Different aspects of inhibition of growth and photosynthesis of maize (Zea mays L.) by the phosphonate herbicide sulphosate, 3: Effect of plant age
2007
Nikolic, B., Institute for Plant Protection and Environment, Belgrade (Serbia) | Drinic, G., Maize Research Institute Zemun Polje, Belgrade - Zemun (Serbia) | Jovanovic, V., Institute of Pesticides and Environmental Protection, Belgrade (Serbia) | Janjic, V., Institute of Pesticides and Environmental Protection, Belgrade (Serbia) | Markovic, A., Faculty of Sciences, Kragujevac (Serbia)
The effects of the herbicide sulphosate on the growth, accumulation and allocation of dry weight and photosynthesis in maize plants of different age (5, 6, and 7 weeks) were investigated. Dry weight accumulation (ln DW), which ultimately determines growth, was found to correlate highly significantly with root volume (Vr) and stem mass ratio (SMR) in maize plants aged 5 and 7 weeks, while in plants aged 6 weeks a highly significant correlation was found with root mass ratio (RMR) and leaf mass ratio (LMR). Besides, plants aged 6 weeks had a significantly higher content of chlorophyll a (Chla) in the youngest fully developed leaves, compared to plants aged 5 and 7 weeks. Based in these findings, we assumed there was also a difference between plants in these age groups in terms of the reaction of their photosynthetic systems to stress caused by herbicide sulphosate. Regulation of photosynthesis in the sulphosate-stressed maize plants aged 5 and 7 weeks is thus most probably independent of photosystem 2 (PS II), which is consistent with literature data on the activity of that herbicide. On the other hand, photosynthesis in the sulphosate-stressed maize plants aged 6 weeks is regulated by non-photochemical quenching of Chla fluorescence (whose indicator is NPQ). It is an optimal way through acclimation for regulating photosynthesis under stress. Taking also into consideration the factors that determine dry weight accumulation in maize plants aged 6 weeks, we should not disregard the possibility that photosynthesis in maize plants of that age group may be regulated by changes in the source-sink ratios.
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