Environmental Engineering Reference
In-Depth Information
Ahmad et al. 2007 ). Such selective nutrient deiciency may retard metabolic processes
and ultimately produce Ni toxicity in plants (Genrich et al. 1998 ; Gajewska et al.
2006 ; Gonçalves et al. 2007 ). Nickel may also suppress growth and development
and reduce agricultural crop yields (Nedhi et al. 1990 ; Rao and Sresty 2000 ;
Boominathan and Doran 2002 ; Seregin and Kozhevnikova 2006 ). In addition, some
metals (e.g., Fe, Cu, Zn, and Mn) are integral to certain metalloenzymes such as
superoxide dismutase (SOD) and catalase (CAT). Therefore, if Ni competes with or
otherwise affects their presence, then reduced biosynthesis may result (Molas 2002 ;
Gajewska et al. 2006 ).
10
Yield and Yield Components
High Ni levels are known to reduce crop yields. Reduced yields in the presence of
Ni has been documented to have occurred in: mungbean (Ahmad et al. 2007 ), tomato
(Balaguer et al. 1998 ), cucumber (Aziz et al. 2007 ; Tabatabaei 2009 ), and sunlower
(Lavado 2006 ). Nickel-induced crop yield decreases usually result from impaired
root absorption of nutrients (Kochian 1991 ; Hasinur et al. 2005 ), impaired plant
metabolism (Pandey and Sharma 2002 ), and/or a decline in photosynthesis and tran-
spiration rates (Sheoran et al. 1990 ; Shi and Cai 2008 ). Matraszek et al. ( 2002 ) stud-
ied the effect of different Ni levels on the yield of vegetables (i.e., spinach, lettuce,
and Phaseolus vulgaris) . Their results showed that the yield of usable plant parts
was signiicantly reduced, even at very low Ni concentrations (10 mg L −1 ). Similarly,
Singh and Nayyar ( 2001 ) reported that dry matter production in cowpea was reduced
at soil concentrations of 50 mg Ni kg −1 and above. They further showed that cowpea
tolerates relatively higher amounts of Ni in the soil, than does other crops. By con-
trast, lower Ni levels (i.e., 50 mg kg −1 soil) strongly improved yields of some plant
species (Atta-Aly 1999 ).
Nickel negatively affects the length and fresh weight of stems, branches and the
leaf fresh weight of many plants. It also reduces lowers and fruits of several plant
species (Balaguer et al. 1998 ; Mizuno et al. 2003 ). An example of Ni toxicity
appeared in four cultivars of blackgram ( Vigna mungo ), grown in sandy loam soil
(pH 6.3) and amended with 0, 50, 100, 150, or 200 mg Ni kg −1 ; these plants dis-
played a reduction in the following: root and shoot lengths, dry matter yields, num-
ber of root nodules, and leaf area (Chawan 1995 ).
Root length, plant weight, leaf area, and seed yield in wheat ( Triticum aestivum )
were signiicantly affected by Ni exposures from 0 to 1,000 mg L −1 . A maximum
spike length was observed at 100 mg Ni L −1 ; however, at 25 mg L −1 of Ni, seed weight
per 100 seeds was at the maximum (Yadav and Aery 2002 ; Keeling et al. 2003 ).
Ultimately, crop yield depends on the interplay among a multitude metabolic pro-
cesses that occur at various plant life cycle stages. These processes result in a yield
of seed or biomass, or both, and the foregoing results indicate that the presence of
Ni may affect such yield.
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