CHEMISTRY & BIODIVERSITY – Vol. 11 (2014)
425
microcapillary) on a piece of filter paper attached (by double-sided adhesive tape) to the inner side of the
cover of the Petri dish. Up to 2 ml of compound and blank control were tested by this procedure. One ml of
essential oil per Petri dish was equivalent to 40 nl/ml. Each amount was tested in three replicates. After
incubation, the numbers of germinated seeds were counted, and the length of each radicle was measured.
The parameter to consider radical emergence as germinated is described in [4]; seeds with a protrusion of
non-differentiated cells without radical emergence were considered not germinated. Since compounds
inhibit both germination and growth, the effect of each compound on wheat seedlings was studied. The
amount of essential oil required to cause 50% inhibition of germination was determined, as described in
[
4], by interpolation from the curve obtained by plotting the means of the replicates vs. the amount of
essential oil applied.
Bioconversion of Compounds. Wheat seeds (Triticum aestivum L. cv Dariel) were germinated in 25-
ml glass vials, on three layers of filter paper (Whatman No. 1) wetted with 1.5 ml of dist. H O. Vials
2
containing 20 seeds each were incubated at 278 in the dark. Different paths of the bioconversion were
tested; in shortage of O (the vials were closed hermetically), in abundance of O (opening and closing
2
2
the vials every 3 h), and with N . To test the bioconversion of the each compound, a known amount of
2
every examined monoterpene was loaded (using a calibrated glass microcapillary) on a piece of filter
paper, which was attached to the inner side of the cover of the vial. Amounts of up to 4 ml of compound
were applied in this way. The compound per vial (1 ml) was equivalent to 40 nl/ml. Experiments were
t
conducted in five replicates. After 24 h, seeds were extracted with BuOMe, and the embryo and the
endosperm were separated.
Determination of Compounds in the Seed. The examined monoterpenes were (þ)-(R)-citronellal,
(
ꢀ)-(S)-citronellal, (þ)-(R)-citronellol, (ꢀ)-(S)-citronellol, (þ)-(R)-citronellic acid, and (ꢀ)-(S)-
citronellic acid. Seeds were washed by mild shaking for 5 s in dist. H O. Then, an extraction with
2
t
BuOMe containing 10 mg/ml isobutylbenzene as an internal standard was performed for 24 h with gentle
shaking at r.t. The samples were analyzed with a GC/MS 7890A apparatus equipped with a Hydrodex-b-
6
-TBDM (MACHERY-NAGEL, DE-Dꢂren), 25 mꢁ0.25-mm fused silica-gel cap. column; He was used
as the carrier gas; injection temp. was 2308, and the transfer line temp. was 2308. Column conditions were
08 for 10 min, followed by 1.58/min to 1308 and 108/min to 2008. The components were identified by co-
4
injection with authentic samples and by comparison of the EI-MS data obtained from computerized
libraries.
REFERENCES
[
[
[
[
1] L. A. Weston, Agron. J. 1994, 36, 860.
2] S. O. Duke, F. E. Dayan, J. G. Romagni, A. M. Rimando, Weed Res. 1999, 40, 99.
3] S. S. Narwal, Allelopathy J. 2010, 25, 51.
4] N. Dudai, A. Poljakoff-Mayber, A. M. Mayber, E. Putievsky, H. R. Lerner, J. Chem. Ecol. 1999, 5,
1079.
[
[
[
5] S. Kordali, A. Cakir, S. Sutay, Z. Naturforsch., C 2007, 62, 207.
6] S. O. Duke, Allelopathy J. 2010, 25, 17.
7] N. Dudai, A. Poljakoff-Mayber, H. R. Lerner, E. Putievsky, U. Ravid, E. Katzir, Acta Hortic. 1993,
3
44, 123.
8] N. Dudai, D. Chaimovitsh, O. Larkov, R. Ficsher, Y. Blaicher, A. M. Mayer, Plant Soil 2009, 314,
11.
[
[
3
9] N. Dudai, O. Larkov, E. Putievsky, H. R. Lerner, U. Ravid, E. Lewinsohn, A. M. Mayer,
Phytochemistry 2000, 55, 375.
[
[
[
10] A. L. Crowell, D. C. Williams, E. M. Davis, M. R. Wildung, R. Croteau, Arch. Biochem. Biophys.
2002, 405, 112.
11] Y. Iijima, R. Davidovich-Rikanati, E. Fridman, D. R. Gang, E. Bar, E. Lewinsohn, E. Pichersky,
Plant Physiol. 2004, 136, 3724.
12] C. Landmann, B. Fink, M. Festner, M. Dregus, K.-H. Engel, W. Schwab, Arch. Biochem. Biophys.
2007, 465, 417.