8 Journal of Food Legumes 263 4, 2013
3.5 Reproductive biology: Pollen function
It has been found, that inhibitory effects of sulfur dioxide on pollen germination and tube elongation have occurred at
concentrations lower than those at which foliar effects have been recorded Varshney and Varshney 1980. This suggests
that heavy metals, even if present at low concentrations in plant tissue, may affect pollen germination and pollen tube
growth. Pollen tubes are excellent standard systems with which the effects of drugs and pollutants can be investigated
Kristen et al.1993. Studies report that heavy metals at toxic levels inhibit pollen germination, pollen tube growth Tuna
et al.
2002 by causing ultra-structural changes. Xiong and Peng2001tested 5 herb species Vicia augustifolia,
V.tetrasperma, Pisum sativum, Plantago depressa, and
Medicago hispida for their responses against Cd exposure
for pollen germination and tube growth to Cd exposure in vitro. Results revealed that pollen germination of all the species
was inhibited at Cd concentrations of 2.51µgml and higher, and tube growth was inhibited at concentrations of 1.58µgml
and higher. The pollen response to Cd stress exhibited interspecies differences. Vicia angustifolia and V. tetrasperma
were sensitive to Cd and were inhibited in either pollen germination or tube growth by Cd at 0.01 µgml. At 1 µgml,
pollen tube growth of V. angustifolia, V. tetrasperma, and P. sativum
was inhibited. Results suggested that cadmium at such a low concentration as 0.01 lgmL is able to exert adverse
effects on pollen germination in some sensitive species, while it fails to do so for less-sensitive species.
3.6 Phyto-hormones
Quantitative determination of endogenous chemical compounds including hormones in plants growing under
controlled environmental conditions in presence and absence of heavy metals is used to study the effect of heavy metals
Varga et al.1999. Atici et al. 2005 investigated the changes in abscissic acid, gibberellic acid, zeatin and zeatin riboside
hormones of chickpea seeds germinating under Pb or Zn heavy metals exposure. Pb increased abcisic acid and zeatin contents
while decreased gibbrellic acid content in the germinating seeds. High concentrations of Zn 1.0 and 10 mM decreased
contents of zeatin, zeatin riboside and giberellic acid while 0.1 mM Zn increased the content of the same hormones. ABA
content was enhanced by Zn in all concentrations used.Cakmak et al. 1989 estimated the concentrations of
phytohormones particularly IAA and concluded that its concentration in zinc-deficient bean Phaseolus vulgaris L.
plants are clearly lower compared to those of Zn-sufficient plantsZn
2+
, changes in concentrations of ABA are less distinct. Re-supply of Zn to deficient plants restores the IAA
level to that of the Zn-rich plants within 96 h, whereas the ABAconcentrations are only slightly increased after Zn
resupply.In contrast, the effect of Zn nutritional status oncytokinin levels is less clear. Information on effect of
phytohormones is sparse and is required to be worked out.
3.7 Adverse effects on nutritional value of legumes
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