Influence of Nerium oleander L. Leaves on Soil Microbial Populations and Enzyme Activities

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2nd_{Interna onal Mediterranean Science and Engineering Congress (IMSEC 2017)}

Çukurova University, Congress Center, October 25-27, 2017, Adana / TURKEY Pages: 1719-1719, Paper ID:761

1719

(*) Corresponding author

Infl uence of Nerium oleander L. Leaves on Soil Microbial

Populations and Enzyme Activities

Seçil Berna Kuzu

1*

_{, Burak Koçak}

1

_{, Şahin Cenkseven}

2

_{, Damla Sihay}

1

_,

Hatice Korkmaz Güvenmez

1

_{, Cengiz Darıcı}

1

Abstract

Nerium oleander L. (Common oleander, Apocynaceae) is an ornamental shrub in Mediterranean Region and all parts of this plant were toxic as it was reported in previous. In ten decades, many reports showed that this toxic plant have also antimicrobial and antifungal compounds. Th us, it has become essential to investigate the eff ects of oleander leaves on microbial populations and their enzyme activities in soil. Eff ects of oleander leaves on soil microbial populations (total aerobic bacteria and fungi) and enzyme (cellulase and xylanase) activities were determined under diff erent moistures in present study. Oleander soils were taken from Cukurova University Campus in February 2014. Some soil physical and chemical properties with leaf carbon and nitrogen contents were determined. Soils were mixed with oleander leaves at doses of half (L0.5), same (L1) and double (L2) of soil organic carbon content and humidifi ed at their 80% and 60% of fi eld capacities (80%FC and 60%FC). Soils without oleander leaves humidifi ed at same fi eld capacities were used as controlled. All soils were incubated for 30 days at 28°C. Soil microbial populations and their cellulase and xylanase activities were measured on 15th_{and 30}th_{days of incubation. All doses of oleander increased soil}

microbial populations compared to controls under both fi eld capacities. Bacteria populations were highest at L1 dose on 15th_{days and at L0.5 dose on 30}th_{days under both FC. Same L1 and L0.5 doses were signifi cantly}

higher than controls (p<0.05). Fungi populations were generally increased as Oleander leaf doses increased in all days under both FC. Fungi was highest at L1 dose on 15th_{days and L2 dose on 30}th_{days under both}

FC. In general, these same doses signifi cantly increased fungi populations compared to controls (p<0.05). It was expected that as soil moisture decreased, soil microbial population would decrease in this study. However, eff ects of fi eld capacities on soil aerobic bacteria were variable but fungi under 80%FC was generally higher than 60%FC in all doses. One of the main results in microbial populations was that time was more dominant factor than fi eld capacity and leaf doses. Both soil bacteria and fungi populations were higher on 15th_{day than}

30th_{day. Soil enzyme activities were generally increased by all leaf doses. In general, highest enzyme activities}

were measured at L2 dose that was signifi cantly higher than control on both days and fi eld capacities (p<0.05). Previous studies showed that these enzymes play a key role in carbon cycling and microorganisms utilize carbon sources from plant residues to sustain their lives by using these enzyme systems. In present study, it’s clear that Oleander leaves not only have any negative eff ect on soil microbial populations and their enzyme activities but also have enhanced soil microbial activity. It’s suggested that these results would greatly enhance our understanding of which groups of microorganisms are directly accessing a given nutrient resource, thus providing greater information about the pathways by which energy and nutrients fl ow through the soil food web.

Th is study was funded by Cukurova University Scientifi c Research Projects Coordination Unit with project number: FEF2013BAP27.