Growth stimulation effects of smoke-water and vermicompost leachate on greenhouse grown-tissue-cultured ‘Williams’ bananas

A common problem often experienced by both small and large scale banana farmers is the reduction in quality and yield of bananas due to soil moisture deficits and declining soil fertility. To overcome this, mechanisms of improving yield without compromising environmental integrity or public health are being embraced. Globally, researchers have continued to evaluate the competence of environmental-friendly organic fertilizers and smoke solutions to improve the growth, yield and quality of various crops. In the present study, the effect of smoke-water (1:1,000; 1:500 and 1:250 dilutions) and vermicompost leachate (1:20; 1:10 and 1:5 dilutions) treatments on the growth of greenhouse grown bananas was evaluated. Soil drenching (smoke-water and vermicompost leachate) and foliar application (smoke-water) were tested on 1-month-old tissue-cultured banana seedlings under greenhouse conditions. After 3 months, growth parameters such as number and length of roots and shoots; number of leaves and leaf area as well as their fresh and dry weights were analyzed. Soil drenching with smoke-water significantly increased the root length (1:1,000 and 1:500 dilutions) as well as fresh and dry weight (1:1,000; 1:500 and 1:250 dilutions) when compared to foliar application. Vermicompost leachate (1:10 and 1:5 dilutions) significantly enhanced the shoot length, root length, leaf area and dry weights. Vermicompost leachate (1:20; 1:10 and 1:5 dilutions) also significantly increased the number of off-shoots. The positive effect on rooting is beneficial for acclimatization and establishment of tissue-cultured banana plantlets in nurseries and subsequent transfer to the field. Moreover, the high cost of inorganic fertilizers as well as environmental safety concerns makes the use of smoke-water and vermicompost leachate potential alternatives to improving the growth and cultivation of bananas.     

Competitive effects of the invasive shrub,Lonicera maackii (Rupr.) Herder (Caprifoliaceae), on the growth and survival of native tree seedlings

Invasive plants are often associated with reduced cover of native plants, but rarely has competition between invasives and natives been assessed experimentally. The shrub Lonicera maackii, native to northeastern Asia, has invaded forests and old fields in numerous parts of eastern North America, and is associated with reduced tree seedling density in Ohio forests. A field experiment was conducted to test the effects of established L. maackii on the survival and growth of transplanted native tree species. The experiment examined above-ground competition (by removing L. maackii shoots) and below-ground competition (by trenching around transplanted seedlings). The effects of above-ground competition with L. maackii were generally more important than below-ground competition, though both were detected. Shoot treatment was the key determinant for the survival of all species except P. serotina, whereas trenching only enhanced survival for A. saccharum caged and P. serotina, and only in the shoot removal treatment. For the surviving seedlings, L. maackii shoot removal increased growth of A. saccharum seedlings protected with cages, but actually reduced the growth of unprotected Q. rubra and A. saccharum seedlings, indicating that L. maackii shoots confer some protection from deer browsing. Significant interactions between root and shoot treatment on Q. rubra growth parameters, specifically greatest growth in the shoot present & trenched treatment, is attributed to protection from deer browsing combined with release from below-ground competition. Despite this protective function of L. maackii shoots, the overall effect of this invasive shrub is increased mortality of native tree seedlings, suggesting it impacts the natural regeneration of secondary forests.     

Carbon dioxide-gassed fluorocarbon enhances micropropagation of rose (Rosa chinesis Jacq.)

The inert perfluorochemical (PFC) liquid, perfluorodecalin (Flutec PP6), has been used to increase the CO₂ supply to cultured shoots of Rosa chinensis Jacq. cv. Baby Love. Culture of shoots in semi-solid medium overlaying CO₂-gassed PFC (2 mbar; 5 min repeated every 7 days) for up to 42 days, increased biomass as reflected by significant (P<0.01) increases in shoot number, number of leaves per shoot and mean shoot fresh weight. Additionally, there were significant (P<0.01) increases in the number of roots and their fresh and dry weights following a further 10 days of culture on rooting medium prior to transfer of plants to the glasshouse. Treatment of cultured rose shoots with CO₂-gassed PFC also significantly reduced (P<0.01) the accumulation of phenolic compounds in roots. The total chlorophyll of aerial parts was unaffected, although total protein in shoots and roots was significantly (P<0.01) lower than in the control. The biotechnological implications of this novel cultural régime are discussed for the micropropagation of woody species. Received: 5 June 1996 / Revision received: 29 July 1996 / Accepted 19 August 1996     

Testing a new hypothesis: plant vigor and phylloxera distribution on wild grape in Arizona

Summary Longer, meaning more vigorous, shoots of a wild grape clone (Vitis arizonica) were more susceptible to attack by second and third generations of leaf-galling grape phylloxera,Daktulopsphaira vitifoliae, as the growing season progressed. Although there was no significant difference in mean shoot length between attacked and unattacked shoots within a clone at the beginning of shoot elongation, attacked shoots were significantly longer than unattacked shoots when elongation had ceased (P<0.01). Also, long attacked shoots had a significantly greater population of phylloxera galls than short attacked shoots (P<0.01) as the season progressed. The phylloxera population on long shoots increased rapidly while the population on short shoots remained the same. Longer shoots also produced significantly more axillary shoots than shorter shoots as the season progressed (P<0.001), and the number of axillary shoots accounted for 66 percent of the variance in number of attacked leaves on a shoot. Experimental evidence showed that there was a significantly greater percentage of available leaves attacked on long shoots than on short shoots (P<0.05) and the leaves on long shoots generally had a greater number of galls per leaf. The relationship between shoot length and probability of attack was also tested by comparing shoots lengths of 10 attacked clones and 10 unattacked clones at a second location. Mean shoot lengths of attacked clones were significantly longer than mean shoot lengths of unattacked clones (P<0.05), and mean shoot lengths of attacked shoots within a clone were significantly longer than unattacked shoots (P<0.001). Longer shoot length accounted for 81 percent of the variance in probability of attack. The reason for this pattern of attack was that long shoots produced newly expanding leaves over a longer time during the growing season and multivoltine phylloxera require undifferentiated tissue to initiate gall formation. Patterns of attack within a shoot were characterized by an uneven distribution of galls among leaves. This was due to development time between generations and the current availability of undifferentiated tissue at times of colonization. This study supports the hypothesis that some herbivore species are favored more by vigorous plants than by stressed plants.     

Cytokinins,donor plants and time in culture affect shoot regenerative capacity of American elm leaves

Cytokinins, donor plants and their time in vitro as well as basal media were investigated for their influence on shoot regenerative capacity of American elm (Ulmus americana L.) leaves. Leaves excised from six 2-year-old seedlings formed adventitious shoots when placed on Driver and Kuniyuki Walnut (DKW) medium supplemented with 7.5, 15 or 22.5 M of benzyladenine (BA) or thidiazuron (TDZ). Thidiazuron induced significantly higher regeneration percentages on elm leaves than BA, regardless of concentration used. Donor plant also affected the efficiency of shoot regeneration, with certain seedlings having 1.5 to 7 times more explants forming shoots as compared to other seedlings tested. By subculture 15, the average number of shoots per regenerating explant increased at least 3-fold for leaves on media with BA or TDZ for the one donor plant that survived continued subculturing. Leaf explants from donor plants with the highest regenerative capacity had a higher percentage of shoot formation on DKW than MS medium. Explants from productive donor plants should be placed on DKW medium supplemented with TDZ to improve shoot regeneration efficiency from American elm leaves.     

In vitro differentiation of multiple shoot clumps from intact seedlings of switchgrass

Summary An efficient and reproduciblein vitro culture system has been developed for regeneration of multiple shoot clumps from intact seedlings of both lowland and upland cultivars of switchgrass (Panicum virgatum L.). The multiple shoots were induced on Murashige and Skoog medium supplemented with various combinations of 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-phenyl-3-(1,2,3-thiadiazol-5YL)-urea (thidiazuron or TDZ). Maximum response was obtained with 4.5 μM 2,4-D and 18.2 μM TDZ. These shoots proliferated and rooted efficiently on MS medium without growth regulators. The developmental pattern of the multiple shoots indicated their origin from the enlarged shoot apex via proliferation of axillary buds and subsequent reprogramming of shoot meristems followed by secondary differentiation of adventitious shoots The simplicity of the protocol and direct production of multiple shoots make this a potential system that is highly attractive and amenable for microprojectile-mediated gene transfer.     

Iron accumulation on the cell wall of the aquatic moss Drepanocladus fluitans in an acid lake at pH 3.4–3.8

Iron accumulation was studied in shoots of the aquatic moss Drepanocladus fluitans (Hedw.) Warnst collected from an acid lake and stream. The concentration of iron in the shoots of the moss from Lake Usoriko (pH 3.4–3.8) increased from the tip toward the base and ranged from 0.07 to 10% on a dry weight basis. The iron concentration in the lake water was 0.15 mg 1^–1. In contrast, iron concentration in the shoots of D. fluitans from Kashiranashigawa stream (pH 4.2–4.7), one of the streams flowing into Lake Usoriko, was only 0.02 mg g^–1 at the shoot tip and 0.3% at the shoot base, while that in the stream water was <0.02 mg 1^–1. Transmission electron microscopy using a X-ray microanalyzer (TEM-XMA) study revealed accumulation of needle-like iron crystals on the cell wall and decomposed cell components. In addition, many rod-type bacteria were found in the accumulated iron deposits.The accumulation of iron in the shoots of D. fluitans is due to two processes: biological accumulation of essential iron dissolved in acid water, and abiological crystal growth on the surface of organic particulate material including the cell wall.     

Differential biochemical responses of wheat shoots and roots to nickel stress: antioxidative reactions and proline accumulation

Wheat (Triticum aestivum L. cv. ‘Zyta’) seedlings were treated with 10, 100 and 200 μM Ni. Tissue Ni accumulation, length, relative water content (RWC), proline and H₂O₂ concentrations as well as the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (POD) and glutathione S-transferase (GST) were studied in the shoots and roots after 6 days of Ni exposure. Treatment with Ni, except for its lowest concentration, resulted in a significant reduction in wheat growth. In comparison to the shoots, the roots showed greater inhibition of elongation, which corresponded with higher accumulation of Ni in these organs. Both shoots and roots responded to Ni application with a decrease in RWC and enhancement in proline concentration. Greater dehydration of the shoot tissue was accompanied by more intense accumulation of proline. Treatment of the wheat seedlings with the highest concentration of Ni led to about 60% increase in H₂O₂ concentration in both studied organs. Apart from CAT, constitutive activities of antioxidative enzymes were much higher in the roots than in the shoots. Exposure of the seedlings to Ni resulted in SOD activity decline, which was more marked in the roots. While the shoots showed a substantial decrease (up to 30%) in CAT activity, in the roots the activity of this enzyme remained unchanged. After Ni application APX, POD and GST activities increased several-fold in the shoots, whereas in the roots they were not significantly altered. The results suggest that differential antioxidative responses of the shoots and roots of wheat seedlings to Ni stress might be related to diverse constitutive levels of antioxidant enzyme activities in both organs.     

Overexpression of Arabidopsis phytochelatin synthase in tobacco plants enhances Cd2+ tolerance and accumulation but not translocation to the shoot

Phytochelatins (PCs) are metal binding peptides involved in heavy metal detoxification. To assess whether enhanced phytochelatin synthesis would increase heavy metal tolerance and accumulation in plants, we overexpressed the Arabidopsis phytochelatin synthase gene (AtPCS1) in the non-accumulator plant Nicotiana tabacum. Wild-type plants and plants harbouring the Agrobacterium rhizogenes rolB oncogene were transformed with a 35S AtPCS1 construct. Root cultures from rolB plants could be easily established and we demonstrated here that they represent a reliable system to study heavy metal tolerance. Cd²⁺ tolerance in cultured rolB roots was increased as a result of overexpression of AtPCS1, and further enhanced when reduced glutathione (GSH, the substrate of PCS1) was added to the culture medium. Accordingly, HPLC analysis showed that total PC production in PCS1-overexpressing rolB roots was higher than in rolB roots in the presence of GSH. Overexpression of AtPCS1 in whole seedlings led to a twofold increase in Cd²⁺ accumulation in the roots and shoots of both rolB and wild-type seedlings. Similarly, a significant increase in Cd²⁺ accumulation linked to a higher production of PCs in both roots and shoots was observed in adult plants. However, the percentage of Cd²⁺ translocated to the shoots of seedlings and adult overexpressing plants was unaffected. We conclude that the increase in Cd²⁺ tolerance and accumulation of PCS1 overexpressing plants is directly related to the availability of GSH, while overexpression of phytochelatin synthase does not enhance long distance root-to-shoot Cd²⁺ transport.     

Structure and Dynamics of Populations of Japanese Barberry (Berberis Thunbergii DC.) in Deciduous Forests of New Jersey

Japanese barberry, Berberis thunbergii DC., has become a prominent exotic species in deciduous forests throughout the eastern and midwestern US. Populations range from small plants occurring at low densities to dense, impenetrable thickets of plants with up to 40 stems/individual. A study was undertaken at Morristown National Historical Park in New Jersey to document plant densities, plant size, recruitment through vegetative processes of new shoot initiation and clonal spread and recruitment from seedling establishment, and mortality of stems and plants. Nearly 2000 shoots on 370 plants were individually marked and followed for two growing seasons, and over 1000 seedlings were also individually marked and followed. Populations vary much more in total shoots/area than they do in plant individuals/area, or in mean plant size (shoots/plant), as even the sparse populations have a few large individuals. Shoot mortality is less than new shoot initiation, but most plants do not change in size or change by small numbers of stems. However, the number of new shoots per plant increases as plant size increases. Once plants have three stems, they suffer little or no mortality. Seedling establishment is proportional to the density of shoots, so that as plants grow in size, local recruitment from seed increases. Large numbers of seedlings, and a survival rate of 10%, combine to make seedling recruitment a major component of population increase. The combination of multiple forms of vegetative and seed-based population growth, and the very low rates of plant mortality due to the multi-stemmed growth form explains the ability of this invasive species to rapidly produce dense, persistent populations.     

Thidiazuron induced high frequency axillary shoot multiplication in Psoralea corylifolia

The effect of thidiazuron (TDZ) was studied on in vitro axillary shoot proliferation from nodal explant of Psoralea corylifolia - an endangered medicinal plant. Proliferation of shoots was achieved on Murashige and Skoog (MS) medium supplemented with 0.5, 1, 2, 3, 4 and 5 μM TDZ. The maximum number (13.6 ± 1.4) of shoots per explant were obtained from nodal segment cultured on 2 μM TDZ for 4 weeks and this increased to 29.7 ± 2.1 on hormone free MS medium after 8 weeks. The in vitro proliferated and elongated shoots were transferred individually on a root induction medium containing 0.5 μM indole-3-butyric acid (IBA) and within 4 weeks 4.5 ± 0.5 roots per shoot were produced. The regenerated plantlets were transferred to 1:1 soil and vermiculite mixture and acclimatized with 80 % survival rate. Fully acclimatized plants were grown in garden soil in greenhouse and their morphological and physiological parameters were comparable with seedlings.     

Effect of silicate on the growth and arsenate uptake by rice (Oryza sativa L.) seedlings in solution culture

A solution culture experiment was conducted to investigate the effect of silicate on the yield and arsenate uptake by rice. Rice seedlings (Oryza sativaL. cv. Weiyou 77) were cultured in modified Hoagland nutrient solution containing three arsenate levels (0, 0.5 and 1.0 mg L ^–1 As) and four silicate levels (0, 14, 28 and 56 mg L ^–1 Si). Addition of Si significantly increased shoot dry weight (P=0.001) but had little effect on root dry weight (P=0.43). Addition of As had no significant effect on shoot dry weight (P=0.43) but significantly increased root dry weight (P=0.01). Silicon concentrations in shoots and roots increased proportionally to increasing amounts of externally supplied Si (P < 0.001). The presence of As in the nutrient solution had little effect on shoot Si concentration (P=0.16) but significantly decreased root Si concentration (P=0.005). Increasing external Si concentration significantly decreased shoot and root As concentrations and total As uptake by rice seedlings (P <0.001). In addition, Si significantly decreased shoot P concentration and shoot P uptake (P <0.001). The data clearly demonstrate a beneficial effect of Si on the growth of rice seedlings. Addition of Si to the growth medium also inhibited the uptake of arsenate and phosphate by the rice seedlings.     

Multiple shoot induction by benzyladenine and complete plant regeneration from seed explants of chickpea (Cicer arietinum L.)

The efficacy of benzyladenine (BA) to induce multiple shoots from seed explants of chickpea (Cicer arietinum L.) was assessed. Shoot differentiation was influenced by the type of seed explant, genotype and concentration of BA. Orientation of the explant also strongly influenced the shoot regeneration response. The optimum BA concentration for shoot/shoot bud regeneration was genotype dependent. Two types of BA-induced response were observed: (1) at less than 7.5 gm BA, direct shoot differentiation (2 to 4-cm-long shoots) was observed within 30 days; (2) at higher BA concentrations (75–100 m), shoot/shoot bud differentiation was achieved in 45–90 days. A high BA concentration inhibited subsequent rooting of shoots. Roots, however, could be easily induced on shoots derived from <12.5 m BA. Following transfer to soil, 80% of the regenerants developed into morphologically normal and fertile plants.Abbreviations BA Benzyladenine     

Gas Exchange,Leaf Structure,and Hydraulic Features in Relation to Sex,Shoot Form,and Leaf Form in An Evergreen Shrub Sabina vulgaris in the Semi-Arid Mu Us Sandland in China

We examined differences in net photosynthetic rate (P _N), transpiration rate (E), water use efficiency (WUE), ratio of substomatal to atmospheric CO₂ concentration (C _i/C _a), cuticle thickness (CT), epidermis cell size (ECS), mesophyll cell size (MCS), vascular bundle size (VBS), tissue density (TD), and coefficient of water loss (k) in Sabina vulgaris as related to sex, shoot form, and leaf form. P _N, E, WUE, C _i/C _a, MCS, VBS, and k varied with sex, whereas CT, ECS, and TD did not. These differences in physiology and anatomy between the female and male plants may be closely related with their reproduction behaviour. P _N, E, C _i/C _a, CT, ECS, MCS, and VBS were significantly smaller in the erect shoots than in the prostrate shoots, WUE was just opposite; TD and k did not vary with shoot form. These changes in physiology with shoot form indicate that erect shoots may be more tolerant of water stress than prostrate shoots. P _N, E, C _i/C _a, TD, and k were significantly greater in the spine leaves than in the scale leaves, whereas WUE, CT, ECS, MCS, and VBS followed the opposite trends. The changes in physiology and anatomy with leaf form suggest that scale leaves have higher drought-resistant and water-holding capacities than spine leaves. Measurements of field gas exchange showed that three-year-old seedlings had lower drought-resistance and higher water loss than five-year-old seedlings, which provides some evidence that seedling survival decreases with decreasing plant age.     

A protocol for rapid micropropagation of endangered Isoplexis

Summary An efficient protocol for large-scale micropropagation of Isoplexis canariensis (L.) Loud., I. chalcantha Svent, and O'Shan., and I. isabelliana (Webb and Berth.) Masf. (Scrophulariaceae) is reported. Multiple shoots were obtained from shoot tips and nodal segments isolated from seedlings when cultured under varying conditions. Factors such as nutrient media, concentration of growth regulators, and type of induction medium (liquid or solid) strongly influenced shoot proliferation and development. Multiple well-developed shoots were obtained after induction on solid media containing Murashige and Skoog full-strength salts and low cytokinin concentrations. By changing the major salt formulation to half strength and employing liquid media the morphogenic parameters evaluated were affected negatively. Many shoots rooted spontaneously in hormone-free media and plants grew successfully in the greenhouse. Flowering was observed 6 mo. after ex vitro cultures were established.     

An efficient protocol for the regeneration of whole plants of chickpea (Cicer arietinum L.) by using axillary meristem explants derived from in vitro-germinated seedlings

Summary An efficient and reproducible protocol for the regeneration of shoots at high frequency was developed by using explants derived from the axillary meristems from the cotyledonary nodes of in vitro-germinated seedlings of chickpea (Cicer arietinum L.). Culture conditions for various stages of adventitious shoot regeneration including the induction, elongation, and rooting of the elongated shoots were optimized. The medium for synchronous induction of multiple shoot buds consisted of Murashige and Skoog basal medium (MS) with low concentrations of thidiazuron (TDZ), 2-isopentenyladenine (2-iP), and kinetin. Exclusion of TDZ and lowering the concentration of 2-iP and kinetin in the elongation medium resulted in faster and enhanced frequency of elongated shoots. Cultivation of the stunted shoots on MS with giberellic acid (GA₃) increased the number of elongated shoots from the responding explants. pH of the medium played a very crucial role in the regeneration of multiple shoot buds from the explants derived from cotyledonary nodes. A novel rooting system was developed by placing the elongated shoot on a filter paper bridge immersed in liquid rooting medium that resulted in rooting frequency of up to 90%. A comprehensive protocol for successful transplantation of the in vitro-produced plants is reported. This method will be very useful for the genetic manipulation of chickpea for its agronomic improvement.     

In vitro regeneration of plantlets in Brassica alboglabra

Different vegetative parts of Brassica alboglabra seedlings and mature plants were used as explants in culture.A high frequency (60–100%) of shoot regeneration was obtained from hypocotyl explants, nodal stem segments, internodal segments and shoot apices cultured on Murashige-Skoog basal medium. Addition of 6-benzylaminopurine and kinetin increased the average number of shoots per explant. When detached and transferred to basal medium, the shoots readily developed roots. Regenerated plantlets could be successfully transplanted in soil.     

In vitro regeneration of Ruscus hypophyllum L. plants

Callus cultures were established from stem explants of Ruscus hypophyllum on a modified basal medium of Murashige and Skoog (1962) supplemented with 1 mg l^-1 2,4-D+0.1 mg l^-1 BAP. The optimal 2,4-D concentration for promoting shoot bud formation and growth was 0.05 mg l^-1 along with 0.5 mg l^-1 BAP. Sixty percent of rootless shoots produced flowers on the regenerating medium. Rooting was induced when shoots were transferred to half strength MS inorganic salts supplemented with 2 mg l^-1 IBA. Eighty percent of plants transferred to soil have survived.     

In vitro multiplication and plantlet establishment of avocado

Summary A procedure is described to regenerate shoots and plants from the embryonic axis of avocado seedlings with benzyladenine or thidiazuron. Explants were grown in the dark for 10 d and then transferred to an 18-h photoperiod to induce multiple shoots. Increased concentrations of benzyladenine or thidiazuron resulted in increased shoot production. Shoots were transferred to shoot promoting media where additional shoots were formed. Under the best conditions, six rooted shoots were produced per original explant. About 80% of the shoots with roots survived in the glasshouse and produced normal phenotypic plants.     

Tissue partitioning of cadmium in transgenic tobacco seedlings and field grown plants expressing the mouse metallothionein I gene

Since agricultural crops contribute >70% of human cadmium (Cd) intake, modification of crops to reduce accumulation of this pollutant metal during plant growth is desirable. Here we describe Cd accumulation characteristics of seedlings and field grown tobacco plants expressing the Cd-chelating protein, mouse metallothionein I. The objective of the transformation is to entrap Cd in roots as Cd-metallothionein and thereby reduce its accumulation in the shoot. Transformed and control seedlings were exposed for 15 days in liquid culture at a field soil-solution-like Cd concentration of 0.02 μm. Transformed seedlings ofNicotiana tabacum cultivar KY 14 contained about 24% lower Cd concentration in shoots and about 5% higher Cd concentration in roots than control seedlings. Dry weights of transformed and control tissues did not differ significantly. In the field in 1990, mature transformedN. tabacum cv. KY 14 plants exposed only to endogenous soil Cd contained about 14% lower leaf lamina Cd concentration than did controls. Differences were significant at thep≤0.1 level in 13 of 16 leaf positions. Leaf dry weight did not differ significantly but transformed field plants had 12% fewer leaves and were 9% shorter than the controls. Copper (Cu) concentration was significantly higher (ca10%) in the bottom nine leaf positions of transformed plants suggesting that reduced leaf number and plant height may be due to Cu deficiency or toxicity. Alternatively, somaclonal variation or gene position effects may be involved. No differences were found in zinc levels. WithN. tabacum cv. Petit Havana, transformed seedlings contained no less Cd in shoots but 48% higher Cd concentration in roots. However, dry weights of shoots and roots of transformed seedlings were 25% and 26%, respectively, greater than in controls. In the field, transformed and control plants of this cultivar showed little significant differences in leaf Cd content, plant height or leaf number. Although comparison of additional metallothionein-expressing tobaccos and other plants is needed, results obtained with cultivar KY 14 support the hypothesis that sequestration of Cd in roots as Cd-metallothionein may have potential for reducing Cd content of above root tissues of certain plants.