Anatomy and photosynthetic parameters of roots and leaves of two shade-adapted orchids, Dichaea cogniauxiana Shltr. and Epidendrum secundum Jacq.

This study compares photosynthetic and structural features of Dichaea cogniauxiana and Epidendrum secundum leaves and roots. The diurnal titratable acidity fluctuations indicated crassulacean acid metabolism (CAM) in E. secundum leaves, associated with anatomical features like thick cuticle, large and vacuolated cells, and reduced stomata size and frequency. Roots of both species had chloroplasts in their cortical parenchyma. However, neither the roots nor D. cogniauxiana leaves did show tissue sap acidity fluctuations. This indicates C₃ metabolism in these organs. This lack of oscillation of organic acids in Epidendrum roots was at odds with a CAM-like ¹³C ratio, suggesting that in spite of active CO₂ fixation in roots during the day, the bulk of carbon is imported from the leaves. Roots of both species showed Fv/Fm, ΔF/Fm′, ETR values similar to reports from other non-foliar photosynthetic organs. Besides reducing root carbon cost, root photosynthesis may also be important by alleviating potential hypoxia, since water-saturated velamen severely impedes the gas exchange between radicular cortex.     

Geographical and seasonal patterns of epiphytic diatoms on a subtropical mangrove (Kandelia candel) in southern China

Geographical and seasonal patterns of epiphytic diatoms on a subtropical mangrove (Kandelia candel (L.) Druce) were examined at four sites in southern China. A total of one hundred and three epiphytic diatom species and varieties belonging to 40 genera were identified. Dominant species included Nitzschia fasciculata, Luticola mutica and Achnanthes javanica var. subcontricta. Further analysis using canonical correspondence analysis revealed three diatom associations which could be closely related to environmental variables such as salinity and nutrients resources of nitrogen and phosphate. Epiphytic diatom assemblages on roots would be a good indicator for the evaluation of water quality in mangroves.     

Some structural and functional aspects of the epiphytic component of four seagrass species (Cymodoceoideae) from Papua New Guinea

The epiphytic component of four monospecific seagrass beds from Papua New Guinea was studied structurally and functionally. The floristic composition and abundance of the epiphytes on leaves of four seagrass species (Cymodoceoideae) showed considerable variation, but on all four seagrass species, the same algae were among the five quantitatively most important epiphytes: encrusting coralline algae, Cyanophyta, Ceramium gracillimum (Harv.) Mazoyer, Polysiphonia savatierii Hariot and Audouinella spp. The temporal pattern of the epiphytic algae showed more or less the same features on the four seagrass species.Annual mean biomass of epiphytes and seagrass leaves ranged from 54 g ADW m^?2 in a community of Cymodocea rotundata Ehrenb. and Hempr. ex Aschers. to 169 g ADW m^?2 in a community of Syringodium isoetifolium (Aschers.) Dandy. The contribution of the epiphytic component to the total above-ground biomass ranged from 22 to 24%. Productivity of epiphytes was highest on leaves of Halodule uninervis (Forssk.) Aschers. (2.12 g ADW m^?2 sediment surface day^?1) and the epiphytic community contributed 35–44% of the total above-ground production of these four seagrass communities.     

Bacterial Communities Associated with the Leaves and the Roots of Arabidopsis thaliana

Diverse communities of bacteria inhabit plant leaves and roots and those bacteria play a crucial role for plant health and growth. Arabidopsis thaliana is an important model to study plant pathogen interactions, but little is known about its associated bacterial community under natural conditions. We used 454 pyrosequencing to characterize the bacterial communities associated with the roots and the leaves of wild A. thaliana collected at 4 sites; we further compared communities on the outside of the plants with communities in the endophytic compartments. We found that the most heavily sequenced bacteria in A. thaliana associated community are related to culturable species. Proteobacteria, Actinobacteria, and Bacteroidetes are the most abundant phyla in both leaf and root samples. At the genus level, sequences of Massilia and Flavobacterium are prevalent in both samples. Organ (leaf vs root) and habitat (epiphytes vs endophytes) structure the community. In the roots, richness is higher in the epiphytic communities compared to the endophytic compartment (P = 0.024), while the reverse is true for the leaves (P = 0.032). Interestingly, leaf and root endophytic compartments do not differ in richness, diversity and evenness, while they differ in community composition (P = 0.001). The results show that although the communities associated with leaves and roots share many bacterial species, the associated communities differ in structure.     

Quantitative and qualitative variability of epiphytic algae on one Apiaceae (<Emphasis Type="Italic">Apium nodiflorum</Emphasis> L.) in a karstic river (Southeast of France)

Spatial distribution of the firmly attached epiphytic algae was investigated directly on the leaves of one Apiaceae (Apium nodiflorum L.) commonly found in chalky Mediterranean rivers, at two sampling dates (summer and autumn). The composition and structure of the epiphytic communities of the samples were determined at different levels: along the leaves, on both their sides and within each leaflet (n = 13). Forty-eight leaflets from four randomly selected plants were cut along the longitudinal and vertical axes so as to define 16 microhabitats located on the edge, the centre and the vein. Only a few species of algae were found to be constantly present whatever the sampling date, and dominated all microzones (n = 768). Their presence seemed to depend, rather, on the architectural structure of the plant. The other algae represented the major part of the epiphytic community and were only occasionally present. Those were more subject to temporal and environmental variations and less specific of the substrate. The epiphytes showed considerable spatial heterogeneity within their microhabitats, with an evident preference for the centre and the edge of the leaves, whereas two inhospitable spaces were the vein and apex. On the other hand, when the study was performed at a larger scale (along the leaf), the epiphytic populations of the youngest leaves (near the surface) and the eldest ones (close to the sediments) were homogenous, hence suggesting that other factors, independent from the physiology of the plant, may have an impact on epiphytic distribution.     

How significant are endophytic fungi in bromeliad seeds and seedlings? Effects on germination,survival and performance of two epiphytic plant species

In bromeliads, nothing is known about the associations fungi form with seeds and seedling roots. We investigated whether fungal associations occur in the seeds and seedling roots of two epiphytic Aechmea species, and we explored whether substrate and fungal associations contribute to seed germination, and seedling survival and performance after the first month of growth. We found a total of 21 genera and 77 species of endophytic fungi in the seeds and seedlings for both Aechmea species by Illumina MiSeq sequencing. The fungal associations in seeds were found in the majority of corresponding seedlings, suggesting that fungi are transmitted vertically. Substrate quality modulated the germination and growth of seedlings, and beneficial endophytic fungi were not particularly crucial for germination but contributed positively to survival and growth. Overall, this study provides the first evidence of an endophytic fungal community in both the seeds and seedlings of two epiphytic bromeliads species that subsequently benefit plant growth.     

干旱胁迫对黄土高原4种蒿属植物叶形态解剖学特征的影响

以黄土高原演替初期阶段的猪毛蒿(Artemisia scoparia Waldst.et Kit.)、茭蒿(Artemisia giraldii Pamp.)、铁杆蒿(Artemisia gmelinii Web.ex Stechm.)3种优势种和1种常见种黄花蒿(Artemisia annua Linn.)为供试材料,采用盆栽试验与称重控水法,将土壤含水量分别控制在田间最大持水量的75%(适宜水分对照)、55%(中度干旱)和35%(重度干旱),研究干旱胁迫对菊科蒿属植物叶片形态解剖学的影响,揭示植物叶片生态适应机制,为生态恢复过程中植被演替的规律提供理论依据。于植物营养生长末期选取代表性的叶片,分别采用电子扫描显微镜、电子透射显微镜和光学显微镜对叶表皮特征、亚细胞显微特征和组织结构进行观察。结果表明:干旱胁迫下,这4种植物表现为不同程度的叶片增厚、栅栏组织厚度、叶片紧实度和角质层厚度增加;3种旱生型植物猪毛蒿、茭蒿和铁杆蒿的叶片下表皮具有浓密的表皮毛,有利于防止水分过度蒸腾,而中生型黄花蒿叶片无此功能;铁杆蒿和黄花蒿上表皮毛稀少,不利于保水和防止强光照,干旱胁迫下依靠降低上表皮气孔密度和叶细胞叶绿体数目来适应环境;茭蒿和猪毛蒿叶绿体形态相似,具有较厚的基粒和浓密的基粒片层,强光下容易引起氧化损伤,猪毛蒿通过浓密的上表皮毛而茭蒿通过较强的抗氧化机制防止光能过剩,两者在重度干旱下均产生大量脂质体。4种蒿属植物中黄花蒿的叶片解剖学特征受到干旱的影响变化最大,铁杆蒿和猪毛蒿次之,茭蒿最弱,3种优势种的干旱适应性显著强于黄花蒿,干旱下叶片解剖学的结论与干旱耐受性指标结果一致。     

Comparison of the Behavior of Epiphytic Fitness Mutants of Pseudomonas syringae under Controlled and Field Conditions

The epiphytic fitness of four Tn5 mutants of Pseudomonas syringae that exhibited reduced epiphytic fitness in the laboratory was evaluated under field conditions. The mutants differed more from the parental strain under field conditions than under laboratory conditions in their survival immediately following inoculation onto bean leaves and in the size of the epiphytic populations that they established, demonstrating that their fitness was reduced more under field conditions than in the laboratory. Under both conditions, the four mutants exhibited distinctive behaviors. One mutant exhibited particularly large population decreases and short half-lives following inoculation but grew epiphytically at near-wild-type rates, while the others exhibited reduced survival only in the warmest, driest conditions tested and grew epiphytically at reduced rates or, in the case of one mutant, not at all. The presence of the parental strain, B728a, did not influence the survival or growth of three of the mutants under field conditions; however, one mutant, an auxotroph, established larger populations in the presence of B728a than in its absence, possibly because of cross-feeding by B728a in planta. Experiments with B728a demonstrated that established epiphytic populations survived exposure of leaves to dry conditions better than newly inoculated cells did and that epiphytic survival was not dependent on the cell density in the inoculum. Three of the mutants behaved similarly to two nonpathogenic strains of P. syringae, suggesting that the mutants may be altered in traits that are missing or poorly expressed in naturally occurring nonpathogenic epiphytes.     

Structures and functions of adventitious roots in species of the genus Philodendron Schott (Araceae)

We discuss here the anatomical variations of the arrangements and compositions of stele types observed in different roots types in four populations of the three species of Philodendron as probable adaptations to their habitats. Terrestrial individuals of P. corcovadense have cylindrical steles while rupicolous individuals have lobate steles with dispersed internal cortical parenchyma. The Philodendron species sampled showed polyarch structures. The crampon roots of P. oblongum and anchor roots of P. cordatum show medullated protosteles, with the former species having a reduced pith with sclerified parenchyma cells while the latter has a wide pith and parenchyma cells with only slightly thickened walls. The feeder roots of P. cordatum also show a medullated protostele—although a central vessel is present until approximately 60 cm from the apex that later disappears, forming a parenchymatous pith. We conclude that the different root types reflect adaptations of the subgenera Philodendron and Meconostigma to their different habits and habitats, such as in P. corcovadense, where the roots of rupicolous individuals have lobate steles while the roots of the terrestrial plants have cylindrical steles.     

Differences between Pseudomonas syringae pv. syringae B728a and Pantoea agglomerans BRT98 in Epiphytic and Endophytic Colonization of Leaves

The leaf colonization strategies of two bacterial strains were investigated. The foliar pathogen Pseudomonas syringae pv. syringae strain B728a and the nonpathogen Pantoea agglomerans strain BRT98 were marked with a green fluorescent protein, and surface (epiphytic) and subsurface (endophytic) sites of bean and maize leaves in the laboratory and the field were monitored to see if populations of these strains developed. The populations were monitored using both fluorescence microscopy and counts of culturable cells recovered from nonsterilized and surface-sterilized leaves. The P. agglomerans strain exclusively colonized epiphytic sites on the two plant species. Under favorable conditions, the P. agglomerans strain formed aggregates that often extended over multiple epidermal cells. The P. syringae pv. syringae strain established epiphytic and endophytic populations on asymptomatic leaves of the two plant species in the field, with most of the P. syringae pv. syringae B728a cells remaining in epiphytic sites of the maize leaves and an increasing number occupying endophytic sites of the bean leaves in the 15-day monitoring period. The epiphytic P. syringae pv. syringae B728a populations appeared to originate primarily from multiplication in surface sites rather than from the movement of cells from subsurface to surface sites. The endophytic P. syringae pv. syringae B728a populations appeared to originate primarily from inward movement through the stomata, with higher levels of multiplication occurring in bean than in maize. A rainstorm involving a high raindrop momentum was associated with rapid growth of the P. agglomerans strain on both plant species and with rapid growth of both the epiphytic and endophytic populations of the P. syringae pv. syringae strain on bean but not with growth of the P. syringae pv. syringae strain on maize. These results demonstrate that the two bacterial strains employed distinct colonization strategies and that the epiphytic and endophytic population dynamics of the pathogenic P. syringae pv. syringae strain were dependent on the plant species, whereas those of the nonpathogenic P. agglomerans strain were not.     

Effects of simulated acid rain on the foliar micromorphology and anatomy of tree tropical species

In order to correlate sintomatology with anatomical alterations caused by acid rain in leaves of tropical species, seedlings and saplings of Spondias dulcis Forst. F., Mimosa artemisiana Heringer and Paula and Gallesia integrifolia (Spreng.) Harms were exposed to simulated low-pH acid rain (pH 3.0). Control plants were submitted only to rain with distilled water (pH 6.0). The plants were exposed daily to the acid rain for 20 min for 10 consecutive days. Necrotic spots on the leaf blade occurred and most of the injuries onset on the epidermis in all species studied. S. dulcis displayed epicuticular wax erosion and rupture of epidermis. The abaxial surface of M. artemisiana was colonized by a mass of fungi hyphae and stomatal outer ledge rupture occurred. Some epidermal cells of G. integrifolia showed appearance similar to plasmolysis. The plants accumulated phenolic compounds in necrotic areas. Afterwards, leaves presented injuries in the mesophyll and collapsed completely. Cells surrounding the injured areas accumulated starch grains in S. dulcis. M. artemisiana showed more drastic symptom intensity in response to acidic rain. S. dulcis displayed visual symptoms similar to G. integrifolia, however, anatomical alterations were more severe.     

5种红树科植物叶片的比较解剖及其生态适应研究

用石蜡切片法对红树（Rhizophora apiculata Bl.）、红海榄（R.stylosa Griff.）、秋茄（Kandelia candel(Linn.) Druce）、木榄（Bruguiera gymnorrhiza(Linn.) Savigny）和海莲（B.sexangula(Lour.) Poir.）等5种红树科植物的叶片进行解剖学的观察和研究,结果表明：5种红树科植物叶片的表皮均有厚的角质膜和下皮层,表皮和下皮层的细胞常含有单宁;上表皮无气孔器;栅栏组织多层;木质部非常发达。说明了红树科植物的叶片具有很强的耐旱能力;同属植物的叶片在解剖结构上有着相似的特征。     

Significance of Na<Superscript>+</Superscript> and K<Superscript>+</Superscript> for Sustained Hydration of Organ Tissues in Ecologically Distinct Halophytes of the Family Chenopodiaceae

The contents of Na⁺, K⁺, water, and dry matter were measured in leaves and roots of euhalophytes Salicornia europaea L. and Climacoptera lanata (Pall.) Botsch featuring succulent and xeromorphic cell structures, respectively, as well as in saltbush Atriplex micrantha C.A. Mey, a halophyte having bladder-like salt glands on their leaves. All three species were able to accumulate Na⁺ in their tissues. The Na⁺ content in organs increased with elevation of NaCl concentration in the substrate, the concentrations of Na⁺ being higher in leaves than in roots. When these halophytes were grown on a NaCl-free substrate, a trend toward K⁺ accumulation was observed and was better pronounced in leaves than in roots. Particularly high K⁺ concentrations were accumulated in Salicornia leaves. There were no principal differences in the partitioning of Na⁺ and K⁺ between organs of three halophyte species representing different ecological groups. At all substrate concentrations of NaCl, the total content of Na⁺ and K⁺ in leaves was higher than in roots. This distribution pattern persisted in Atriplex possessing salt glands, as well as in euhalophytes Salicornia and Climacoptera. The physiological significance of such universal pattern of ion accumulation and distribution among organs in halophytes is related to the necessity of water absorption by roots, its transport to shoots, and maintenance of sufficient cell water content in all organs under high soil salinity.     

Spatial patterns of photosynthesis in thin- and thick-leaved epiphytic orchids: unravelling C3–CAM plasticity in an organ-compartmented way

Background and Aims

A positive correlation between tissue thickness and crassulacean acid metabolism (CAM) expression has been frequently suggested. Therefore, this study addressed the question of whether water availability modulates photosynthetic plasticity in different organs of two epiphytic orchids with distinct leaf thickness.

Methods

Tissue morphology and photosynthetic mode (C₃ and/or CAM) were examined in leaves, pseudobulbs and roots of a thick-leaved (Cattleya walkeriana) and a thin-leaved (Oncidium ‘Aloha’) epiphytic orchid. Morphological features were studied comparing the drought-induced physiological responses observed in each organ after 30 d of either drought or well-watered treatments.

Key Results

Cattleya walkeriana, which is considered a constitutive CAM orchid, displayed a clear drought-induced up-regulation of CAM in its thick leaves but not in its non-leaf organs (pseudobulbs and roots). The set of morphological traits of Cattleya leaves suggested the drought-inducible CAM up-regulation as a possible mechanism of increasing water-use efficiency and carbon economy. Conversely, although belonging to an orchid genus classically considered as performing C₃ photosynthesis, Oncidium ‘Aloha’ under drought seemed to express facultative CAM in its roots and pseudobulbs but not in its leaves, indicating that such photosynthetic responses might compensate for the lack of capacity to perform CAM in its thin leaves. Morphological features of Oncidium leaves also indicated lower efficiency in preventing water and CO₂ losses, while aerenchyma ducts connecting pseudobulbs and leaves suggested a compartmentalized mechanism of nighttime carboxylation via phosphoenolpyruvate carboxylase (PEPC) (pseudobulbs) and daytime carboxylation via Rubisco (leaves) in drought-exposed Oncidium plants.

Conclusions

Water availability modulated CAM expression in an organ-compartmented manner in both orchids studied. As distinct regions of the same orchid could perform different photosynthetic pathways and variable degrees of CAM expression depending on the water availability, more attention should be addressed to this in future studies concerning the abundance of CAM plants.     

Diverse non-mycorrhizal fungal endophytes inhabiting an epiphytic,medicinal orchid (<Emphasis Type="Italic">Dendrobium nobile</Emphasis>): estimation and characterization

Although the terrestrial and temperate orchids–fungal biology have been largely explored, knowledge of tropical epiphytic orchids–fungus relationships, especially on the ecological roles imparted by non-mycorrhizal fungal endophytes, is less known. Exploitation of the endophytic fungal mycobiota residing in epiphytic orchid plants may be of great importance to further elucidate the fungal ecology in this special habitat as well as developing new approaches for orchid conversations. The composition of fungal endophytes associated with leaves, stems and roots of an epiphytic orchid (Dendrobium nobile), a famous Chinese traditional medicinal plant, was investigated. Microscopic imaging, culture-dependant method and molecular phylogeny were used to estimate their entity and diversity. Totally, there were 172 isolates, at least 14 fungal genera and 33 different morphospecies recovered from 288 samples. Ascomycetes, coelomycetes and hyphomycetes were three major fungal groups. There were higher overall colonization and isolation rates of endophytic fungi from leaves than from other tissues. Guignardia mangiferae was the dominant fungal species within leaves; while the endophytic Xylariaceae were frequently observed in all plant tissues; Colletotrichum, Phomopsis and Fusarium were also frequently observed. Phylogenetic analysis based on ITS gene revealed the high diversity of Xylariacea fungi and relatively diverse of non-Xylariacea fungi. Some potentially promising beneficial fungi such as Clonostachys rosea and Trichoderma chlorosporum were found in roots. This is the first report concerning above-ground and below-ground endophytic fungi community of an epiphytic medicinal orchid, suggesting the ubiquitous distribution of non-mycorrhizal fungal endophytes in orchid plants together with heterogeneity and tissue specificity of the endophyte assemblage. Possible physiological functions played by these fungal endophytes and their potential applications are also discussed briefly. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

STRANGLER FIG ROOTING HABITS AND NUTRIENT RELATIONS IN THE LLANOS OF VENEZUELA

The strangler figs, Ficus pertusa and F. trigonata, are abundant in the seasonally flooded palm savanna (llanos intermedio) near Calabozo, Venezuela. The most common host tree for the hemiepiphytic figs is the palm Copernicia tectorum; nearly half of the palms support either an epiphytic or a ground-rooted fig. During their epiphytic stage the figs are rooted behind the palms' marcescent leaf bases. Material trapped behind the leaf bases is higher in organic matter, nitrogen, magnesium, and potassium than soil from the ground near the palms. The suggestion that nutrient availability to epiphytes is high is supported by the observation that concentrations of several nutrients, including N, P, and K, are significantly higher in epiphytic leaves than in tree leaves. Figs retain access to the epiphytic medium by producing upwardly growing (apogeotropic) roots that remain attached in the host palm's crown long after the fig has become firmly rooted in the ground. Although upward growing roots are expected to be more important in nutrient than water uptake, there are no obvious differences in the xylem anatomy of upward and downward growing fig roots. Terrestrial roots of fig trees are generally infected with vesicular-arbuscular mycorrhizae, but the epiphytic roots of the same individuals are not infected.     

Occurrence and distribution of tracheoidal elements in the Orchidaceae

Eighty-eight species of West African orchids were examined for tratheoidal elements in the root, stem, pseudobulb and leaf. Forty-three species (49%) contained tiacheoidal elements. al were epiphytic species; none of the twelve terrestrial and one epilithic/terrestrial species examined contained tracheoidal elements. Of the epiphytic species, twenty-one contained tracheoidal elements in the roots; seventeen in the stem/pseudobulb and twenty-three in the leaves.
The tracheoidal elements are similar in structure: they all possess annular, spiral, reticulate or pitted secondary wall thickenings. These elements vary in shape, size and distribution in the different species and these variations may be of some taxonomic use within the Orchidaceae.
The functions of the tracheoidal elements is not clear, but they probably provide mechanical support and also aid water -retention in the organs containing them.     

Water relations of epiphytic and terrestrially-rooted strangler figs in a Venezuelan palm savanna

Water use patterns of two species of strangler fig, Ficus pertusa and F. trigonata, growing in a Venezuelan palm savanna were contrasted in terms of growth phase (epiphyte and tree) and season (dry and wet). The study was motivated by the question of how C3 hemiepiphytes accommodate the marked change in rooting environment associated with a life history of epiphytic establishment followed by substantial root development in the soil. During the dry season, stomatal opening in epiphytic plants occurred only during the early morning, maximum stomatal conductances were 5 to 10-fold lower, and midday leaf water potentials were 0.5–0.8 MPa higher (less negative) than in conspecific trees. Watering epiphytes of F. pertusa during the dry season led to stomatal conductances comparable to those exhibited by conspecific trees, but midday leaf water potentials were unchanged. During the rainy season, epiphytes had lower stomatal conductances than conspecific trees, but leaf water potentials were similar between the two growth phases. There were no differences in ¹³C between the two growth phases for leaves produced in either season. Substrate water availability differed between growth phases; tree roots extended down to the permanent water table, while roots of epiphytic plants were restricted to material accumulated behind the persistent leaf bases of their host palm tree, Copernicia tectorum. Epiphytic substrate moisture contents were variable during both seasons, indicating both the availability of some moisture during the dry season and the possibility of intermittent depletion during the rainy season. Epiphytic strangler figs appear to rely on a combination of strong stomatal control, maintenance of high leaf water potentials, and perhaps some degree of stem water storage to cope with the fluctuating water regime of the epiphytic environment.     

Comparative anatomy of Sirhookera (Orchidaceae) growing in Western Ghats of southern India

We compared the anatomical characteristics of vegetative organs, peduncle and mycorrhizal morphology of the two known species of Sirhookera (Epidendroideae, Orchidaceae) to identify anatomical markers for identification and the ecological adaptations of these species. The leaves are hypostomatic bearing tetracytic stomata and the walls of subsidiary cells are smooth in Sirhookera lanceolata and undulate in Sirhookera latifolia. On the adaxial and abaxial surfaces the leaves are covered by a thick cuticle. The hypodermis is dimorphic and present on both sides of the leaf; chlorenchyma is homogenous and the vascular bundles are collateral. The rhizome of Sirhookera possesses a single-layered epidermis, thick cuticle, thin-walled parenchymatous ground tissue containing starch grains and scattered collateral vascular bundles. A thick-walled sclerenchymatous band separates the cortex from the parenchymatous ground tissue comprising of banded cells in the peduncle. Starch grains are present in the ground tissue of the S. latifolia peduncle. The roots consist of the velamen, ∩-thickened exodermis, thin-walled cortex consisting of water-storage cells, O-thickened endodermis and a vascular cylinder with parenchymatous pith. Starch grains are present in the root cortical cells of S. lanceolata but absent in S. latifolia. Fungal pelotons that aids in nutrient acquisition were observed in the root cortical region of both species. The study revealed significant differences between the anatomical characteristics of the two species and that most of the anatomical features of Sirhookera relate to their ecological adaptations.