Effect of the Heavy Metals on Developmental Stages of Ovule, Pollen, and Root Proteins in Reseda lutea L. (Resedaceae)

Laboratory of Plant Cell Developmental Biology, Department of Biology, Bu-Ali Sina University, Hamedan, Iran.
Biological trace element research (Impact Factor: 1.75). 03/2011; 143(3):1777-88. DOI: 10.1007/s12011-011-9009-x
Source: PubMed


Heavy metals are some of the most important environmental pollutants. Excessive amounts of heavy metals adversely affect plant growth and development. Also, the presence of elevated levels of heavy metal ions triggers a wide range of cellular responses including changes in gene expression and synthesis of metal-detoxifying peptides. The overall objective of this research was to elucidate some microscopic effects of heavy metals on the formation, development, and structure of pollen, ovule, and embryo and also root proteins in Reseda lutea L. For this purpose, the vicinity of Ahangaran lead-zinc mine (Hamedan, Iran) was chosen as a polluted area where amount of some heavy metals was several times higher than the natural soils. Flowers and young buds were collected from non-polluted and polluted plants, fixed in FAA(70), and studied during developmental stages by light microscopy. The results showed that heavy metals can cause some abnormalities during the pollen and ovule developmental process. The number of pollen grains was decreased, and their shape was changed. Increasing in thickness of the callosic wall and stabilizing of tapetum layer were observed in polluted plants. Asymmetrical formation of ovular integuments, degradation of egg apparatus, irregular formation of embryo sac, considerable vacuolation of embryonic cells, and degeneration of embryo in the late stage of heart-shaped embryo are the results of heavy metal pollution. For protein studies, young roots were harvested from plants exposed to pollution and non-exposed to pollution at the same time. Root proteins were extracted and studied by electrophoresis. The results revealed that some new proteins were synthesized in polluted samples that probably elevate plant tolerance to heavy metals.

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    • "Metal hyperaccumulators sequester heavy metals in their tissues at levels oft en toxic to herbivores and other plants ( Brooks et al., 1977 ; Boyd et al., 1994 ; Martens and Boyd, 1994 ; Behmer et al., 2005 ) and have been described in over 500 species from over 100 families ( Sarma, 2011 ). While metal accumulators are oft en adapted to soils with high concentrations of heavy metals, these metals not only negatively aff ect the growth of intolerant species but can also cause abnormalities in their gamete and embryo development ( Sabrine et al., 2010 ; Mohsenzadeh et al., 2011 ). Moreover, direct exposure to some heavy metal ions (e.g., Ni) can inhibit pollen germination and pollen tube growth, leading to decreased seed production ( Malan and Farrant, 1998 ; Tuna et al., 2002 ; Breygina et al., 2012 ). "
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    • "In areas rich in nickel, various abnormalities of vegetative growth such as necrosis and chlorosis of leaves, reduction of biomass were also found (Yusuf et al. 2011). Nickel and other heavy metals can also affect plant reproduction because of anomalies in gamete development, embryogenesis, seed production (Mohsenzadeh et al. 2011) and polar cell growth (Breygina et al. 2012). "
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    • "Furthermore, it is unknown whether most serpentine plants accumulate Ni into pollen grains, despite evidence that plants growing in soils contaminated by metals via human activities can accumulate them into pollen (Moronét al. 2012). Metals in pollen could reduce germination (citations above; Mohsenzadeh et al. 2011; Yousefi et al. 2011a) or pollinator attraction (Meindl and Ashman 2014), and Ni accumulation in nectar can affect pollinator foraging (Meindl and Ashman 2013, 2014). Thus, a first and necessary step towards understanding the reproductive consequences of growth on serpentine soil is documenting metal concentrations of reproductive organs and floral rewards of non-hyperaccumulating serpentine plants, as well as determining whether or not nonhyperaccumulating endemic species are better able to avoid potentially deleterious effects of metals by excluding them from reproductive organs than nonendemics . "
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