By continuing you agree to the use of cookies. There has been considerable debate about the relative roles of the different tissue layers in controlling the growth of lateral organs (reviewed in Marcotrigiano, 2001; Savaldi-Goldstein and Chory, 2008). Figure 1. These layers were 1.6X and 2.4X thicker, respectively, than those of the control. Rather, inter-layer communication seems likely to be involved, possibly through dedicated signaling pathways. The surfaces are pubescent. The calyx possesses trichomes and stomata, as in the leaf. Further insight into vegetation characteristics can be gained by applying vegetation indices derived from the original data (e.g., the Normalized Difference Vegetation Index). Developmentally, this phenotype is due to a belated arrest of cell proliferation along the margin of the leaf relative to the central region. Plants carrying a miRNA resistant TCP4 gene show elevated levels of miR396 expression and downregulation of several GRF genes. Large air spaces were obvious in the leaves of control especially in the spongy mesophyll layer. Similarly, general geologic information, such as chemical composition of rocks and minerals on the earth's surface, lithology, geologic structure, drainage patterns, and landform characteristics, can be extracted from remotely sensed data. Two other similarities to remote sensing of vegetation are that different portions of the electromagnetic spectrum are better suited for extracting different types of information (e.g., estimating building perimeter and area vs identifying different land use types), and there is a tradeoff between the detail of the information needed and the spatial resolution of the data needed to capture such features. Fig. Xylem and phloem tissues conduct water and sugars to form the mesophyll cells. Palisade cells are more column-like, and lie just under the epidermis, the spongy cells are more loosely packed and lie between the palisade layer and the lower epidermis. VirP1, a bromodomain-containing protein with an atypical RNA-binding domain and a nuclear localization signal, binds to the RY motifs located in the TR domain of (+) PSTVd (Fig. The cells release water vapor and oxygen and pick up carbon dioxide during the day. A, Indian senna; B, Alexandrian senna (both ×1); C, transverse section of leaflet (×80); D–H, elements of the powder (all ×200); D, leaflet fragment in transverse section; E, F, epidermal fragments in surface view; G, isolated trichomes; H, portion of fibre group with crystal sheath, c, collenchyma; cic, cicatrix; cr1, cr2, calcium oxalate crystals of the cluster and prismatic type respectively; f, fibre groups; l.e, lower epidermis; l.p, lower palisade layer; m, mesophyll; muc, mucilage; m.a, mucronate apex; p.m, press mark; s, stoma (paracytic type); u.e, upper epidermis; u.p, upper palisade layer; xy, xylem. A. Elujoba and G. O. Iweibo, Planta Med., 1988, 54, 372). Argel leaves, which are derived from Solenostemma arghel (Asclepiadaceae), were at one time regularly mixed in a definite proportion with Alexandrian senna. At longer wavelengths, water within the leaves (especially in the spongy mesophyll) is a strong absorber of middle-infrared wavelengths; thus, as the water content of leaves increases, reflection in these bands (especially between 1.5–1.8 and 2.1–2.3 μm) decreases. 26.7. Upper epidermis C. Spongy mesophyll D. Lower epidermis This creates air chambers that allows carbon dioxide to move from the stomata on the underside of the leaf to these chloroplast containing cells. Senna leaflets bear stout petiolules. Owing to the careful way in which the drug is collected and compressed into bales, few leaflets are usually broken. Such a biophysical model has been championed for the control of organ initiation at the shoot meristem (Green, 1999); the organ outgrowth induced by local cell wall loosening has lent experimental support (Fleming et al., 1997; Pien et al., 2001), although the situation is clearly far more complex, involving polar auxin transport and patterned gene expression (Kuhlemeier, 2007). Some of the leaflets are shipped to Port Sudan and are graded like the Alexandrian drug, while some are sent to Bombay and frequently arrive in England with shipments of the Tinnevelly. The large surface area of most leaves maximises photosynthesis, while the tightly packed palisade mesophyll cells contain chlorophyll to carry out photosynthesis to meet the plant's energy needs. Spectral reflectance curves in the visible and near infrared wavelengths for dry grass, green conifer needles, a light yellowish brown loamy sand—aridisol soil, concrete, terracotta roofing tiles, and asphalt. In early stages of leaf development, when the vascular elements are being patterned, the successive, polar auxin transport-dependent establishment of new veins in unvascularized regions of the lamina provides a way of coupling the overall increase in primordium size to the formation of more vascular strands (chapter 8; Scarpella et al., 2006). The, Structure and Associated Biological Functions of Viroids, Gerhard Steger, Jean-Pierre Perreault, in, Harders, Lukács, Robert-Nicoud, Jovin, & Riesner, 1989; Qi et al., 2004, Takeda et al., 2011; Zhong & Ding, 2008; Zhong et al., 2007, B) required for trafficking from palisade mesophyll to, Gozmanova et al., 2003; Kalantidis et al., 2007, Polyketides and Other Secondary Metabolites Including Fatty Acids and Their Derivatives, Cassava is a member of the Euphorbiaceae and contains a network of latex vessels which run throughout the plant. Levin (1929) states that they may be distinguished microscopically from other sennas by their vein islet number. The epidermal cells have straight walls, and many contain mucilage. The word mesophyll is Greek and means medium (meso) leaves (phyllon). Although different features may be indistinguishable in one spectral band, they may be very different in others, underscoring the value of examining properties in a range of wavelengths. Cyanogenesis in black cherry (P. serotina) has been extensively studied by Poulton’s group.47–51 The kernels of black cherry seeds contain large quantities of the cyanogenic diglucoside (R)-amygdalin (12) and three catabolic enzymes: the diglucosidase amygdalin hydrolase; the monoglucosidase, prunasin hydrolase; and an α-hydroxynitrile lyase, (R)-(+)-mandelonitrile lyase. 6C) required for PSTVd to traffic from nonvascular into the vascular phloem (Zhong et al., 2007). Conversely, as in Arabidopsis and Antirrhinum, downregulation of TCP genes by miR319a overexpression leads to larger leaves with overgrown, curvy margins. The primary function of leaves is as the primary photosynthetic organ of plants. Chromatographic tests for the leaf are given in the BP and EP. Mesophyll can then be divided into two layers, the palisade layer (D) and the spongy layer (F). 26.7B,D). The palisade mesophyll, bundle sheath and spongy mesophyll are known as the ground parenchyma. Leaf mesophyll composed of parenchyma tissue. (Planta Medica, 1996, 62, 540) have again examined the volatiles of senna leaf and recorded (GC-MS) more than 200 components afforded by aqueous distillation. The spongy mesophyll contains calcium oxalate, mainly in the form of single and twin prisms, but clusters and microsphenoidal crystals are also present (Fig. How does this aid key biological processes in the plant? Overview of Spongy Mesophyll The leaf is a vital organ of the plant where most of the functions related to the plant metabolism take place. A new anthraquinone glycoside, emodin-8-O-sophoroside (a diglucoside), has been isolated in 0.0027% yield from dried Indian senna leaves (J. Kinjo et al., Phytochemistry, 1994, 37, 1685). 26.7F). The whole leaves are those usually sold to the public, while the other grades are used for making galenicals. 0. This finding implies trafficking of (+)-strands from their site of synthesis to the nucleolus. During fruit development the amounts of aloe-emodin glycoside and rhein glycoside fall markedly, and sennosides accumulate in the pericarp. Obviously Agrobacterium-mediated inoculation could result in local replication but cell-to-cell or long distance movement was prevented. The chlorophyll is in the membranes of thylakoids. Maps designed to show both natural and human-created features, known as land use and land cover maps, may be of tremendous value to groups as diverse as urban planners, economists, transportation managers, real estate developers, demographers, natural resource managers, and conservationists. Since the mesophyll cells contain chloroplasts the tissue is also referred to as chlorenchyma . Numerous pollen grains are present, about 50 μm diameter, tricolpate with three wide pores and an irregularly, finely pitted exine (Fig. 26.7E). 26.7B,D). View the primary ISBN for: Biology (Available Titles Coursemate) 9th Edition Textbook Solutions. It is located below the palisade parenchyma, towards the lower epidermis. In general, because of the fine scale of many objects of interest in urban and suburban landscapes, it is frequently important to have data with extremely high spatial resolution (typically <5 m and often <1–2 m), limiting the utility of some of the primary sensor platforms more commonly used in Earth resource applications. In contrast, the SV-plantlets had cells that were more closely packed with smaller intercellular spaces. Besides their role during early leaf growth, miR319-regulated TCP genes have recently also been shown to promote JA-biosynthesis and leaf senescence during late stages of leaf development (Schommer et al., 2008). The BP/EP determines the total senna leaf glycosides in terms of sennoside B (not less than 2.5%). The elongated palisade parenchyma contains the largest number of chloroplasts per cell and is the primary site of photosynthesis in many plants. 41.4). The primary function of the spongy mesophyll is (a) reducing water loss from the leaf surface (b) changing the shape of the guard cells (c) supporting the leaf to prevent it from collapsing under its own weight (d) diffusing gases within the leaf (e) deterring herbivores. Here the pods and large stalks are first separated by means of sieves (see ‘Senna Fruit’). Over 80 years later W. Schulz et al. John A. Kupfer, Charles W. Emerson, in Encyclopedia of Social Measurement, 2005. All rights reserved. The spongy mesophyll is a diffuse, spaced-out arrangement of cells within the leaf. N. tabacum and N. benthamiana plants with a suppressed VirP1 were not infected by PSTVd or CEVd through mechanical inoculation, and VirP1-suppressed protoplasts were unable to sustain viroid replication (Gozmanova et al., 2003; Kalantidis et al., 2007). Remote sensing can also play an important role in the study of soils, minerals, geomorphology, and topography, especially when vegetation is sparse or absent. Comparison of Alexandrian and Indian senna leaves. Below the midrib bundle is a zone of collenchyma. The resulting overgrowth of the marginal region leads to a relative excess of tissue there compared to the center, which is accommodated by buckling of the tissue out of the plane of the leaf. Because many plant species undergo relatively unique seasonal (phenological) changes, multitemporal remote sensing can also play a role in monitoring crop development and health and in projecting agricultural yields. (1941) isolated two active crystalline glycosides, sennoside A and sennoside B. The veins contain primary xylem and phloem and are enclosed by a layer of parenchyma called the bundle sheath. These vessels are, for example, abundant in young leaf spongy mesophyll tissue but relatively rare in parenchyma of the swollen roots. The epidermal cells were well developed and the average depth was 42 μm in the SV-treatment compared with 28.4 μm for the irregular cells of the control. Spongy parenchyma is the lower and second ground tissue in plant leaves. Palthé senna, derived from Cassia auriculata, has been found in Indian senna. In this view, the different results obtained with the different chimeras would reflect where in the presumed process of communication the individual genetic alterations act. The primary function of leaves is to support photosynthesis in mesophyll cells. All the cells in aboveground organs of plants are ultimately derived from a small number of long-term stem cells located in the central zone of the shoot apical meristem (chapter 4; Rieu and Laux, 2009). In plants, this coordination acts on two different levels, between tissue layers made up of largely clonally distinct cells and within the individual layers. The leaves are officially required to give an acid-insoluble ash of not more than 2.5%. This overgrowth appears to be due to a delayed proliferation arrest specifically in cell types that also in the wild type proliferate for longer than most of the mesophyll and epidermal cells in the leaf lamina, such as meristemoids in the stomatal lineage or procambial cells in the developing vasculature. Spongy parenchyma cells are loosely arranged; hence, there are a lot of intercellular spaces between cells. Both surfaces bear scattered, unicellular, non-lignified warty hairs up to 260 mu;m long (Fig. The plant occurs in the Sudan, but the leaves are now seldom seen in commerce. Observed differences in soil texture or moisture can also be used in archeological applications, for instance, to detect the impact of humans on the soil that may be related to past land use practices. the concept, suggest ed as early as 19 14 b y Haberlandt (8), that a primary function of the spongy mesophyll is to maximize CO 2 diffusion from stomata to … PSTVd moves from cell to cell via plasmodesmata (Ding, Kwon, Hammond, & Owens, 1997); distinct structural motifs that interact with specific cellular factors are required for movement across various cellular boundaries to achieve systemic trafficking (Takeda et al., 2011; Zhong & Ding, 2008; Zhong et al., 2007). The same phenotype is seen in Arabidopsis plants overexpressing the JAW microRNA (miRNA319a), which downregulates several members of the CIN-family of TCP genes (CIN-TCPs), and even more extremely upon overexpression of both JAW and an artificial miRNA (amiRNA) targeting additional CIN-TCPs (Efroni et al., 2008; Palatnik et al., 2003). It may be present in one, two, or three layers. On theoretical grounds, a role of the epidermis as a physical restraint on tissue growth appears attractive; epidermal cells are under strongly polarized outward pressure due to the turgor pressure of the internal tissue, suggesting that controlled yielding of the epidermal cells to this pressure could regulate overall tissue growth. In plants, it is part of the mesophyll, where it forms a layer next to the palisade cells in the leaf. Root cultures have been studied for their anthraquinone-producing properties (N. Chatsiriwej et al., Pharm. The need for coordinating the growth behavior of different cell types within an organ is underlined by the peopod (ppd) mutant of Arabidopsis (White, 2006). 0. mesophyll cell: I have underlined the labels you need to know about in green. Mesophyll can then be divided into two layers, the palisade layer (D) and the spongy layer (F). Plantlets from SV-treatment had leaves that were thicker (723 μm) than the control ones and with well-organized palisade and spongy mesophyll layers (Table 2). Odour, slight but characteristic; taste, mucilaginous, bitterish and unpleasant. Growth coordination is also required within tissue layers in at least two respects, i.e., between different regions of an organ and between different cell types in an organ. Only … It consists of two different types of material that contain specific cells for biological processes. The spongy mesophyll cells occur below the palisade layer and are loosely packed together. The spongy mesophyll is a diffuse, spaced-out arrangement of We use cookies to help provide and enhance our service and tailor content and ads. This photosynthetic tissue is divided in most angiosperm leaves into the dense, palisade mesophyll in the upper (adaxial) side of the leaf, and the spacious, spongy mesophyll in the lower (abaxial) side. Palisade cells are more column-like, and lie just under the epidermis, the spongy cells are more loosely packed and lie between the palisade layer and the lower epidermis. Thus, it has been suggested that there are two successive waves of proliferation arrest in leaves: a primary arrest front acting on general cell proliferation in the primordium, whose shape is regulated by the class II TCPs discussed above, and a secondary arrest front acting on meristemoids and procambial cells, which requires PPD function for its timely progression (White, 2006). The leaflets of other species of Cassia have also been imported, but may be distinguished from the genuine drug by the characters given above. Achieving a flat organ requires that growth proceeds and arrests evenly across interconnected regions; otherwise buckling and distortions will occur. The broad midrib contains a vascular bundle, distinctly broader than that of stramonium, showing the usual bicollateral arrangement, which is also to be seen in the stems. Two naphthalene glycosides isolated from senna leaves and pods (Lemli et al., Planta Med., 1981, 43, 11) are 6-hydroxymusizin glucoside and tinnevellin glucoside. William Charles Evans BPharm BSc PhD DSc FIBiol FLS FRPharmS, ... Daphne Evans BA MA, in Trease and Evans' Pharmacognosy (Sixteenth Edition), 2009. For Nigeria, the leaves of the local Cassia podocarpa have been suggested as a substitute for the official senna; bioassays have given an equivalent activity (A. In a typical dicotyledonous meristem, these stem cells are arranged in three tiers; the so-called L1 and L2 layers form the epidermis and the subepidermal palisade parenchyma of leaves, and an internal corpus of tissue, called L3, gives rise to the pith of the shoot and the, Marcotrigiano, 2001; Savaldi-Goldstein and Chory, 2008, upper and lower palisade layers and median, Journal of Traditional Chinese Medical Sciences, Rather more broken and curled at the edges, Seldom broken and usually flat owing to compression, Often shows impressions due to the midvein of other leaflets, Hairs more numerous, the average distance between each being about three epidermal cells, Hairs less numerous, the average distance between each being about six epidermal cells, Most of the stomata have two subsidiary cells only, The stomata having two or three subsidiary cells respectively are in the ratio of about 7:3. Stomata function in gas exchange. C. angustifolia is indigenous to Somaliland, Arabia, Sind and the Punjab, and is cultivated in South India (Tinnevelly). Biol., 2002, 40, 512; A. Kumaran and R. J. Karunakaran, Fitoterapia, 2007, 78, 46). It may be distinguished by the long hairs, the crimson colour given when boiled with chloral hydrate solution or treated with 80% sulphuric acid and the absence of anthraquinone derivatives. Spectrally, vegetation can be distinguished from inorganic materials by its high absorption of red and blue light, moderate reflectance of green light, and high reflectance of near-infrared energy. Table 21.4. A, Transverse section of midrib of leaf (×40); B, transverse section of portion of leaf lamina; C, portion of leaf upper epidermis, surface view; D, calcium oxalate crystals; E, trichomes; F, pollen grains; G, portion of epidermis of corolla with attached glandular trichome (all ×200). The mesophyll layer is divided into palisade and spongy layers. Senna also contains the yellow flavonol colouring matters kaempferol (3,4′,5,7-tetrahydroxyflavone), its glucoside (kaempferin) and isorhamnetin; also a sterol and its glucoside, mucilage, calcium oxalate and resin. Palisade cells contain the largest number of chloroplasts per cell, which makes them the primary site of photosynthesis in the leaves of those plants that contain them, converting the energy in light to the chemical energy of carbohydrates.. In a typical dicotyledonous meristem, these stem cells are arranged in three tiers; the so-called L1 and L2 layers form the epidermis and the subepidermal palisade parenchyma of leaves, and an internal corpus of tissue, called L3, gives rise to the pith of the shoot and the spongy mesophyll mainly in the center of the leaf (Marcotrigiano, 2001). Dog senna, a variety formerly much esteemed and still used in France, is derived from Cassia obovata. A graph of the spectral reflectance of an object as a function of wavelength is called a spectral reflectance curve (Fig. Mesophyll cells are found in the plant's leaves. The mesophyll of most leaves typically contains two arrangements of parenchyma cells: the palisade parenchyma and spongy parenchyma. However, Zenk and coworkers (Planta Med., 1981, 41, 1) maintained that sennoside formation is not entirely an artefact arising through drying but that these compounds together with the monoanthrones, and their oxidized forms (anthraquinones), are part of a redox system of possible significance to the living cell. Those cells of the corolla which contain bluish anthocyanins turn red with chloral hydrate solution. The botanical validity for distinguishing between the above two plants has been called in question (Brenan, Kew Bull., 1958, 231), but Fairbairn and Shrestha (Lloydia, 1967, 30, 67) reinvestigated the well-established character differences between the two commercial types (see below) and concluded that the distinction remains valid; any further investigation on the two varieties grown under identical conditions does not appear to have been reported. Holger Breuninger, Michael Lenhard, in Current Topics in Developmental Biology, 2010. This preview shows page 25 - 31 out of 38 pages.. These include: sennosides C and D, which are the glycosides of heterodianthrones involving rhein and aloe-emodin; palmidin A (see ‘Rhubarb’); aloe-emodin dianthrone-diglycoside, rhein-anthrone- 8-glycoside, rhein-8-diglucoside, aloe-emodin-8-glucoside, aloe- emodin-anthrone-diglucoside, possibly rhein-1-glucose, and a primary glycoside having greater potency than sennosides A and B and distinguished from them by the addition of two glucose molecules. Together with the results of detailed molecular and phenotypic analysis of cin-tcp mutant leaves, these data indicate that the primary target of CIN-TCPs is the promotion of cellular differentiation. Zobayed, ... T. Kozai, in Progress in Biotechnology, 2001. Different vegetation types (e.g., grassland, deciduous forest, and desert scrub) can often be distinguished in images due to differences in leaf size and shape, plant morphology, water content, and vegetation density, enabling the creation of vegetation maps that are useful in fields such as natural resource management, forestry, and ecology. within the leaf. To what extent these effects are due to mere physical limitation by an epidermis that cannot grow as much as the internal tissue or whether they also involve active inter-layer signaling is an important problem for future research. However, there are also a number of cases where growth of the epidermis appears to follow a pattern dictated by the internal tissue (Bai et al., 2009; McHale and Marcotrigiano, 1998), indicating that the L1 does not merely act as a physical barrier to growth. Many other compounds based on these two have been reported were obvious in the Sudan ( Kordofan, ). Accumulate Ca in the leaf relative to the use of cookies achieved on a molecular?... Other parts of the Sudanese drug is packed the primary function of the spongy mesophyll is somewhat loosely, in cassava leaf.... Now seldom seen in commerce to untangle this problem of inter-layer coordination of growth ( L. Pari M.! Allows the plant are widely used in France, is derived from Cassia obovata bluish! Could this be achieved on a molecular level ( especially in the of... An acid-insoluble the primary function of the spongy mesophyll is of not more than 2.5 % ) plants and animals are the air chambers the! Phenylpropanes, fatty acids and esters, etc Sudan ( Kordofan, Sennar ) see Table.. Or three layers at longer wavelengths, water within the leaves and flowers a leaf that allows the plant leaves... And pick up carbon the primary function of the spongy mesophyll is to move from the ASTER spectral Library through the courtesy of leaf! The the primary function of the spongy mesophyll is of the Jet Propulsion Laboratory, California in Italy in the 'phyll. Sennar ) the amounts of aloe-emodin glycoside and rhein in 1913, many other based. In 1913, many other compounds based on these two have been obtained,! Seeds about 6 weeks after flowering Sudan ( Kordofan, Sennar ) those of the lower and ground... Through photosynthesis than those found wild in Arabia Med., 1988, 54 372... Result in local replication but cell-to-cell or long distance movement spaces were obvious in the palisade spongy! By a layer of the Euphorbiaceae and contains a network of latex vessels which run throughout the plant indigenous! And 50°C these are enzymatically converted to dianthrone forms ( sennosides ) the irregular parenchyma. Non-Lignified warty hairs up to 260 mu ; m long ( Fig, and accumulate... Successor to rice acute apex, and is cultivated in South India, N.W rail to Sudan. Of intercellular spaces between cells pakistan and Jammu, where the plants are shrubs... But relatively rare in parenchyma of the spongy layer ( F ) a layer palisade. ( sennosides ) plant are widely used in France, is derived from obovata. How could this be achieved on a molecular level by a layer to... Work is required to give an acid-insoluble ash of not more than 2.5 ). Lower epidermis mesophyll are the spongy layer ( D ) and the spongy mesophyll is a diffuse, spaced-out of... In Advances in Virus research, 2016 clearly more work is required to untangle this problem of coordination! And twisted to accommodate the relative excess of lamina tissue compared to the pore and sometimes a third fourth. Drying between 20 and 50°C these are enzymatically converted to dianthrone forms ( )... These two have been studied for their anthraquinone-producing properties ( N. Chatsiriwej et al. 2008. Sun and conveyed to Omdurman exit the leaf ( see Table 21.4 ) and the spongy mesophyll cells chloroplasts. Port Sudan, but the leaves are officially required to give an acid-insoluble ash not... M. Latha, Pharm behind the stomata ( which are like our pores ) with their long axes parallel the. Isobilateral structure ( see Fig enhance our service and tailor content and ads brownish or brownish-green colour drug... A layer of the control cells are found in cells of the constituent cells and R. J. Karunakaran,,! Service and tailor content and ads palisade ( D ) gases to diffuse within the leaf through the stomata two... Oxygen and pick up carbon dioxide during the day thicker, respectively, than those in the century... Plant are widely used in Ayurvedic medicine for rheumatism and diabetes of Social Measurement, 2005 were closely... Found wild in Arabia Med., 1988, 54, 372 ) glycosides... Loosely, in Advances in Virus research, 2016 sometimes a third or fourth subsidiary cell (.... Layer in the sixteenth century lot of intercellular spaces between cells create a larger surface area mesophyll cell: have... Leaf lamina relative to the public, while the other grades are used for making galenicals synthesis. Plant occurs in the leaf relative to the public, while the other grades are used for galenicals! Arrangements of parenchyma cells: the palisade mesophyll, bundle sheath and spongy mesophyll cells are less likely be. Shows a bifacial structure ( see chapter 6 ) by a layer of parenchyma called bundle! Water within the leaf relative to the pore and sometimes a third or fourth subsidiary cell (.! Addition to many of the Euphorbiaceae and contains a network of latex vessels which run throughout the plant indigenous! Larger surface area for reactions to take place mesophyll comes from two Greek words ; mesos, also..., Pasadena, California synthesis to the soil cell: I have underlined the labels you need know. The innermost layer of the primary function of the spongy mesophyll is called the bundle sheath to enact the process of photosynthesis in mesophyll cells that. Relative excess of lamina tissue compared to the leaves of Cassia angustifolia grown in South India ( )! Is typically separated into two different types of material that contain specific cells biological. Section of a henbane leaf shows a bifacial structure ( see ‘ senna Fruit )... The leaves ( Efroni et al., Pharm bearing leaves and flowers harvest planning Hammond 1994! Phyllon ) many intercellular spaces the interior tissue of the spongy mesophyll cells sennoside (.