Bosabalidis artemios michael glandular hairs, non-glandular hairs, and



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CONTENTS 
 
 
BOSABALIDIS ARTEMIOS MICHAEL – Glandular hairs, non-glandular hairs, and 
essential oils in the winter and summer leaves of the seasonally dimorphic Thymus 
sibthorpii (Lamiaceae)  ..................................................................................................  
3
 
SHARAWY SHERIF MOHAMED – Floral anatomy of Alpinia speciosa and Hedychium 
coronarium (Zingiberaceae) with particular reference to the nature of labellum and 
epigynous glands ...........................................................................................................  
13 
PRAMOD SIVAN, KARUMANCHI SAMBASIVA RAO – Effect of 2,6-
dichlorobenzonitrile (DCB) on secondary wall deposition and lignification in the 
stem of Hibiscus cannabinus L.................................................................................. 25 
IFRIM CAMELIA – Contributions to the seeds’ study of some species of the Plantago L. 
genus ..................................................................................................................................... 35 
VENUGOPAL NAGULAN, AHUJA PREETI, LALCHHANHIMI – A unique type of 
endosperm in Panax wangianus S. C. Sun ....................................................................  45 
JAIME A. TEIXEIRA DA SILVA – In vitro rhizogenesis in Papaya (Carica papaya L.) .......  
51 
KATHIRESAN KANDASAMY, RAVINDER SINGH CHINNAPPAN – Preliminary 
conservation effort on Rhizophora annamalayana Kathir., the only endemic mangrove 
to India, through in vitro method ...................................................................................  57 
JAIME A. TEIXEIRA DA SILVA – Smoke-saturated water from five grasses growing in 
Japan inhibits in vitro protocorm-like body formation in hybrid Cymbidium ...............  
63 
DUCA MARIA, GLIJIN ALIONA, ACCIU ADRIANA – The biological cycle of sunflower 
broomrape .....................................................................................................................  71 
BÎRSAN CIPRIAN, TĂNASE CĂTĂLIN, MARDARI CONSTANTIN – Variation of 
macromycetes species composition in two forest habitats from Giumalău Massif 
(Eastern Carpathians, Romania) ....................................................................................  
79 
PETRE CRISTIANA VIRGINIA, TĂNASE CĂTĂLIN – Description of the culture 
characteristics of some lignicolous Basidiomycetes species grown on three synthetic 
media .............................................................................................................................  105 
SELIMOV RESAD, IBADLI ORUC – In situ and ex situ conservation of rare and endangered 
geophytes of the Hirkan National Park (Azerbaijan) .....................................................  115 
MARDARI CONSTANTIN, OPREA ADRIAN, MÂNZU CIPRIAN, BÎRSAN CIPRIAN – 
The dwarf shrubs communities within Loiseleurio-vaccinietea Eggler ex Schubert 
1960 from Romanian Eastern Carpathians ....................................................................  121 
NAGODĂ EUGENIA, COMĂNESCU PETRONELA, ANASTASIU PAULINA – 
Phemeranthus confertiflorus: new alien species to Europe  ................................................. 
141 
DOMOKOS ERZSÉBET, CRISTEA VASILE – The woody vegetation in the middle stream 
of the Niraj Valley (Romania, Mureş County) ..............................................................  
149 
Aniversalia .................................................................................................................................  163 
In Memoriam  .............................................................................................................................  165 
Book Review .............................................................................................................................  167 
Guide to authors ........................................................................................................................  169 

BOSABALIDIS ARTEMIOS MICHAEL 
 
 
 
3
J. Plant Develop. 
20(2013): 3 – 11 
 
 
GLANDULAR HAIRS, NON-GLANDULAR HAIRS, AND 
ESSENTIAL OILS IN THE WINTER AND SUMMER LEAVES OF 
THE SEASONALLY DIMORPHIC THYMUS SIBTHORPII 
(LAMIACEAE)
 
 
BOSABALIDIS ARTEMIOS Michael
1
  
 
 
Abstract:   The structure and function of the glandular and non-glandular hairs, and also the yield and chemical 
composition of the essential oils in the winter and summer leaves of the seasonally dimorphic plant 
Thymus sibthorpii were studied. Glandular hairs comprise peltate hairs only (capitate hairs are 
missing). Peltate hairs are the sites of essential oil biosynthesis. They are more numerous in the 
winter leaves than in the summer leaves and consist of a 12-celled secretory head, a unicellular stalk, 
and an also unicellular epidermal foot. The essential oil of the winter leaves is mainly composed of 
linalool (42.4%), thymol (7.0%), p-cymene (5.8%), β-caryophyllene (5.7%), borneol (5.6%), and 
terpinen-4-ol (4.8%). The oil of the summer leaves is principally constituted of p-cymene (25.0%), 
linalool (19.1%), terpinen-4-ol (8.5%) and borneol (8.3%). Non-glandular hairs proliferate in the 
summer leaves. They are conical in shape and consist of one basal epidermal cell and one apical 
pointed cell. Glandular and non-glandular hairs are implicated in the chemical and mechanical 
defense of the plant, respectively. 
 
Keywords: 
 
anatomy, leaf hairs, Thymus sibthorpii. 
 
Introduction 
 
The aerial organs of many plants are covered with hairs which exhibit a great 
diversity in shape, size, structure and function. According to WEISS’s (1867) definition, 
plant hairs are structures which owe their origin to outgrowths of single epidermal cells, 
eventually accompanied by divisions. Similarly, UPHOF (1962) considers that the name 
“trichome” should be applied to all outgrowths of the epidermis of leaves, shoots and roots, 
no matter whether they are unicellular or pluricellular. The distinction of plant hairs into 
“glandular” and “non-glandular” which is largely used today, has its origination to 
SOLEREDER (1908). 
 
The functional role of plant hairs is multifarious. Non-glandular hairs were found 
to have an implication in reduction of transpiration and leaf overheating, and also in 
protection from UV-B radiation [MANETAS, 1999]. Their principal role, however, is 
mechanical protection against various predators, and particularly the insects (obstacles in 
insect movement, feeding, and oviposition on leaves) [GOERTZEN & SMALL, 1993]. 
Glandular hairs, on the other hand, exert chemical protection by secreting different kinds of 
secondary metabolites which may be repellent and lethal to insects, skin irritant and 
deleterious to mammals, and toxic to microorganisms [ROSENTHAL & BERENBAUM, 
1991; AZAZ & al. 2004]. 
                                                 
1
 Department of Botany, School of Biology, Aristotle University, Thessaloniki 54124 – Greece. E-mail: 
artbos@bio.auth.gr 

GLANDULAR HAIRS, NON-GLANDULAR HAIRS, AND ESSENTIAL OILS IN THE WINTER… 
 
 
4
 
The objectives of the present work comprised determination of the types of 
glandular and non-glandular hairs in Thymus sibthorpii and examination of their anatomy, 
in order to compare them with other Thymus species. Moreover, the size, density 
distribution, and morphometry of the hairs, as well as the chemical constitution of the 
secreted essential oils were studied in winter and summer leaves in an attempt to find out 
whether low and high temperatures have any possible effects on these parameters. The 
obtained data would provide useful information to taxonomists dealing with plant hairs, and 
also to ecologists working on plant adaptation.  
 
Materials and methods 
 
Plant material and sampling 
        
Native  plants  of  Thymus sibthorpii Bentham (Lamiaceae) were studied in the 
region of Ormylia, Chalkidiki, N. Greece (N 40
°16'53", E 23°31'43", altitude 51m a.s.l.). In 
this region, the meteorological data in the three years of study (2009-2011) showed that 
during the winter months the average daily air temperature was 7.3 
°C, the average daily 
relative air humidity 78.0%, and the average daily rainfall 1.9 mm. During the summer 
months, the climatic conditions were mild (not hot and dry) with an average daily air 
temperature of 24.3 
°C, an average daily relative air humidity of 63.3%, and an average 
daily rainfall of 1.0 mm. Meteorological data were provided by the Regional Center for 
Plant Protection and Quality Control, Thermi, Thessaloniki, Greece. Winter sampling was 
performed in January and summer sampling in July. Fully-expanded leaves of annual 
shoots were used (3
rd
 node from the shoot basis). 
Microscopy 
     
From a sample of 18 leaves (3 leaves x 6 plants), 5 leaves were randomly selected 
for light microscopy (LM), and another 5 leaves for scanning electron microscopy (SEM). 
Leaves for LM were cut into small pieces which were subsequently fixed for 3h with 5% 
glutaraldehyde in 0.05 M phosphate buffer (pH 7.2). After washing in buffer, the specimens 
were post-fixed for 4h with 2% osmium tetroxide, similarly buffered. Samples were then 
dehydrated in an ethanol series (50-100%) and finally embedded in Spurr’s resin. Semithin 
sections (1 μm thick) of plastid embedded tissue were obtained with a Reichert Om U
2
 
microtome (Reichert Optische Werke AG, Vienna, Austria), stained with Toluidine Blue O 
and photographed on a Nikon Eclipse ι80 light microscope (Nikon Instruments, Amstelvee, 
The Netherlands). For SEM, the specimens, after fixation and dehydration, were critical-
point dried in a Balzers CPD 030 device (Balzers Union AG, Liechtenstein) and then 
carbon-coated in a Jeol JEE-4X vacuum evaporator. Observations were made with a Jeol 
JSM 840-A scanning electron microscope. 
Morphometry 
        
The densities (No/mm
2
) of the glandular and non-glandular hairs on both surfaces 
of the winter and summer leaves were determined using 36 SEM micrographs. These 
micrographs were also used for conducting morphometric assessments on the hairs. 
Essential oils 
        
Leaf material was air-dried at room temperature and then grossly pulverized and 
subjected to hydrodistillation for 2h using a modified Clevenger-type apparatus. The oil 
content was expressed in ml/100 g leaf dry weight. Essential oil analyses were performed 
on a Shimadzu GC-2010-GCMS-QP 2010 system operating at 70eV. This was equipped 
with a split/splitless injector (230 
°C) and a fused silica HP-5MS capillary column (30 m x 

BOSABALIDIS ARTEMIOS MICHAEL 
 
 
 
5
0.25 mm i.d., film thickness 0.25 μm). The temperature program ranged from 50 
°C to 290 
°C, at a rate of 4 
o
C/min. Helium was used as a carrier gas at a flow rate of 1.0 ml/min. 
Injection volume of each sample was 1 μl. Arithmetic indices for all compounds were 
determined using n-alkanes as standards [VAN DEN DOOL & KRATZ, 1963]. Relative 
percentage of separated compounds was calculated from total ion chromatogram by a 
computerized integrator. The identification of the components was based on comparison of 
their mass spectra with those of NIST21 and NIST107 [MASSADA, 1976], and on 
comparison of their arithmetic indices with literature data [ADAMS, 2007]. Essential oils 
were often subjected to co-chromatography with authentic compounds (Fluka, Sigma). 
Statistics 
Statistical analysis was performed with the SPSS package (SPSS Inc. Chicago, 
USA) using ANOVA for comparison of means between treatments. Significance was 
determined at p≤0.05 probability level.
 
 
Results  
 
Thymus sibthorpii plants have an entirely different appearance in winter and 
summer (Fig. 1A, B), a fact principally due to the different environmental conditions 
prevailing in each of these seasons. Thus, winter plants (Fig. 1A) compared to summer 
plants (Fig. 1B) are greatly smaller, with shorter densely-arranged shoots and shorter, dark-
green leaves. Scanning electron microscopy disclosed that both the winter and summer 
leaves bear on their surfaces glandular and non-glandular hairs (Fig. 1C). Glandular hairs 
consist of essential oil-secreting peltate hairs only (Fig. 1C, large asterisks) with no 
presence of capitate hairs. Peltate hairs are more numerous in the winter leaves (Tab. 1) and 
they are constructed of a 12-celled secretory head (Fig. 2B), a unicellular stalk and an also 
unicellular epidermal foot. The 12 head cells are arranged in such a manner that 4 small 
cells are located in the centre of the head and 8 large ones in the periphery. The foot cell is 
radially surrounded by 13-15 elongated epidermal cells (Fig. 2C). Non-glandular hairs 
proliferate in the summer leaves and particularly on their upper side (Tab. 1). They are of 
one type only, i.e. short conical structures covered with granula (Fig. 1C, small asterisks; 
Fig. 2D). Their size (height, thickness) does not appear to differ between the winter and 
summer leaves. Anatomically, non-glandular hairs are composed of one large basal cell 
located at the level of the epidermis and one pointed cell sited above it (Fig. 2E). 
      
Comparative quantitative analyses of the leaf essential oils in T. sibthorpii showed 
that the winter leaves have a higher essential oil yield (1.20%, i.e. 1.20 ml /100 g leaf d.w.) 
compared to the summer leaves (1.11%) (Tab. 2). Qualitative analyses of the winter and 
summer oils disclosed the existence of 49 compounds accounting for 97.6-99.3% of the 
total oils (Tab. 2). Both types of oils contain as principal components p-cymene, linalool, 
borneol, terpinen-4-ol, thymol, and β-caryophyllene. The major constituent of the winter oil 
is linalool (42.4%), followed by thymol (7.0%), p-cymene (5.8%), β-caryophyllene (5.7%), 
borneol (5.6%) and terpinen-4-ol (4.8%). The major constituent of the summer oil is p-
cymene (25.0%), followed by linalool (19.1%), terpinen-4-ol (8.5%) and borneol (8.3%). 
Thymol and β-caryophyllene occur at a low percentage (about 1%).
 
 
 
 

GLANDULAR HAIRS, NON-GLANDULAR HAIRS, AND ESSENTIAL OILS IN THE WINTER… 
 
 
6
 
 
 
Fig. 1. Thymus sibthorpii. Lateral view of herbarium material of winter plant (A) and summer plant 
(B). Compare the size and density of shoots and leaves. C. SEM view of the leaf surface with peltate 
glandular hairs (large asterisks) and conical non-glandular hairs (small asterisks). Bar in μm. 
 
 
 
 
 
 
 
 

BOSABALIDIS ARTEMIOS MICHAEL 
 
 
 
7
Fig. 2. A. SEM view of a peltate hair. B. Paradermal section of the head of a peltate hair. The head 
consists of 12 cells. C. Paradermal section of the foot cell (fc) which appears radially surrounded by 
13-15 elongated epidermal cells. D. Non-glandular hairs as they appear in SEM. E. Longitudinal 
section of non-glandular hairs composed of a large basal epidermal cell and a small apical pointed 
cell. Bars in μm. 
 
Discussions 
 
SEM observations on the blade surfaces of the winter and summer leaves of 
Thymus sibthorpii revealed the presence of numerous peltate glandular hairs and the 
absence of capitate glandular hairs. SATIL & al. (2005) also reported a rare presence of 
capitate hairs in the leaves of T. migricus. However, studies on T. malyi, T. vulgaris and T. 
capitatus  mentioned the existence of capitate glandular hairs with a unicellular head 
[WERKER & al. 1985; MARIN & al. 2008; BOZ & al. 2009]. The peltate hairs in T. 
sibthorpii appeared to consist of a secretory head with 12 cells. The number of head cells in 
the peltate hairs of other Thymus species was found to fluctuate, as in T. capitatus where 
the head consisted of 14 cells [WERKER & al. 1985], in T. serpyllum of 8 cells [UPHOF, 
1962], in T. vulgaris of 8-12 cells [YAMAURA & al. 1992] and also of 10-14 cells 
[BRUNI & MODENESI, 1983], and in T. malyi of 8 cells [MARIN & al. 2008]. The 
peltate hairs and specifically their head cells are the only cells from all leaf tissues which 
possess the necessary enzymic equipment for essential oil biosynthesis [McCASKILL & al. 
1992]. Thus, the higher the number of peltate hairs on leaves is, the higher the amount of 
the essential oil derived by distillation. This is in accordance with the morphometric 
assessments on T. sibthorpii in which the higher number of peltate hairs on winter leaves 
compared to summer leaves resulted in a higher essential oil yield. 

GLANDULAR HAIRS, NON-GLANDULAR HAIRS, AND ESSENTIAL OILS IN THE WINTER… 
 
 
8
      
The elongated epidermal cells which radially surround the foot cell of each peltate 
hair (peribasal cells) are considered as a fundamental accessory of the hair. Thus, the large 
surface area defined by the radial arrangement of the peribasal cells, their convergence 
towards the foot cell, and their location at the border with the mesophyllic photosynthetic 
parenchyma, favour the interpretation that peribasal cells collect from the mesophyll 
photosynthates which become centripetally transferred first to the foot cell (large central 
vacuole) and then to the apical head cells. There, they will constitute the precursors for the 
biosynthesis of the essential oil.  
      
Qualitative analysis of the essential oils from T. sibthorpii winter and summer 
leaves showed that in both types of oils the major components are linalool and p-cymene. 
Linalool dominated in the winter leaves and p-cymene in the summer leaves. The high 
content in linalool of the thyme oil is ascribed by VERNET & al. (1986) to the low 
environmental temperatures (winter conditions). In accordance to our results, high contents 
of p-cymene, γ-terpinene, borneol, and terpinen-4-ol were also recorded by VOKOU (1993) 
in the oil of the summer leaves of T. capitatus. 
 
 
Tab. 1. Thymus sibthorpii. Morphometric assessments of peltate glandular hairs and 
conical non-glandular hairs in fully expanded leaves of winter and summer (±SD, n=36). 
Means between columns with different letters are significantly different at 0.05 level 
                                                                       Winter leaves                                 Summer leaves 
Density of peltate glandular 
hairs on the upper leaf side 
(No/mm
2

 
Density of peltate glandular 
hairs on the lower leaf side 
(No/mm
2

 
Head diameter of peltate 
glandular hairs in surface view 
on the upper leaf side (μm) 
 
Head diameter of peltate 
glandular hairs in surface view 
on the lower leaf side (μm) 
 
Density of conical non-
glandular hairs on the upper 
leaf side (No/mm
2

 
Density of conical non-
glandular hairs on the lower 
leaf side (No/mm
2

 
Thickness of the base of 
conical non-glandular hairs on 
the upper leaf side (μm) 
 
20.7±2.9 a 
 
 
 
8.8±0.3 a 
 
 
 
75.9±6.5 a 
 
 
 
71.7±5.7 a 
 
 
 
149.6±17.6 a 
 
 
 

 
 
 
26.5±2.3 a 
 
 
12.8±2.1 b 
 
 
 
7.7±0.4 b 
 
 
 
85.4±9.1 b 
 
 
 
82.6±8.5 b 
 
 
 
164.5±19.3 b 
 
 
 
62.6±5.3 
 
 
                      
27.1 ±3.0 a 
 

BOSABALIDIS ARTEMIOS MICHAEL 
 
 
 
9
 
Thickness of the base of 
conical non-glandular hairs on 
the lower leaf side (μm) 
 
Height of conical non-
glandular hairs on the upper 
leaf side (μm) 
 
Height of conical non-
glandular hairs on the lower 
leaf side (μm) 
 
 
 

 
 
                
39.8 ±5.7 a 
 
 
 

 
 
10.1±2.2 
 
 
                       
40.2±8.6 a 
 
                 
 
18.3±7.8 
*There are no non-glandular hairs on the lower leaf side of the winter leaves 
 
Tab. 2. Thymus sibthorpii. Qualitative and quantitative compositions (%) of the essential 
oils from winter and summer leaves 
Components
 a
 AI
 b
 
Winter 
leaves 
Summer 
leaves 
Identification 
c
 
 
 
 
 
 
α-Thujene 926 
n.d. 
0.4 
AI, 
MS 
α-Pinene 
932 
n.d. 
1.0 
AI, MS, Co-GC 
Camphene  
946 
0.2 
1.7 
AI, MS 
Sabinene 972 
n.d. 
0.2 
AI, 
MS 
β-Pinene 
974 
n.d. 
0.3 
AI, MS, Co-GC 
1-Octen-3-ol 980 
1.0 
0.3 
AI, 
MS 
3-Octanone 988 
0.5 
0.4 
AI, 
MS 
β-Myrcene 
991 
0.1 
0.2 
AI, MS, Co-GC 
3-Octanol 997 
0.6 
0.2 
AI, 
MS 
α-Phellandrene  
1002 
n.d. 
0.3 
AI, MS 
α-Terpinene 1017 
0.5 
1.7 
AI, 
MS 
p-Cymene 


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