Peltate Glands Research Articles

Comparative taxonomy and evolutionary significance of foliar epidermis in Jasminum L. (Oleaceae) based on light and scanning electron microscopy

Jasminum L. is an important genus of the Oleaceae family with nearly 200 species cultivated or distributed wild in almost all parts of the world. A comparative taxonomy and evolutionary relationship on the basis of foliar epidermal quantitative and qualitative micro-morphological characters of nine species of the genus Jasminum were assessed using light microscopy (LM) and scanning electron microscopy (SEM) techniques. Foliar epidermal anatomical attributes like number and size of cells, stomata, stomata complex, granular and non-granular trichomes along with the abaxial to adaxial cell ratio and stomata index were assessed as distinguished characters of the Jasminum foliar epidermis. Results displayed irregular types of cells, anomocytic, cyclocytic, anisocytic and giant stomata, peltate glands and unicellular or uniseriate trichomes in Jasminum species. The presence of domatia at the vein axil, glabrous, hairy, or spiny leaf margin, midrib, anticlinal view of the cells, cuticular folds and striations appeared as valuable micro-morphological attributes in Jasminum. The cluster analysis based on micro-morphology divided Jasminum species into two major clusters. The first cluster (C1) displayed four white flowering Jasminum species from section Unifoliolata with shared characters like simple opposite leaves with spinose and cuticular striations. The second cluster (C2) showed five white and yellow flower-bearing Jasminum species having compound leaves with cuticular folds or striations and spinose at their leaf margins. Conclusively, micro-morphological attributes are crucial to characterize and infer evolutionary relationships and the direction of character evolution from yellow to white flowering Jasminum.

Traditional knowledge and field marker development for essential oil content using peltate gland trichome and leaf colour in basil (Ocimum basilicum L.)

Twenty-six accessions of sweet basil obtained from different parts of India were evaluated for morphological and quantitative characters. These accessions were observed for distinguish characters like trichome type, peltate gland (PG) size, sepal and flower colour, stem girth, branching pattern, growth habits and leaf colour. Besides that, they were observed for yield contributing characters viz., maximum plant height, spread, stem girth, fresh leaf, dry leaf, herbage yield and essential oil yield, and DOB-8W was found superior as compared to checks. Maximum number of peltate glands (PG) on abaxial leaf surface as compare to adaxial were recorded at all the three stages (young, mature and old based on leaf position on axis). However, PGs formation takes place only in younger leaves, therefore, the numbers of PGs were reduced in mature and older leaves due to expansion of leaf area with progression of age. Number of PGs on abaxial surface of young leaf, green leaf colour and essential oil content had positive relationship with each other. The green and purple colour intensity in leaf is to be field notch for initial screening of accessions for essential oil content.

Improving salinity tolerance in Salvia officinalis L. by foliar application of salicylic acid

BackgroundHigher absorption and translocation of sodium (Na) and chlorine (Cl) ions in plant tissue can lead to serious physiological and biochemical changes. However, salicylic acid (SA) is a natural signaling molecule responsible for the induction of environmental stress tolerance in plants. Spraying SA could provide protection against several types of stress such as salinity. This study aimed to show the influence of SA spraying (0.5 and 1 mM) on the damaging effects of NaCl toxicity (150 mM) in Salvia officinalis L. plants.ResultsThe results showed that salinity strongly inhibited the growth of aerial and root parts and this inhibition was accompanied by a significant decrease in the production of chlorophyll pigments (by 63%). There was also a significant accumulation of Na, mainly in the roots. This accumulation of Na+ ions was accompanied by a decrease of calcium (Ca), potassium (K) and phosphorus (P) concentrations. However, SA mainly at 0.5 mM, greatly improved plant growth, essential oils and chlorophyll pigments synthesis. Besides, SA led to a decrease in Na content and an improvement in Ca, K and P content in the leaves and roots. Salt stress decreased the essential oil yield from 1.2% (control) to 0.4% (NaCl). Furthermore, gas chromatography–mass spectrometry analysis of essential oils exhibited that the 1,8-cineol, α-thujone, and camphor were identified as the main components of essential oils under all treatments. However, we noted in stressed plant treated or not with SA the appearance of the new majority compound thujanone. Salt stress decreased the major compounds content. SA spray under stress condition increased the content of major compounds compared to stressed plants untreated with SA. The histological study in scanning electron microscopy showed the peltate glands density decreased strongly under NaCl toxicity. However, SA application on stressed plants increased peltate glands density. On the other hand, the glands of stressed plants often show certain anomalies in the morphology: the first anomaly observed was the presence of glandular structures characterized by deformations in the form of small protuberances located on the head of the gland. The second, a less common abnormality is the morphological change in certain glands that change from a spherical to an ovoid shape. On another hand, all these anomalies were not detected in stressed plants sprayed with SA. Therefore, the absence of these anomalies under the effect of SA showed the repairing effect of this growth regulator.ConclusionThe findings of the present work suggest that spraying of SA may be useful for improving the plant growth in NaCl-contaminated areas.

Taxonomic Characteristics of Vegetative Organs for Invasive Species of Reynoutria Hook.

Species of the genus Reynoutria Hook. were originally intentionally introduced from East Asia and in the twentieth century, three of them were successfully naturalized in Europe: R. sachalinensis (F. Schmidt) Nakai, R. japonica Houtt. and their cultigenous hybrid R. × bohemica Chrtek & Chrtkova, which arose in the secondary distributional range of the parent species. As the taxa of the genus Reynoutria bloom very late, in late September-October, the characteristics of their leaves – shape, and type of pubescence – are mainly used as diagnostic ones. Identification of the species is often difficult, so this paper aims to identify diagnostic characters of their leaves in the secondary distribution range. Spontaneous invasive populations in Luxembourg, the Czech Republic, and Russia have been investigated. Comparisons have been made with plants growing in the natural range in Japan. Morphological characters were studied using a Keyence VHX-1000E digital microscope and an LEO 1430 VP scanning microscope. R. sachalinensis was found to be well distinguished from other species by its larger leaves with a heart-shaped base and a non-retracted apex. On the underside of the leaf, there are long uniseriate filiform trichomes along the lateral veins or outside the veins and peltate glands with 4-, 6- or 8-cell heads. For R. × bohemica, the presence of unicellular conical trichomes on the midrib was found to be a diagnostic feature in plants growing in Middle Russia (but not always) and is not applicable to plants from Czech populations, from which this species was actually described! In the taxonomic description of R. japonica, it has been suggested that the maximum height of the shoots should be significantly reduced (from 3 m to 1 m), as in the natural range this taxon has prostrate shoots. Plants of the secondary range with tall shoots are likely to be really R. × bohemica hybrids. It has been suggested that in Eastern Europe R. japonica grows generally very rare and predominantly in culture, and the information about most plants from invasive populations described in the literature as R. japonica should in fact be attributed to the hybrid complex R. × bohemica.

Effect of salicylic acid foliar application on growth, glandular hairs and essential oil yield in Salvia officinalis L. grown under zinc stress

BackgroundGenerally, zinc (Zn) is an essential element and acts as a plant nutrient, but at higher concentrations, it is toxic. Higher uptake and translocation of Zn into plant tissues can cause serious physiological and biochemical alterations. However, salicylic acid (SA) is an endogenous regulator of growth and signaling molecule responsible for inducing environmental stress tolerance in plants. Therefore, spray application of SA could provide protection against several types of stresses such as Zn toxicity. In this context, the ameliorative effect of SA (0.5 and 1 mM) on Salvia officinalis L. under Zn stress (40 mM) was studied.ResultsZn stress decreased growth, chlorophyll content, essential oil yield and peltate glandular trichome density. This toxicity can be linked to a strong accumulation of Zn in the various parts of the plant. In addition, Zn stress disturbed nutrients assimilation (K, P and Ca). However, spray of SA, particularly at 0.5 mM improved all parameters studied under both Zn and normal conditions. The positive effects of SA under Zn stress condition may be due to the decrease of Zn accumulation in different parts of the plant. This decrease was accompanied by an increase in K, P and Ca content. In addition, the histological study of S. officinalis leaves showed the presence of two types of glandular hairs, the peltate and capitate glands. In the leaves of stressed plants, we noticed the presence of glands with deformations in the form of pockets in the number of one or more as well as the glands with an oval form. On the other hand, all these abnormalities glands were not detected in stressed plants that were sprayed with SA. Therefore, the absence of these anomalies under the effect of SA showed the remedial effect of this growth regulator.ConclusionThe findings of the present work suggest that spraying SA maybe useful for improving the plant growth in Zn-contaminated areas.

Effects of salicylic acid on growth, mineral nutrition, glandular hairs distribution and essential oil composition in Salvia officinalis L. grown under copper stress

Higher uptake and translocation of copper (Cu) into plant tissues can cause serious physiological and biochemical alterations. Salicylic acid (SA) is a well-known naturally occurring signaling molecule responsible for inducing environmental stress tolerance in plants. Therefore, spraying of SA could provide protection against several types of stresses such as Cu toxicity. In this sense, a pot study was conducted to find out whether spraying of SA (0.5 and 1 mM) could ameliorate the adverse effect of Cu toxicity (40 mM) in Salvia officinalis L. plants. The results showed that the Cu stress significantly decreased the stem and root growth, and it reduced the calcium (Ca), phosphorus (P) and potasium (K) content of leaves and roots. Besides, Cu stress increased essential oil yield by 16.66% as compared to control. On the other hand, SA spraying on stressed plants significantly improved stem and root growth and increased Ca, P and K content. This improvement was more pronounced at 0.5 mM SA concentration. The essential oil content also increased under treatment with SA, specially at 0.5 mM concentration, with 116.66% enhancement as compared to stressed plants (untreated with SA). The increase in essential oil yield under all treatments was associated with significant enhancement in the density of peltate glands, with a much higher density when SA was applied at 0.5 mM concentration in presence of Cu stress. The chemical composition of oil changed according to the treatment. Cu stress led to a reduction of 19% in oxygenated monoterpenes levels, mainly due to the decrease in the major compounds, α-thujone, camphor and 1.8-cineol. However, spraying SA on stressed plants led to the recovery of normal levels of these compounds.

Identification of Sweet Basil Accessions Rich in Herbage, Essential Oil, and Anethole Yield from India

ABSTRACTSixteen accessions of sweet basil obtained from different parts of India were studied for qualitative and quantitative characters. The highest oil percent in green herbage, essential oil yield, and anethole yield were recorded in DOB-1 at full bloom stage. DOB-1 leaves had the highest number of peltate glands (PG) at all three stages (young, mature, and old based on leaf position on axis); the lowest was observed in DOB-2. The number of PG and oil content were positively correlated; however, an inverse relationship was observed between leaf age and the number of PG. The extract from green herbage was compared for their chemical compositions through chemical profiling. The highest anethole were observed in DOB-1 at full blooming stage. Overall, the sweet basil accessions DOB-1 and DOB-5 were superior in herbage, oil, and anethole yield that can be used further in improvement programs.

Investigation of the black dots on leaves of Stictocardia species (Convolvulaceae) using anatomical and histochemical analyses

The presence of black dots in leaves and flowers has historically been regarded as a taxonomically useful character to distinguish Stictocardia Hallier f. from other genera in Convolvulaceae. However, the origin and structure of these dots are unknown and available data about them are unclear. This research investigated the morphology, anatomy, and histochemistry of the black dots in order to clarify their structure and possible functions for the species. Black dots were examined in Stictocardia beraviensis (Vatke) Hallier f. and S. tiliifolia (Desr.) Hallier f. as representative species of the genus. Leaves and flowers were studied using crosswise micro-sectioning, Scanning Electron Microscopy, clearing techniques, and histochemical screening. The results revealed that the black dots were multicellular head-like structures better defined as peltate glandular trichomes, usually secreting chemical compounds. The peltate glands were composed of 10–20 secretory cells with 1–2 basal cells and were sunken in pits in the petiole and both surfaces of the leaf blades, especially on the abaxial surface. They were also observed on the sepals and petals of the Stictocardia spp. Histochemistry for Stictocardia spp. indicated a positive reaction for the presence of pectin substances, polysaccharides, unsaturated lipids, terpenes and flavonoids. We believe that these glandular trichomes play an important role in protecting the plants from pests and herbivores.

Effect of arbuscular mycorrhizal fungi and water stress on ultrastructural change of glandular hairs and essential oil compositions in Ocimum gratissimum

BackgroundThe objective of this work is to study the influence of arbuscal mycorrhizal fungi (Glomus intraradices) and water stress on the ultrastructural change of basil glandular hair and also on the essential oil synthesis, especially on the isomerization of the two main compounds methyl chavicol and trans-anethole.ResultsThe results of this study show that mycorrhization increases the yield of essential oils, with a maximum recorded in mycorrhizal stressed plants (0.33%) and a minimum among non-mycorrhizal unstressed plants (0.22%). Oxygenated monoterpenes represent the main family of essential oils. Furthermore, the chemical composition of these essential oils changed under the condition in which the plant is. However, the main compound methyl chavicol was found to be at maximum concentration (93%) in mycorrhizal stressed plants and minimum in non-mycorrhizal stressed plants (84%). Contrariwise, its isomer trans-anethole reached the maximum (8%) among non-mycorrhizal non-stressed plants and minimum (2%) in non-mycorrhizal stressed plants.ConclusionOcimum gratissimum L. leaves showed the presence of two types of peltate glands: the first one with 4 secreting cells and the second with 8 secreting cells. The diameter of these glands changed with the hydric state of plants; in the absence of mycorrhization, stress causes a decrease in the extracellular cavity diameter of glandular trichomes and their deflation which would cause a concentration of essential oil in the glands.Graphical abstractEffect of arbuscular mycorrhizal fungi and water stress on essential oil yield and compositions by the change in some endogenous plant growth regulators and glandular hairs morphology and density in Ocimum gratissimum

Selection of superior Ocimum sanctum L. accessions for industrial application

Holy basil (Ocimum sanctum L.), a sacred medicinal plant in India is widely used in Indian and other international traditional medicinal systems. Eleven accessions of the plant have been characterized for 21 quantitative and qualitative traits and six essential oil components. Three different harvesting stages of accessions grown in western India were collected for selecting superior accessions with desirable morphological and chemical characters affecting yield and contributing traits for industrial use. The essential oil was extracted by hydro distillation and the characterized by gas chromatograph-mass spectrometry. The colour of the leaves, new branches and inflorescence varied from green to purple-green. The basil accession, DOS-1, resulted in maximum dry leaf recovery (230gkg−1), total chlorophyll content (1.25mgg−1), carotenoid content (8.5mgmL−1) and number of peltate glands. The oil content in green herbage was maximum in DOS-1 (50gkg−1), followed by DOS-3 (44gkg−1) at crop maturity. Maximum oil and eugenol yield was also observed in DOS-1 (73kgha−1 and 67kgha−1). Overall, DOS-1 accession was found superior for leaf recovery, oil yield and eugenol content and therefore, can be used further in crop improvement and commercial cultivation as a new selection.

Features of micromorphological structure of medicinal hyssop

Micromorphological peculiarities of the structure of vegetative and generative organs of Hyssopus officinalis were analyzed. The epidermis of H. officinalis reveals diacyctic stomata and external outgrowths: glandular and covering trichomes, as well as peltate essential oil glands. Capitate and bent indumentary (covering) trichomes occur on the stem, while on the leaves peltate glands, conical and bent uni- and multicellular trichomes were observed. On the calyx, in the midrib region, there are peltate glands while the ribs are densely covered with indumentary and glandular trichomes. The corolla’s adaxial surface is covered with long indumentary trichomes, with sparse peltate glands occurring on the margins. The highest density of essential oil peltate glands is found on the adaxial surface of the calyx upper lip (15.8±2.54 pcs./mm2) and on the leaf abaxial surface (13.6±2.40 pcs./mm2). Glands with the largest diameter (47.82±2.82 μm) are located on the leaf adaxial surface.

Anatomical features of leaf blade of Artemisia dracunculus L. (Asteraceae) during introduction in Zhytomyr Polissya

This article represents the results of anatomical research of the lamina of Artemisia dracunculus L. introduced in Zhytomyr Polissya. Both, upper and lower epidermises are covered with cuticle, stomata are oval and of anomocytic type. The lamina is amphistomatic. The trichomas of stellar form as well as simple conic hairs were determined both on adaxial and abaxial surfaces. Rounded multicellular peltate glands that are typical for Asteraceae family and glandular capitate conic trichomas which represent tissue of external secretion. Tissue of internal secretion is represented by idioblasts and containers of essential oils. A. dracunculus has dorsiventral structure mesophylle and vascular bundle of main rib of collateral type. Peltate glands, capitate conic trichomas, secretory cells and nonglandular trichomas could be used as taxonomic features as well as for determination of raw material of A. dracunculus. The presence of peltate glands and glandular capitated trichomas in large amounts confirm that A. dracunculus introducted in conditions of Zhytomyr Polissya could be used as a sufficient producer of essential oils.

Structure, function and secretory products of the peltate glands of Centrolobium tomentosum (Fabaceae, Faboideae)

The glandular structures of Centrolobium tomentosum Guill. ex Benth. have been little studied despite the economic importance of this species. We describe here the distribution, development, structure and ultrastructure of the secretory cells of the peltate glands found on the vegetative organs of this species. Stem apices and leaves in various stages of development were collected and prepared for examination by light, scanning and transmission electron microscopy. Chemical analyses and conventional histochemical tests to determine the chemical nature of the secretory products were also carried out. Peltate glands occur on aerial vegetative organs during their primary growth stage. These trichomes are structurally stable, persisting throughout the development of the organ. During the initial stages of the gland development, cell separation creates a central space that expands as secretions accumulate. Maximum secretion rates occur during this phase and the secreting cells characteristically have well developed smooth and rough endoplasmic reticulum, and high numbers of plastids and mitochondria. During the later stages of the secretory phase, the central cells show symptoms of cell death and are incorporated in to the secretions. At trichome maturity, the central space is delimited by a uniseriate epithelium. In addition to the resin, which is the main secretory product, an extensive three-dimensional carbohydrate matrix was observed that extended throughout the central space, apparently giving support to the resin droplets. The terpenic nature of the secretion was confirmed by thin-layer chromatography. Given the terpenic nature of the secretion and the permanence of trichomes throughout all phases of leaf development, it is postulated that the resin-secreting trichomes act to protect the plant against herbivores.

Glandular trichomes of Rosmarinus officinalis L.: Anatomical and phytochemical analyses of leaf volatiles

Rosmarinus officinalis is known for the production of volatile compounds used in medicinal and food preparations. Leaves of R. officinalis are densely covered with capitate and peltate glandular trichomes where biosynthesis of volatiles mainly occurs. This study aims to conduct a morphological assessment to identify anatomical characteristics of both leaves and trichomes, as well as a chemical analysis of leaf volatile compounds, using histochemistry and stem distillation extraction. Specifically, anatomical and chemical constituents of the secretory structures of R. officinalis leaves were investigated using light and scanning electron microscopy, in addition to gas chromatography. One peltate and three types of capitate glandular trichomes were observed on the leaves of R. officinalis. Histochemical tests showed positive reactions to lipophilic compounds for both capitate and peltate trichomes, with only a slight detection of terpenoids with carbonyl group in peltate glands. Gas chromatography revealed camphor (23.2%) as the main volatile compound, mostly accumulating in peltate glandular trichomes. This phytochemical study of volatile compounds, together with anatomical and histochemical analyses of R. officinalis leaves, demonstrated the importance of leaves as a center of volatile production in peltate and capitate trichomes, as well as the nature of volatile composition, which is involved in species survival.

Revision and Biogeography of Centrolobium (Leguminosae - Papilionoideae)

A taxonomic revision and biogeographic study of the genus Centrolobium (Leguminosae - Papilionoideae) is presented. Centrolobium includes important timber trees distributed disjunctly in seasonally dry tropical forests and rain forests in Central and South America, from Panama to south-eastern Brazil. It is characterized by large samaroid pods with a spiny seed case and an abundance of orange peltate glands covering the leaves and inflorescences. Taxonomic distinctions between some species of Centrolobium have been a source of confusion. Here, seven species are recognized: C. robustum, C. microchaete, C. tomentosum, C. ochroxylum, C. sclerophyllum, C. paraense, and C. yavizanum. Previously recognized varieties of C. paraense, C. paraense var. paraense and C. paraense var. orinocense, are not maintained. Phylogenetic analysis of DNA sequence data from the internal transcribed spacer region of nuclear ribosomal DNA and the plastid matK gene and trnL-trnF intron and spacer support the monophyly of the genus. Different molecular dating methods indicate that the Centrolobium crown group and lineages found to the west and east of the Andes diverged before the Pleistocene. Divergences between species occurring east of the Andes, particularly in Bolivia and south-eastern Brazil are more recent, but nevertheless unlikely to be explained by Pleistocene climatic changes.

Mathematical modelling of essential oil SFE on the micro-scale—Classification of plant material

This article reports the achievements of the micro-scale (secretory-structure-scale) mathematical modelling of essential oil isolation by supercritical carbon dioxide. Some new experimental and modelling results are presented. The improved model for the supercritical fluid extraction from the glandular trichomes (peltate glands) is introduced. According to the behavior of plant secretory structures during the extraction as well as according to the modelling results, plant material was classified according to the dominant resistance to mass transfer during the extraction process. External mass transfer was the rate limiting step in the extraction from plants with secretory ducts and secretory cavities of citrus family. In the case of extraction from secretory cells, internal diffusion was the rate limiting step. In the extraction from glandular trichomes, external mass transfer, as well as diffusion through the gland membrane influenced the process.

Morphology and histochemistry of the glandular trichomes of Lippia scaberrima (Verbenaceae).

Lippia scaberrima, an aromatic indigenous South African plant, with medicinal application, potentially has economic value. The production of essential oil from this plant has not been optimized, and this study of the chemico-morphological characteristics was aimed at determining the location of oil production within the plant. Furthermore, the locality of other secondary metabolites important in medicinal applications needed to be ascertained. This information would be useful in deciding the protocol required for isolation of such compounds. The morphology of the glandular trichomes was investigated using a combination of scanning electron and light microscopy. Concurrently, the chemical content was studied by applying various chemical reagents and fluorescence microscopy. Three types of trichomes were distinguished on the material investigated. Large, bulbous peltate glands containing compounds of terpenoid nature are probably the main site of essential oil accumulation. Small glands were found to be both peltate and capitate and fluorescent stain indicated the possible presence of phenolic compounds. The third type was a slender tapered seta with an ornamented surface and uniseriate base, and evidently secretory in nature. This study linking the chemical content and morphology of the glandular trichomes of L. scaberrima has contributed to the knowledge and understanding of secretory structures of Lippia spp. in general.

Supercritical carbon dioxide essential oil extraction of Lamiaceae family species: Mathematical modelling on the micro-scale and process optimization

Abstract In this paper the essential oil supercritical carbon dioxide extraction from leaves of Lamiaceae family species was studied. Recent investigations of Lamiaceae family essential oil storage have shown that most of the oil is found in peltate glandular trichomes on the leaf surface. The effect of supercritical CO 2 on the peltate glands was investigated by Scanning Electron Microscopy. It was observed that exposure to supercritical CO 2 led to disruption of the peltate glands and essential oil release. This phenomenon was used as a basic hypothesis of the mathematical model of the supercritical fluid extraction with CO 2 . The model was applied to simulate basil, rosemary, marjoram and pennyroyal supercritical CO 2 extraction on the existing experimental data. An average deviation from the experimental data was less than 0.83%. The model results indicated a possibility of a decrease in the supercritical CO 2 consumption by modified and optimized processing of Lamiaceae family herbaceous material.

Glandular hairs and essential oils in micropropagated plants of Salvia officinalis L.

Micropropagation of Salvia officinalis L. (the common sage) plants to verify their ability to produce the typical volatile oil is described. The morphology of the glandular hairs and the chemical composition of the essential oils from in vitro shoots and micropropagated plants have been studied. For comparative purposes, volatile constituents from field grown mother plants and derived rooted cuttings have also been analyzed. Peltate glands secreting essential oils were present on the regenerated plants. Correlation between the higher amounts of camphor in the oils from the micropropagated, compared to the mother plants, and the stage of development of the regenerated sage is discussed. Histological observations from plant material at different physiological stages clearly demonstrate the rejuvenation of the germoplasm in the in vitro regenerated plants, in agreement with the chemical data.

The Biochemical and Molecular Basis for the Divergent Patterns in the Biosynthesis of Terpenes and Phenylpropenes in the Peltate Glands of Three Cultivars of Basil

Surface glandular trichomes distributed throughout the aerial parts of sweet basil (Ocimum basilicum) produce and store monoterpene, sesquiterpene, and phenylpropene volatiles. Three distinct basil chemotypes were used to examine the molecular mechanisms underlying the divergence in their monoterpene and sesquiterpene content. The relative levels of specific terpenes in the glandular trichomes of each cultivar were correlated with the levels of transcripts for eight genes encoding distinct terpene synthases. In a cultivar that produces mostly (R)-linalool, transcripts of (R)-linalool synthase (LIS) were the most abundant of these eight. In a cultivar that synthesizes mostly geraniol, transcripts of geraniol synthase were the most abundant, but the glands of this cultivar also contained a transcript of an (R)-LIS gene with a 1-base insertion that caused a frameshift mutation. A geraniol synthase-LIS hybrid gene was constructed and expressed in Escherichia coli, and the protein catalyzed the formation of both geraniol and (R)-linalool from geranyl diphosphate. The total amounts of terpenes were correlated with total levels of terpene synthase activities, and negatively correlated with levels of phenylpropanoids and phenylalanine ammonia lyase activity. The relative levels of geranyl diphosphate synthase and farnesyl diphosphate synthase activities did not correlate with the total amount of terpenes produced, but showed some correlation with the ratio of monoterpenes to sesquiterpenes.