Constituents of Leonotis leonurus flowering tops

Phytochemical investigation of flowering tops of Leonotis leonurus, yielded a new diterpene ester, 1,2,3-trihydroxy-3,7,11,15-tetramethylhexadecan-1-yl-palmitate along with five known metabolites. The structures of all compounds were determined by spectroscopic methods including 1D- and 2D NMR spectroscopy. All the isolated compounds were evaluated for antimalarial, cytotoxicity and for antimicrobial activities. Antimalarial activity for luteolin 7-O-β-d-glucopyranoside (4) (IC₅₀ = 2.2 μg/mL for the D6 clone and 1.8 μg/mL for the W2 clone) was observed. Chloroquine and artemisinin were used as positive controls which showed IC₅₀ of 0.016 and 0.0048 μg/mL for the D6 clone, respectively, and IC₅₀ of 0.14 and 0.0047 μg/mL for the W2 clone, respectively. None of the compounds were cytotoxic to Vero cells up to a concentration of 4.76 μg/mL.     

Territoriality and changes in resource use by sunbirds at Leonotis leonurus (Labiatae)

Summary Leonotis leonurus was studied with the aim of characterising nectar quality and quantity, and of monitoring the sunbirds' response to the resource. The flowers produced high quality nectar in low quantities. Nectar quality remained constant during the day and averaged 23.4% sucrose equivalents (an energy content of 3.8j/l). Nectar production was highest during the morning when flow rates reached a peak of 3.3 l/h. L. leonurus was visited by four species of sunbirds. In 1977 there were 7.8 visits/h to the flowers. The clump was defended by a single Olive Sunbird (Nectarinia olivacea) who defended the flowers intra- and interspecifically. On one day the territorial bird obtained approximately 57.1 kJ from the Leonotis flowers and expended 5.4 kJ on defence and 13.6 kJ overall while on the territory. Territorial behaviour and intruder pressure was a function of resource availability. When Leonotis nectar levels were high intruder pressure was intense and the territorial bird employed long chases as a defence behaviour. When nectar levels desreased intruder pressure was lower, the territorial bird chased less and employed vocalisations as a relatively inexpensive form of territorial behaviour.In 1978 there was an abundance of nectar sources in the study area due to the late onset of the dry season. Sunbirds were not territorial at Leonotis and visiting rates were lower than in 1977, averaging only 1.7 visits per hour. Instead the sunbirds concentrated on contemporaneously flowering plant species, particularly Halleria lucida.     

Glandular trichomes and essential oil constituents ofCalamintha menthifolia (Lamiaceae)

Plant material ofCalamintha menthifolia was collected from two populations grown in the Vikos-Aoos area (NW. Greece). The structure and ontogeny of the glandular trichomes and the chemical composition of the secreted essential oil were studied. The leaves ofC. menthifolia have numerous glandular trichomes of three morphological distinct types: 1) glandular scales with a unicellular foot and stalk, and a 12-celled head, 2) glandular hairs with a unicellular foot and stalk, and a unicellular pear-shaped head and 3) glandular hairs with a unicellular foot, a bicellular stalk and a unicellular elongated head. Qualitative and quantitative GC-MS analyses of the essential oils revealed piperitone oxide as the main constituent in both populations. In the light of these results the relationships beweenC. menthifolia and other members of theSatureja group as well as its taxonomy are discussed.     

The Ultrastructure of Glandular Trichomes ofPhillyrea latifoliaL. (Oleaceae) Leaves

The anatomy and ultrastructure of glandular trichomes at differentdevelopmental stages were investigated inPhillyrea latifoliaL.leaves by transmission electron microscopy and histochemicaltechniques. The trichome consisted of a multicellular secretoryhead, a unicellular stalk and a collecting cell surrounded byepidermal cells and spongy mesophyll cells. There were numerousplasmodesmata across the cell walls of trichome cells, and especiallybetween the stalk cell and the collecting cell. The collectingcell and stalk cell contained few chloroplasts. Mitochondria,elements of the endoplasmic reticulum and small vacuoles wereabundant in the secretory cells. Crystals were present in thesecretory cells and the collecting cell, especially at the matureand senescent stages of trichome development. As the cuticle,which covered the secretory cells, did not show pores or perforations,it is proposed that secretion occurred by accumulation of productsin subcuticular spaces followed by diffusion through the cuticle.Callose accumulation was observed between the stalk cell andthe collecting cell of senescent trichomes, especially in salt-treatedplants. Trichome ontogeny was accelerated in salt-treated plants.Copyright1998 Annals of Botany Company Cuticle;Phillyrea latifolia; secretion; transmission electron microscopy; trichome development.     

Glandular Trichomes ofCalceolaria adscendensLidl. (Scrophulariaceae): Histochemistry,Development and Ultrastructure

This paper reports the results of a study of the morphology and development of glandular trichomes in leaves ofCalceolaria adscendensLidl. using light and electron microscopy. Secretory trichomes started as outgrowths of epidermal cells; subsequent divisions gave rise to trichomes made up of a basal epidermal cell, a stalk cell and a two-celled secretory head. Ultrastructural characteristics of trichome cells were typical of terpene-producing structures. Previous phytochemical studies had revealed thatC. adscendensproduces diterpenes. Comparison withC. volckmanni,which produces triterpenes, and has trichomes with eight-celled secretory heads, suggests that there could be a relationship between the type of glandular trichome and the class of terpene produced. Further work is needed to test the hypothesis and to develop trichome characters as taxonomic tools.     

气孔在四季秋海棠营养器官和繁殖器官上的发育及相关性分析

主要观察了气孔在四季秋海棠营养器官和繁殖器官上的分布和发育情况,并分别对叶片和翅上气孔簇大小、气孔簇密度等指标的相关性进行了研究、结果表明:在叶片的下表皮、雌花和雄花的花被片、苞片、小苞片和翅上有气孔分布,而在茎、花梗上却未见气孔分布.叶片下表皮和翅上气孔通常成簇分布.在叶片的下表皮,气孔簇大小与气孔簇密度呈显著的负相关(P<0.05);气孔簇密度与叶片长度呈极显著的负相关(P<0.01).而翅上的气孔簇密度、气孔簇大小与子房长度无显著相关性(P>0.05).在四季秋海棠中,不同器官表皮的气孔簇大小是不同的,这可能与生理功能的不同有关.     

The Ultrastructure of the Glandular Trichomes of Solanum tuberosum

The potato plant has two types of glandular trichomes whichwere investigated by electron microscopy. One type has a eight celled globular head on a neck cell anda stalk cell Each glandular cell has many rather large vacuoles,a large nucleus, many ribosomes and mitochondria, a few Golgibodies, and darkly coloured, often irregular plastids (chloroplasts).The plastids are mostly located near the axial cell wall borderinga large central intercellular space filled with secretion materialThe plastids are assumed to participate in the formation ofthe secretion material, which reacts positively to esterasetests. The outer wall is covered by a thin cuticle. The other type has a club-shaped multicellular head on a singlestalk cell. The cytoplasmic features in the cells are similarto those of the globular-headed trichome, except that they possesslarge central vacuoles and randomly distributed plastids. Centricendoplasmic reticulum has been observed in young cells. Intercellularspaces develop between the cells and into the outer wall, whichis thus split into two. Whereas the older glandular cells reactpositively to tests for esterase, the secretion material itselfis pectinaceous and reacts negatively. The outer wall is cutinizedand covered by a cuticle. Solanum tuberosum L., potato, glandular trichomes, ultrastructure     

Carbon Transfer and Partitioning between Vegetative and Reproductive Organs in Pisum sativum L

Assimilate partitioning was studied in the common pea (Pisum sativum L.) by feeding ¹⁴CO₂ to whole plants and measuring radioactivity in different organs 48 hours after labeling. Two experimental protocols were used. For the first, one reproductive node was darkened with an aluminum foil, to prevent photosynthesis during labeling. The aim was to study assimilate translocation among nodes. The second was carried out to assess any priority among sinks. Whole plants were shaded, during labeling, to reduce carbon assimilation. Various developmental stages between the onset of flowering and the final stage in seed abortion of the last pod were chosen for labeling. When all photosynthetic structures at the first reproductive node were darkened at any stage of development after the formation of the first flower, the first pod was supplied with assimilates from other nodes. In contrast, later developed pods, when photosynthetic structures at their node were darkened, received assimilates from other nodes only when they were beyond their final stage in seed abortion. Reducing illumination to 30% did not change distribution of assimilated carbon between vegetative and reproductive structures, nor among pods. It appears that the relative proportion of ¹⁴C allocated to any one pod, compared to other pods, depends on the dry weight of that pod as a proportion of the total reproductive dry weight. When the plant was growing actively, following the start of the reproductive phase until a few days before the end of flowering, the top of the plant (i.e., all the organs above the last opened flower) had a higher sink strength and a higher relative specific activity than pods, suggesting that it was a more competitive sink for assimilates. The pattern of assimilate distribution described here provides an explanation for pod and seed abortion.     

Epidermal Structure and Ontogeny of Stomata in Vegetative and Reproductive Organs of Ephedra and Gnetum

The epidermal structure and development of stomata in vegetativeand reproductive organs of Ephedra foliata and Gnetum ula isdescribed. The epidermal cells are polygonal, isodiametric,or elongated with thick or thin straight, arched, or slightlysinuous anticlinal walls. The cuticle is thin or thick. Papilla-likeunicellular outgrowths are present in Ephedra foliata. The maturestomata are orientated parallel to the longitudinal axes orirregularly. The mature stomata are anomocytic, paracytic, witha single subsidiary cell, cyclocytic, and actinocytic. Arresteddevelopment, contiguous stomata, and stomata with aborted guardcells have been observed. The ontogeny of stomata on differentorgans of these two plants is typically haplocheilic or perigenousbut the stomatal apparatus varies from organ to organ.     

Water Loss via the Glandular Trichomes of Chickpea (Cicer arietinum L.)

During late vegetative growth chickpea leaves and stems canbe covered with aqueous glandular droplets. If these dropletspersist at low humidities there may be substantial water lossvia the glandular trichomes Four solution culture experimentsin growth chambers tested for glandular water loss at differenthumidities. In the daytime, exudate persisted between relativehumidities of 55% and 95%, and the exudate water potential variedbetween - 2.0 M Pa and - 8.0 M Pa. Even by night, chickpea leaves,like wetted alfalfa leaves, were cooler than non-wetted alfalfaleaves or the ambient air. Daytime leaf temperatures were significantlyhigher in a mutant that produced fewer droplets than in itsnormal parent. It was concluded that water loss via the glandulartrichomes can be enough to lower leaf temperature by severaldegrees C within a wide range of atmospheric conditions. The exudate solutes, analysed to confirm the osmotic potentialmeasurements, were primarily malic, hydrochloric and oxalicacid. Without the strong acids a chickpea leaf, wet even ondry days, would be ripe for parasitic attack. Key words: Add exudate, leaf hairs, transpiration, leaf temperature     

Glandular Trichomes on Alfalfa Impede Searching Behavior of the Potato Leafhopper Parasitoid

New cultivars of alfalfa, Medicago sativa L., have been released with glandular trichomes for resistance to potato leafhopper, Empoasca fabae (Harris). Yet, the impact of the glandular trichomes on the primary natural enemy of the leafhopper, Anagrus nigriventris Girault, is unknown. We compared the host searching behavior of the egg parasitoid on four alfalfa clones varying in trichome characters. Female wasps were videotaped on Ranger, a susceptible clone with relatively sparse trichomes, B14, a resistant clone with dense but nonglandular trichomes, and FG12 and FG18, two resistant clones with glandular trichomes. Although the number of leafhopper eggs per stem exposed to wasps did not significantly differ among the four clones, the frequency of foraging and total foraging time were less on the two clones with glandular trichomes than on the two clones with nonglandular trichomes. In addition, an analysis of covariance demonstrated that, although the number of ovipositional probes increased with egg density on a stem, the number of probes on stems with glandular trichomes was significantly less than that on stems without glandular trichomes. The allocation of time by wasps among drumming, probing, and grooming behaviors was similar among the clones. Wasps tended to fly off of clones with glandular trichomes more often than off of clones with nonglandular trichomes. This study suggests that cultivars with glandular trichomes may interfere with host searching by A. nigriventris.     

Purification and Characterization of Polyphenol Oxidase from Glandular Trichomes of Solanum berthaultii

Type A glandular trichomes of the wild potato (Solanum berthaultii Hawkes) entrap insects by rapidly polymerizing the trichome contents after breakage by insect contact. Polymerization of trichome exudate appears to be driven by a soluble polyphenol oxidase (PPO). PPO constitutes up to 70% of the protein in individually collected trichomes and reaches a concentration approaching 200 μm in these organs. Trichome PPO has been purified and shown to be a monomeric copper metalloprotein with an isoelectric point of 5.5, possessing only o-diphenol oxygen oxido-reductase activity, and is larger than most other reported PPOs, with relative molecular weight of 59,000. Chlorogenic and caffeic acid were the most readily oxidized of 14 phenolic substrates tested. Polyclonal antibodies raised against the relative molecular weight 59,000 S. berthaultii trichome PPO were used to show that S. tuberosum L. trichomes express low levels of a cross-reactive protein that lacks detectable PPO activity.     

Bidirectional Secretions from Glandular Trichomes of Pyrethrum Enable Immunization of Seedlings

Glandular trichomes are currently known only to store mono- and sesquiterpene compounds in the subcuticular cavity just above the apical cells of trichomes or emit them into the headspace. We demonstrate that basipetal secretions can also occur, by addressing the organization of the biosynthesis and storage of pyrethrins in pyrethrum (Tanacetum cinerariifolium) flowers. Pyrethrum produces a diverse array of pyrethrins and sesquiterpene lactones for plant defense. The highest concentrations accumulate in the flower achenes, which are densely covered by glandular trichomes. The trichomes of mature achenes contain sesquiterpene lactones and other secondary metabolites, but no pyrethrins. However, during achene maturation, the key pyrethrin biosynthetic pathway enzyme chrysanthemyl diphosphate synthase is expressed only in glandular trichomes. We show evidence that chrysanthemic acid is translocated from trichomes to pericarp, where it is esterified into pyrethrins that accumulate in intercellular spaces. During seed maturation, pyrethrins are then absorbed by the embryo, and during seed germination, the embryo-stored pyrethrins are recruited by seedling tissues, which, for lack of trichomes, cannot produce pyrethrins themselves. The findings demonstrate that plant glandular trichomes can selectively secrete in a basipetal direction monoterpenoids, which can reach distant tissues, participate in chemical conversions, and immunize seedlings against insects and fungi.     

Glandular Trichomes on the Leaves and Flowers of Plectranthus ornatus: Morphology, Distribution and Histochemistry

The types of glandular trichomes and their distribution on leavesand flowers of Plectranthus ornatus were investigated at differentstages of their development. Five morphological types of glandulartrichomes are described. Peltate trichomes, confined to theleaf abaxial surface, have, in vivo, an uncommon but characteristicorange to brownish colour. Capitate trichomes, uniformly distributedon both leaf surfaces, are divided into two types accordingto their structure and secretory processes. In long-stalkedcapitate trichomes, a heterogeneous secretion (a gumresin) isstored temporarily in a large subcuticular space, being releasedby cuticle rupture, whereas, in the short-stalked capitate trichomes,the secretion, mainly polysaccharidic, is probably exuded viamicropores. On the leaves, digitiform trichomes, which do notshow a clear distinction between the apical glandular cell andthe subsidiary cells, occur with a similar distribution to thecapitate trichomes. They do not develop a subcuticular space,and secrete small amounts of essential oils in association withpolysaccharides. The reproductive organs, particularly the calyxand corolla, exhibit, in addition to the reported trichomes,unusual conoidal trichomes with long unicellular conical heads.A large apical pore, formed by tip disruption, releases thesecretion (a gumresin) stored in a rostrum-like projection.On the stamens and carpels, digitiform, capitate and conoidaltrichomes are absent, but peltate trichomes are numerous. Theyoccur between the two anther lobes, on the basal portion ofthe style, and between the four lobes of the ovary. The resultspresented are compared with those of other studies on Lamiaceaeglandular trichomes. Copyright 1999 Annals of Botany Company Plectranthus ornatus Codd, Lamiaceae, glandular trichomes, morphology, histochemistry, essential oils and mucilage secretion.     

Development and Structure of Internal Glands and External Glandular Trichomes in Pogostemon cablin

Pogostemon cablin possesses two morphologically and ontogenetically different types of glandular trichomes, one type of bristle hair on the surfaces of leaves and stems and one type of internal gland inside the leaves and stems. The internal gland originates from elementary meristem and is associated with the biosynthesis of oils present inside the leaves and stems. However, there is little information on mechanism for the oil biosynthesis and secretion inside the leaves and stems. In this study, we identified three kinds of glandular trichome types and two kinds of internal gland in the Pogostemon cablin. The oil secretions from internal glands of stems and leaves contained lipids, flavones and terpenes. Our results indicated that endoplasmic reticulum and plastids and vacuoles are likely involved in the biosynthesis of oils in the internal glands and the synthesized oils are transported from endoplasmic reticulum to the cell wall via connecting endoplasmic reticulum membranes to the plasma membrane. And the comparative analysis of the development, distribution, histochemistry and ultrastructures of the internal and external glands in Pogostemon cablin leads us to propose that the internal gland may be a novel secretory structure which is different from external glands.     

The Development of Stomata in Vegetative and Reproductive Organs ofBupleurum tenue Buch.-Ham. ex D. Don

InBupleurum tenue stomata have been observed on leaf, stem,stalk of compound umbel and umbellet, bract of involucre andinvolucel, pedicel of flower, both surfaces of petal, outerepidermis of pericarp, and the stylopodium. Their developmentis of the syndetocheilic type in vegetative as well as the reproductiveorgans. In the stylopodium the stomata are anomocytic whilein the rest of the organs they are anisocytic.     

Preformation of Node Number in Vegetative and Reproductive Proleptic Shoot Modules of Persea (Lauraceae)

The numbers of nodes on single flush terminal and axillary shootmodules were determined in a range of Persea species and cultivars.They were compared with node numbers in apical and axillarybuds to investigate whether preformation or neoformation ofnodes occurred. Mean number of nodes on terminal shoots was14 for vegetative shoot modules and 21 for reproductive shootmodules, and was similar across species, cultivars, rootstocks,locations and climates. In the cultivar 'Hass', numbers of nodeson axillary shoot modules were variable, and lower than thosefor primary shoot modules forming the dominant growth axis ofannual growth modules. There was a mean of 12 nodes for vegetativeproleptic shoot modules, 15 for reproductive proleptic shootmodules and six for sylleptic shoot modules, which were invariablyvegetative. All nodes were preformed within both apical andaxillary proleptic buds. This was not the case in syllepticbuds, which burst contemporaneously with extension of the parentaxis. The majority (63%) of reproductive buds formed indeterminatecompound inflorescences. They carried six basal bud scales,six axillary inflorescences and their subtending bracts, andup to nine true leaves.Copyright 1994, 1999 Academic Press Persea Clus., avocado, Persea americana Mill., bud morphology, shoot growth, preformation, prolepsis