عنوان مجله
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PLANT SYSTEMATICS AND EVOLUTION
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چکیده
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The genus Mentha is a taxonomically complex
genus, characterized by large morphological variations.
Only a few, frequently overlapping, characters are of value
in taxonomy. Comparative floral developmental studies
provide an opportunity for better understanding the systematic
relationships among different species. The inflorescence
and floral ontogeny of three Mentha L. species
(M. piperita L., M. pulegium L. and M. suaveolens Ehrh.)
were investigated using epi-illumination light microscopy.
All three species studied have thyrses with the same
developmental pathway. The lack of higher order bracts
and the monochasial branching of the higher order inflorescence
apices were found as special features of inflorescence
ontogeny. Sepals appear unidirectionally from the
adaxial side in all except for M. pulegium which shows a
modified unidirectional sequence. Variable sequences of
petal and stamen appearance from unidirectional to
reversed unidirectional sequence are present in all. Significant
ontogenetic features include (1) appearance of the
corolla as a rim before petal lobes become visible and (2)
instability in petal aestivation. Morphological features
including densely hairy calyx, five-lobed corolla tube,
smaller adaxial stamens and hairy ovary with included
style distinguish M. pulegium from the other species. On
the basis of our results floral ontogenetic features could be
considered important characters for delimiting or diagnosing
different sections in the genus Mentha. Variable
sequences of petal lobe appearance and instability in petal
aestivation were found as unusual developmental
characters.
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