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The effect of vanadium on germination and seedling growth of lettuce (Lactuca sativaL. C. V. Salad Bowi )
Department of Biology, Liverpool Polytechnic, Liverpool, U. K.
The Effect of Vanadium on Germination and Seedling Growth of Lettuce (Lactuca sativa L. C. V. SALAD BOWl) N. W.
LEPP
Received December 6, 1976 . Accepted December 22, 1976
Summary The effect of vanadium, applied as VOS0 4 , on germination and subsequent seedling growth of Lettuce has been studied. No differences in germination were observed at any of the applied vanadium concentrations, when compared to a vanadium-free control. Subsequent seedling growth, however, was significantly inhibited by all vanadium treatments. Reductions in shoot growth, root growth and fresh weight were apparent. Similar, but less dramatic effects were observed when 3 day old seedlings were transferred to vanadium enriched media. Key words: vanadium, germination, seedling growth, Lactuca sativa.
Introduction Vanadium is a relatively uncommon constituent of the earth's crust, its frequency being of the same order of magnitude as Cu, Ni, Pb or Zn (BERTRAND, 1960). This author details sources of vanadium in the geosphere; these include petrochemicals, petrochemical-bearing schists and fossil fuels. Vanadium release into the environment comes when fossil fuels and petrochemicals are combusted (ZOLLER, 1971). A recent report (JACKS, 1976) describes the accumulation of vanadium in a semiurban locality in Sweden, and BROSSETT (1976) reports air pollution episodes in the same country where vanadium-rich particulates predominate. In view of the apparent increase of vanadium in the biosphere, the effects of this element on living organisms should be considered. In regard to plants, studies relating to vanadium are sparse and scattered. Vanadium is toxic to plants, when levels of «available» vanadium in soils exceed 20 ppm (CANNON, 1963; NASON and McELROY, 1963). Beneficial responses to lower levels of vanadium have also been reported. ARNON and WESSEL (1953) claim this element is essential for green algae, whilst a beneficial response of mature sugar beets to vanadium is reported by SINGH and WORT (1969). Studies on seed germination are somewhat contradictory. CANNON (1963) found no response of Sorghum, with regard to seed germination and subsequent seedling growth, to 1 ppm vanadium. CATALINA (1966) found stimulation of germination of a range of species in response to vanadium applications of between 1 and 50 ppm. Z. Pjlanzenphysiol. Ed. 83, S. 185-188.1977.
186
N. W.
LEPp
This study also revealed a concomitant increase in activity of various enzymes following vanadium treatment of seeds. The present study was undertaken to provide a clearer insight into the effects of vanadium on seed germination and subsequent seedling growth of Lettuce, with a view to establishing the true status of this element with regard to phytotoxicity. Materials and Methods Seeds of Lactuca sativa L. C. V. SALAD BOWl, obtained from a commercial sou used in all experiments. Batches of 50 seeds were sown on filter paper circles contained in petri dishes, then irrigated with 2 ml of the appropriate solution. Treated seeds were placed in constant illumination at 20°C. Under these conditions, germination occurred within 48 hours. Seedlings were harvested, weighed and measured after 7 days growth. In the transfer experiments, seedlings were germinated in the absence of vanadium, then transferred to appropriate vanadium treatments after 3 days. Such seedlings were harvested after a further 4 days growth. In all experiments, vanadium was supplied as VOS0 4 solution at concentrations between 50 and 0.05 ppm.
Results and Discussion Table 1 illustrates the effect of a range of vanadium concentrations on seed germination and subsequent seedling growth. Several points emerge from these results. First, none of the vanadium treatments significantly altered germination percentage. However, subsequent seedling growth is markedly affected by increasing concentration of vanadium. Fresh weight increases are significantly reduced, and there is a concomitant reduction of root and shoot extension, 86 % reduction of both root and shoot extension is recorded at the highest vanadium concentration (50 ppm). Such quantitative changes were also accompanied by some striking alterations in the morphology of the seedlings. At vanadium concentrations of 5 and 50 ppm,
Table 1: Effect of vanadium on various properties of germinating lettuce seedlings. Germ.
Fresh wt.
50 5 0.5 .05
52 52 51 47
0.23 0.57 0.61 0.66
Control
56
ppmV
%
± ± ± ± 0.92 ±
.03 .09 .04 .08 .12
Root Length
± ± ± ± 37.56 ±
5.14 16.94 23.65 24.91
.95 2.54 3.05 2.08 2.55
(86) (55) (37) (33)
Shoot Length
± ± ± ± 17.2 ±
2.27 5.07 8.31 12.3
0.25 1.23 1.83 1.64
(86) (70) (52) (28)
1.64
germination scored at 72 hours. Remaining measurements made 7 days after sowing. Means ± S. E's (at p ~ 0.05) are given for all germinated seedlings. Fresh weights are given for 10 randomly selected seedlings from each treatment. Figures in brackets refer to % growth reduction (against the control). Fresh weights are given in gms, root and shoot length" in mm.
0/0
z.
Pjlanzenphysiol. Bd. 83, S. 185-188.1977.
Effect of Vanadium on germination
187
marked helicoid orientation of seedlings was obst::rved, showing similarities to those reported by PUERNER and SIEGEL (1972) for cucumber seedlings exposed to high levels of several heavy metals. Roots produced by these plants were branched, and at 50 ppm vanadium, progressive root die-back was noted. This was manifest as the occurrence of necrotic apices, together with the production of numerous peg-like secondary roots. CANNON (1963) reports that morphological symptoms of vanadium toxicity include reddening of young leaves, followed by chlorosis. Seedlings grown in 50 ppm vanadium exhibited a degree of reddening, but no apparent chlorosis. Table 2: Effect of vanadium treatment subsequent to germination on various properties of lettuce seedlings. ppmV 50 5 0.5 0.05 Control Seedlings grown in vanadium solution. Means ± S. E's (at reductions (against given III mm.
Fresh wt.
± ± ± ± 0.178 ±
0.102 0.134 0.154 0.158
.014 .008 .013 .001 .009
Root Length
± ± ± ± 52.9 ± 25.2 34.1 43.9 49.9
5.1 (52) 3.4 (45) 5.6 (27) 5.0 (6) 3.7
Shoot Length
± ± ± ± 22.5 ± 13.7 16.3 19.3 2004
1.04 1.06 1.13 1.19
(46) (32) (16) (8)
.083
distilled water for 72 hours, then 10 uniform seedlings transferred to Measurements made after 4 further days in the respective treatments. p ~ 0.05) given for all seedlings. Figures in brackets refer to Ofo growth the control). Fresh weights are given in gms, root and shoot lengths
Table 2 illustrates the response of seedlings to vanadium application following a period of normal growth. From these results, it can be seen that vanadium still inhibits growth, but to a somewhat lesser extent. The reddening effect at 50 ppm vanadium was again evident, but no other morphological abnormalities were evident. These results provide some evidence as to the phytotoxic potential of vanadium. It is quite clear that levels in excess of 5 ppm applied vanadium can markedly reduce growth of lettuce seedlings and in some cases produce quite distinct morphological changes. It is evident that vanadium can be absorbed by roots [as found by WELCH (1973)], accumulated within these tissues, and may also be transported to the shoot. The mechanism of toxicity is not clear, but two possibilities could exist. Firstly vanadium could be enhancing the activity of various enzymes, particularly those involved in regulating hormone levels. It has been established that copper can affect IAA-oxidase activity (MUKHERJI and DAS GUPTA, 1972; COOMBES et al., 1976); vanadium may have a similar effect. Alternatively vanadium could affect the available calcium status of the seedlings. CANNON (1963) presents evidence for interaction between calcium and vanadium in plant tissues. Vanadium will readily combine with calcium to form insoluble calcium vanadate, deposits of this being observed in roots of naturally calcium-rich plants grown in vanadiumcontaining
z.
Pflanzenphysiol. Bd. 83, S. 185-188. 1977.
188
N. W. LEPP
media. It is possible that growth of seedlings at the higher vanadum treatments is being arrested due to an increase in calcium vanadate formation, with a resultant decrease in calcium available for cell-wall formation. Further work is work is clearly required to resolve the mechanism of vanadium toxicity. The present results serve to highlight the phytotoxic potential of this element, but a re-appraisal of its present status as an environmental contaminant clearly requires a more exhaustive examination. References ARNON, D. ]., and G. WESSEL: Vanadium as an essential element for green plants. Nature. 172, 1040 (1953). BERTRAND, D.: The biogeochemistry of vanadium. In Survey of contemporary knowledge of biogeochemistry. Am. Mus. Nat. History. Bul!. 94, 409-455 (1950). BROSSET, c.: Airborne particles: Black and white episodes. Ambio. 5,157-163. (1976). CANNON, H.: The biogeochemistry of vanadium. Soil Sci. 96, 196-204 (1963). CATALINA, L.: Influence of vanadium on germination. An. Edafo!' Agrobio!. (Madrid). 25, 551-559 (1966). COOMBES, A. ]., N. W. LEPP, and D. A. PHIPPS: The effect of copper on IAA-oxidase activity in root tissue of Barley (Hordeum vulgare L. C. V. ZEZHYR). Z. Pflanzenphysio!. 80,236-242 (1976). JACKS, G.: Vanadium in an area just outside Stockholm. Environ. Pollut. 11, 289-295 (1976). MUKHERJI, S., and B. DAS GUPTA: Characterisation of copper toxicity in lettuce seedlings. Physio!. Plant. 27, 126-129 (1972). NASON, A., and W. D. McELROY: Modes of action of essential mineral elements. In Plant Physiology: A treatise. edit. STEWARD, F. C. 3, 451-536. Academic Press, New York, 1963. PUERNER, N. ]., and S. M. SIEGEL: The effects of mercury compounds on the growth and orientation of cucumber seedlings. Physio!. Plant. 26, 310-312 (1972). SINGH, B. B., and D. ]. WORT: Effect of vanadium on growth, chemical composltlon and and metabolic processes of mature sugar beet (Beta vulgaris L.) plants. P!. Physio!. 44, 1321-1327 (1969). WELCH, R. M.: Vanadium uptake by plants. Absorption kinetics and the effect of pH, metabolic inhibitors and other anions and cations. P!. Physio!. 51, 828-832 (1973). ZOLLER, W. H.: The distribution of vanadium in the atmosphere. Nat. Mag. Am. Chern. Soc. 162,12-17 (1971).
Dr. N. W. LEPP, Department of Biology, Liverpool Polytechnic, Byrom Street, Liverpool L3 3AF, U.K.
Z. P/lanzenphysiol. Bd. 83, S. 185-188.1977.
The Effect of Vanadium on Germination and Seedling Growth of Lettuce (Lactuca sativa L. C. V. SALAD BOWl) N. W.
LEPP
Received December 6, 1976 . Accepted December 22, 1976
Summary The effect of vanadium, applied as VOS0 4 , on germination and subsequent seedling growth of Lettuce has been studied. No differences in germination were observed at any of the applied vanadium concentrations, when compared to a vanadium-free control. Subsequent seedling growth, however, was significantly inhibited by all vanadium treatments. Reductions in shoot growth, root growth and fresh weight were apparent. Similar, but less dramatic effects were observed when 3 day old seedlings were transferred to vanadium enriched media. Key words: vanadium, germination, seedling growth, Lactuca sativa.
Introduction Vanadium is a relatively uncommon constituent of the earth's crust, its frequency being of the same order of magnitude as Cu, Ni, Pb or Zn (BERTRAND, 1960). This author details sources of vanadium in the geosphere; these include petrochemicals, petrochemical-bearing schists and fossil fuels. Vanadium release into the environment comes when fossil fuels and petrochemicals are combusted (ZOLLER, 1971). A recent report (JACKS, 1976) describes the accumulation of vanadium in a semiurban locality in Sweden, and BROSSETT (1976) reports air pollution episodes in the same country where vanadium-rich particulates predominate. In view of the apparent increase of vanadium in the biosphere, the effects of this element on living organisms should be considered. In regard to plants, studies relating to vanadium are sparse and scattered. Vanadium is toxic to plants, when levels of «available» vanadium in soils exceed 20 ppm (CANNON, 1963; NASON and McELROY, 1963). Beneficial responses to lower levels of vanadium have also been reported. ARNON and WESSEL (1953) claim this element is essential for green algae, whilst a beneficial response of mature sugar beets to vanadium is reported by SINGH and WORT (1969). Studies on seed germination are somewhat contradictory. CANNON (1963) found no response of Sorghum, with regard to seed germination and subsequent seedling growth, to 1 ppm vanadium. CATALINA (1966) found stimulation of germination of a range of species in response to vanadium applications of between 1 and 50 ppm. Z. Pjlanzenphysiol. Ed. 83, S. 185-188.1977.
186
N. W.
LEPp
This study also revealed a concomitant increase in activity of various enzymes following vanadium treatment of seeds. The present study was undertaken to provide a clearer insight into the effects of vanadium on seed germination and subsequent seedling growth of Lettuce, with a view to establishing the true status of this element with regard to phytotoxicity. Materials and Methods Seeds of Lactuca sativa L. C. V. SALAD BOWl, obtained from a commercial sou used in all experiments. Batches of 50 seeds were sown on filter paper circles contained in petri dishes, then irrigated with 2 ml of the appropriate solution. Treated seeds were placed in constant illumination at 20°C. Under these conditions, germination occurred within 48 hours. Seedlings were harvested, weighed and measured after 7 days growth. In the transfer experiments, seedlings were germinated in the absence of vanadium, then transferred to appropriate vanadium treatments after 3 days. Such seedlings were harvested after a further 4 days growth. In all experiments, vanadium was supplied as VOS0 4 solution at concentrations between 50 and 0.05 ppm.
Results and Discussion Table 1 illustrates the effect of a range of vanadium concentrations on seed germination and subsequent seedling growth. Several points emerge from these results. First, none of the vanadium treatments significantly altered germination percentage. However, subsequent seedling growth is markedly affected by increasing concentration of vanadium. Fresh weight increases are significantly reduced, and there is a concomitant reduction of root and shoot extension, 86 % reduction of both root and shoot extension is recorded at the highest vanadium concentration (50 ppm). Such quantitative changes were also accompanied by some striking alterations in the morphology of the seedlings. At vanadium concentrations of 5 and 50 ppm,
Table 1: Effect of vanadium on various properties of germinating lettuce seedlings. Germ.
Fresh wt.
50 5 0.5 .05
52 52 51 47
0.23 0.57 0.61 0.66
Control
56
ppmV
%
± ± ± ± 0.92 ±
.03 .09 .04 .08 .12
Root Length
± ± ± ± 37.56 ±
5.14 16.94 23.65 24.91
.95 2.54 3.05 2.08 2.55
(86) (55) (37) (33)
Shoot Length
± ± ± ± 17.2 ±
2.27 5.07 8.31 12.3
0.25 1.23 1.83 1.64
(86) (70) (52) (28)
1.64
germination scored at 72 hours. Remaining measurements made 7 days after sowing. Means ± S. E's (at p ~ 0.05) are given for all germinated seedlings. Fresh weights are given for 10 randomly selected seedlings from each treatment. Figures in brackets refer to % growth reduction (against the control). Fresh weights are given in gms, root and shoot length" in mm.
0/0
z.
Pjlanzenphysiol. Bd. 83, S. 185-188.1977.
Effect of Vanadium on germination
187
marked helicoid orientation of seedlings was obst::rved, showing similarities to those reported by PUERNER and SIEGEL (1972) for cucumber seedlings exposed to high levels of several heavy metals. Roots produced by these plants were branched, and at 50 ppm vanadium, progressive root die-back was noted. This was manifest as the occurrence of necrotic apices, together with the production of numerous peg-like secondary roots. CANNON (1963) reports that morphological symptoms of vanadium toxicity include reddening of young leaves, followed by chlorosis. Seedlings grown in 50 ppm vanadium exhibited a degree of reddening, but no apparent chlorosis. Table 2: Effect of vanadium treatment subsequent to germination on various properties of lettuce seedlings. ppmV 50 5 0.5 0.05 Control Seedlings grown in vanadium solution. Means ± S. E's (at reductions (against given III mm.
Fresh wt.
± ± ± ± 0.178 ±
0.102 0.134 0.154 0.158
.014 .008 .013 .001 .009
Root Length
± ± ± ± 52.9 ± 25.2 34.1 43.9 49.9
5.1 (52) 3.4 (45) 5.6 (27) 5.0 (6) 3.7
Shoot Length
± ± ± ± 22.5 ± 13.7 16.3 19.3 2004
1.04 1.06 1.13 1.19
(46) (32) (16) (8)
.083
distilled water for 72 hours, then 10 uniform seedlings transferred to Measurements made after 4 further days in the respective treatments. p ~ 0.05) given for all seedlings. Figures in brackets refer to Ofo growth the control). Fresh weights are given in gms, root and shoot lengths
Table 2 illustrates the response of seedlings to vanadium application following a period of normal growth. From these results, it can be seen that vanadium still inhibits growth, but to a somewhat lesser extent. The reddening effect at 50 ppm vanadium was again evident, but no other morphological abnormalities were evident. These results provide some evidence as to the phytotoxic potential of vanadium. It is quite clear that levels in excess of 5 ppm applied vanadium can markedly reduce growth of lettuce seedlings and in some cases produce quite distinct morphological changes. It is evident that vanadium can be absorbed by roots [as found by WELCH (1973)], accumulated within these tissues, and may also be transported to the shoot. The mechanism of toxicity is not clear, but two possibilities could exist. Firstly vanadium could be enhancing the activity of various enzymes, particularly those involved in regulating hormone levels. It has been established that copper can affect IAA-oxidase activity (MUKHERJI and DAS GUPTA, 1972; COOMBES et al., 1976); vanadium may have a similar effect. Alternatively vanadium could affect the available calcium status of the seedlings. CANNON (1963) presents evidence for interaction between calcium and vanadium in plant tissues. Vanadium will readily combine with calcium to form insoluble calcium vanadate, deposits of this being observed in roots of naturally calcium-rich plants grown in vanadiumcontaining
z.
Pflanzenphysiol. Bd. 83, S. 185-188. 1977.
188
N. W. LEPP
media. It is possible that growth of seedlings at the higher vanadum treatments is being arrested due to an increase in calcium vanadate formation, with a resultant decrease in calcium available for cell-wall formation. Further work is work is clearly required to resolve the mechanism of vanadium toxicity. The present results serve to highlight the phytotoxic potential of this element, but a re-appraisal of its present status as an environmental contaminant clearly requires a more exhaustive examination. References ARNON, D. ]., and G. WESSEL: Vanadium as an essential element for green plants. Nature. 172, 1040 (1953). BERTRAND, D.: The biogeochemistry of vanadium. In Survey of contemporary knowledge of biogeochemistry. Am. Mus. Nat. History. Bul!. 94, 409-455 (1950). BROSSET, c.: Airborne particles: Black and white episodes. Ambio. 5,157-163. (1976). CANNON, H.: The biogeochemistry of vanadium. Soil Sci. 96, 196-204 (1963). CATALINA, L.: Influence of vanadium on germination. An. Edafo!' Agrobio!. (Madrid). 25, 551-559 (1966). COOMBES, A. ]., N. W. LEPP, and D. A. PHIPPS: The effect of copper on IAA-oxidase activity in root tissue of Barley (Hordeum vulgare L. C. V. ZEZHYR). Z. Pflanzenphysio!. 80,236-242 (1976). JACKS, G.: Vanadium in an area just outside Stockholm. Environ. Pollut. 11, 289-295 (1976). MUKHERJI, S., and B. DAS GUPTA: Characterisation of copper toxicity in lettuce seedlings. Physio!. Plant. 27, 126-129 (1972). NASON, A., and W. D. McELROY: Modes of action of essential mineral elements. In Plant Physiology: A treatise. edit. STEWARD, F. C. 3, 451-536. Academic Press, New York, 1963. PUERNER, N. ]., and S. M. SIEGEL: The effects of mercury compounds on the growth and orientation of cucumber seedlings. Physio!. Plant. 26, 310-312 (1972). SINGH, B. B., and D. ]. WORT: Effect of vanadium on growth, chemical composltlon and and metabolic processes of mature sugar beet (Beta vulgaris L.) plants. P!. Physio!. 44, 1321-1327 (1969). WELCH, R. M.: Vanadium uptake by plants. Absorption kinetics and the effect of pH, metabolic inhibitors and other anions and cations. P!. Physio!. 51, 828-832 (1973). ZOLLER, W. H.: The distribution of vanadium in the atmosphere. Nat. Mag. Am. Chern. Soc. 162,12-17 (1971).
Dr. N. W. LEPP, Department of Biology, Liverpool Polytechnic, Byrom Street, Liverpool L3 3AF, U.K.
Z. P/lanzenphysiol. Bd. 83, S. 185-188.1977.