition of
Kopsell et al. [
Epidemiological data supports the positive association between increased dietary intake of plant foods high in carotenoids and greater carotenoid tissue concentrations with lower risks of certain chronic diseases. Many of these disease suppressing abilities can be attributed to the antioxidant properties of carotenoids. One of the most important physiological functions of carotenoids in human nutrition is as vitamin A precursors. Provitamin A carotenoid compounds (
No chlorophyll pigments were measured in the pseudostem tissues of any of the bunching onion cultigens (Figure
Mean valuesa for shoot tissue chlorophyll
Cultigen | Chlorophyll |
Chlorophyll |
Total chlorophyll | ||||||
---|---|---|---|---|---|---|---|---|---|
UV-B | Control | Pr > |
UV-B | Control | Pr > |
UV-B | Control | Pr > |
|
mg/100 g fresh mass | |||||||||
| |||||||||
Deep Purple | 27.8 ± 22.1 | 25.3 ± 5.6 | ns | 20.6 ± 4.4 | 16.9 ± 2.4 | ns | 48.3 ± 25.6 | 42.1 ± 7.5 | ns |
Evergreen Hardy White | 31.4 ± 21.1 | 16.5 ± 3.2 | ns | 25.5 ± 5.1 | 18.2 ± 0.7 | ns | 56.9 ± 26.1 | 34.7 ± 3.5 | ns |
Feast | 59.6 ± 20.3 | 19.0 ± 10.5 |
|
27.3 ± 4.0 | 17.7 ± 1.9 |
|
86.8 ± 24.3 | 36.7 ± 11.0 |
|
GA-C 76 | 47.0 ± 16.4 | 17.2 ± 10.6 | ns | 29.2 ± 7.1 | 18.1 ± 1.3 |
|
76.2 ± 23.3 | 35.4 ± 11.5 |
|
Ishikura Improved F1 | 49.9 ± 53.6 | 23.1 ± 5.9 | ns | 25.6 ± 11.6 | 17.6 ± 4.7 | ns | 74.5 ± 65.1 | 40.7 ± 2.6 | ns |
Improved Beltsville Bunching | 23.9 ± 28.4 | 20.6 ± 8.9 | ns | 18.5 ± 7.6 | 15.8 ± 1.0 | ns | 42.4 ± 36.0 | 36.1 ± 9.8 | ns |
Jionji Negi | 48.3 ± 23.4 | 47.2 ± 18.9 | ns | 25.5 ± 3.1 | 20.9 ± 4.8 | ns | 73.8 ± 26.0 | 68.0 ± 23.4 | ns |
Long White Bunching | 36.9 ± 6.6 | 37.2 ± 7.4 | ns | 19.7 ± 2.8 | 17.1 ± 2.7 | ns | 56.5 ± 9.2 | 54.3 ± 6.3 | ns |
Parade | 38.6 ± 13.2 | 44.4 ± 18.8 | ns | 21.2 ± 4.1 | 19.9 ± 4.4 | ns | 59.8 ± 17.2 | 64.3 ± 23.0 | ns |
Performer | 36.8 ± 3.1 | 49.6 ± 31.9 | ns | 23.0 ± 2.1 | 20.9 ± 7.1 | ns | 59.8 ± 4.8 | 70.5 ± 38.9 | ns |
Pesoenyj | 36.8 ± 10.2 | 63.3 ± 36.9 | ns | 26.3 ± 2.4 | 29.7 ± 8.7 | ns | 26.3 ± 2.4 | 93.0 ± 45.6 | ns |
Shounan | 44.3 ± 24.9 | 20.6 ± 19.1 | ns | 24.3 ± 8.3 | 16.6 ± 7.6 | ns | 68.6 ± 32.6 | 37.2 ± 26.7 | ns |
White Spear | 30.4 ± 9.9 | 18.2 ± 9.6 | ns | 20.8 ± 1.9 | 17.8 ± 1.0 |
|
51.2 ± 10.7 | 35.4 ± 8.9 | ns |
Zhang Qui Da Cong | 25.3 ± 18.3 | 27.3 ± 13.5 | ns | 20.4 ± 7.4 | 19.3 ± 4.2 | ns | 45.6 ± 25.6 | 47.1 ± 17.6 | ns |
274254-05GI | 36.6 ± 23.1 | 40.0 ± 18.1 | ns | 18.9 ± 5.3 | 18.7 ± 4.9 | ns | 55.5 ± 28.3 | 58.6 ± 21.5 | ns |
G 30393-06GI | 39.8 ± 11.3 | 22.6 ± 13.8 | ns | 21.3 ± 4.1 | 17.0 ± 3.7 | ns | 61.1 ± 15.1 | 39.6 ± 16.0 | ns |
|
ns | 26.0 | ns | 6.8 | ns | 31.6 |
aComposition of
The bunching onions showed significant differences in chlorophyll
Concentrations of total chlorophyll (chlorophyll
The ratio of chlorophyll
Photochemical efficiency (
Data from multiple studies demonstrates cultigens within a given plant species can react differently under variable stress conditions. Most often, harsh stress conditions negatively impact plant biomass. In the current study, decreases in bunching onion shoot tissue biomass confirmed that a radiational stress from the UV-B treatment had occurred. The bunching onion cultigens demonstrated genetic variability in response to UV-B radiation (Tables
The authors of the paper do not have a direct financial relation with the commercial identities mentioned in the paper that might lead to conflict of interests.
Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the University of Tennessee Institute of Agriculture. Authors would like to acknowledge funding and support for this work by the University of Tennessee Agricultural Experiment Station.