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Multiple resistance mechanisms associated with low pirimifos-methyl resistance in Culex pipiens pipiens in three populations of Tunisia

Tabbabi A, Daaboub J, Laamari A, Ben-Cheikh R, Feriani M, Boubaker C, et al.

Trop Biomed, 2018 Dec 01;35(4):1107-1114.
PMID: 33601857

The aim of this study was to evaluate the resistance status of Culex pipiens pipiens to pirimiphos-methyl insecticide. Three field populations of mosquitoes were collected from Tunisia and analyzed in laboratory. The samples studied showed low level of resistance not exceeding 5-folds. The low resistance recorded is particularly interesting, because it leaves a range of tools useable by vector control services. Both metabolic and target-site resistance mechanisms were identified. Different esterases of high activity including A2-B2, A4-B4 (and/or A5-B5) and B12 were observed in studied field samples using starch electrophoresis although opposite results were found using synergists tests on samples # 1 and 3. The polymorphism of AChE1 (Acetylcholinesterase) was analyzed and three phenotypes were detected: susceptible (ACHE1S, phenotype [SS]), resistant (ACHE1R, phenotype [RR]), and heterozygous (phenotype [RS]) of ACHE1. The resistance of Culex pipiens pipiens to pirimiphos-methyl remains low although the occurrences of multiple resistance mechanisms are able to confer high resistance levels to organophosphate insecticides. Therefore, continuous monitoring of resistance is fundamental for rational use of insecticides and mosquito control programs.

Matched MeSH terms: Plant Leaves
Evaluation of the in vitro antileishmanial activities of bioactive guided fractionations of two medicinal plants

Al Nasr IS

Trop Biomed, 2020 Mar 01;37(1):15-23.
PMID: 33612714

The organisms of the genus Leishmania are flagellated protozoan parasites and are the causative agents of leishmaniasis. This disease is a major health problem, especially in tropical countries. Currently, cutaneous leishmaniasis is treated by chemotherapy using pentavalent antimonials, but these drugs have serious organo-toxicity, drug resistance on several occasions, and low efficiency in controlling the infection. The present work is carried out to evaluate the in vitro antileishmanial activity of methanolic extracts and phytochemical fractions of two plants ethnobotanically used against leishmaniasis and skin infection, Calotropis procera and Rhazya stricta leaves against Leishmania major promastigote and amastigote stages and cytotoxicity against the Vero cell line. The leaves of C. procera and R. stricta were extracted with methanol and fractionated by petroleum ether, chloroform, ethyl acetate, n-butanol, and water. The methanolic extracts of the leaves of C. procera and R. stricta exhibited antileishmanial activity against L. major promastigotes with IC50 values of 66.8 and 42.4 µg mL-1, respectively. While their CC50 2.3 and 298 µg mL-1 and their SI 0.03 and 7.03 respectively. However, the fractionations of the methanolic extract of C. procera leaves revealed antiparasitic activity against both L. major promastigote and amastigote stages in vitro, which significantly increased with polarity with the exception of n-butanol. Hence the best activity was revealed by the water fraction (IC50 of 26.3 and 29.0 µg mL-1) for the two stages. In conclusion, further phytochemical investigation should be performed for the C. procera water extract in terms of antileishmanial active ingredient isolation that may enhance the possibility of avoiding toxic substances and overcome the low SI (1.1 and 1.01).

Matched MeSH terms: Plant Leaves/chemistry
Influence of Nigella sativa seeds, Rosmarinus officinalis leaves and their combination on growth performance, immune response and rumen metabolism in Dorper lambs

Odhaib KJ, Adeyemi KD, Ahmed MA, Jahromi MF, Jusoh S, Samsudin AA, et al.

Trop Anim Health Prod, 2018 Jun;50(5):1011-1023.
PMID: 29654500 DOI: 10.1007/s11250-018-1525-7

The objective of this study was to determine the effects of dietary supplementation of Nigella sativa L. seeds, Rosmarinus officinalis L. leaves and their combination on rumen metabolism, nutrient intake and digestibility, growth performance, immune response and blood metabolites in Dorper lambs. Twenty-four entire male Dorper lambs (18.68 ± 0.6 kg, 4-5 months old) were randomly assigned to a concentrate mixture containing on a dry matter basis either, no supplement (control, T1), 1% R. officinalis leaves (T2), 1% N. sativa seeds (T3) or 1% R. officinalis leaves +1% N. sativa seeds (T4). The lambs had ad libitum access to urea-treated rice straw (UTRS) and were raised for 90 days. Supplemented lambs had greater (P plants in ruminant nutrition.

Matched MeSH terms: Plant Leaves/chemistry*
Fulltext Effects of dietary Kleinhovia hospita and Leucaena leucocephala leaves on rumen fermentation and microbial population in goats fed treated rice straw

Ahmed MA, Adeyemi KD, Jahromi MF, Jusoh S, Alimon AR, Samsudin AA

Trop Anim Health Prod, 2017 Dec;49(8):1749-1756.
PMID: 28849307 DOI: 10.1007/s11250-017-1388-3

The effects of partial replacement of dietary protein by forages on rumen fermentation and microbiology in goats were examined. Four fistulated Boer bucks were used in a 4 × 4 Latin square design. The goats were fed 60% of urea-treated rice straw and 40% dietary treatment (Kleinhovia hospita (KH), Leucaena leucocephala (LL), mixture of K. hospita with L. leucocephala (KHLL)) and concentrate as the control. Rumen fluid from the animals was collected at 0, 2, 4, 6, and 12 h postprandial for analysis. The KHLL diet had a greater (P

Matched MeSH terms: Plant Leaves/metabolism
The process-based stand growth model Formix 3-Q applied in a GIS environment for growth and yield analysis in a tropical rain forest

Ditzer T, Glauner R, Förster M, Köhler P, Huth A

Tree Physiol, 2000 Mar;20(5_6):367-381.
PMID: 12651452

Managing tropical rain forests is difficult because few long-term field data on forest growth and the impact of harvesting disturbance are available. Growth models may provide a valuable tool for managers of tropical forests, particularly if applied to the extended forest areas of up to 100,000 ha that typically constitute the so-called forest management units (FMUs). We used a stand growth model in a geographic information system (GIS) environment to simulate tropical rain forest growth at the FMU level. We applied the process-based rain forest growth model Formix 3-Q to the 55,000 ha Deramakot Forest Reserve (DFR) in Sabah, Malaysia. The FMU was considered to be composed of single and independent small-scale stands differing in site conditions and forest structure. Field data, which were analyzed with a GIS, comprised a terrestrial forest inventory, site and soil analyses (water, nutrients, slope), the interpretation of aerial photographs of the present vegetation and topographic maps. Different stand types were determined based on a classification of site quality (three classes), slopes (four classes), and present forest structure (four strata). The effects of site quality on tree allometry (height-diameter curve, biomass allometry, leaf area) and growth (increment size) are incorporated into Formix 3-Q. We derived allometric relations and growth factors for different site conditions from the field data. Climax forest structure at the stand level was shown to depend strongly on site conditions. Simulated successional pattern and climax structure were compared with field observations. Based on the current management plan for the DFR, harvesting scenarios were simulated for stands on different sites. The effects of harvesting guidelines on forest structure and the implications for sustainable forest management at Deramakot were analyzed. Based on the stand types and GIS analysis, we also simulated undisturbed regeneration of the logged-over forest in the DFR at the FMU level. The simulations predict slow recovery rates, and regeneration times far exceeding 100 years.

Matched MeSH terms: Plant Leaves
Changes in shoot allometry with increasing tree height in a tropical canopy species, Elateriospermum tapos

Osada N, Takeda H, Furukawa A, Awang M

Tree Physiol, 2002 Jun;22(9):625-32.
PMID: 12069918

Allometry of shoot extension units (hereafter termed "current shoots") was analyzed in a Malaysian canopy species, Elateriospermum tapos Bl. (Euphorbiaceae). Changes in current shoot allometry with increasing tree height were related to growth and maintenance of tree crowns. Total biomass, biomass allocation ratio of non-photosynthetic to photosynthetic organs, and wood density of current shoots were unrelated to tree height. However, shoot structure changed with tree height. Compared with short trees, tall trees produced current shoots of the same mass but with thicker and shorter stems. Current shoots with thin and long stems enhanced height growth in short trees, whereas in tall trees, thick and short current shoots may reduce mechanical and hydraulic stresses. Furthermore, compared with short trees, tall trees produced current shoots with more leaves of lower dry mass, smaller area, and smaller specific leaf area (SLA). Short trees adapted to low light flux density by reducing mutual shading with large leaves having a large SLA. In contrast, tall trees reduced mutual shading within a shoot by producing more small leaves in distal than in proximal parts of the shoot stem. The production of a large number of small leaves promoted light penetration into the dense crowns of tall trees. All of these characteristics suggest that the change in current shoot structure with increasing tree height is adaptive in E. tapos, enabling short trees to maximize height growth and tall trees to maximize light capture.

Matched MeSH terms: Plant Leaves/anatomy & histology; Plant Leaves/physiology
Influence of irradiance on water relations and carbon flux during rooting of Shorea leprosula leafy stem cuttings

Aminah H, McP Dick J, Grace J

Tree Physiol, 1997 Jul;17(7):445-52.
PMID: 14759836

Single-node leafy stem cuttings of Shorea leprosula Miq. were subjected to a high, intermediate or low irradiance treatment for 16 weeks in an enclosed mist propagation system. Before rooting, maximum photosynthesis of the cuttings occurred at an irradiance of 400 micro mol m(-2) s(-1). Although none of the irradiance treatments affected the number of roots produced per cutting, the numbers of cuttings that formed roots were 50 and 30% in the high irradiance (diurnal range of 0-658 micro mol m(-2) s(-1)) and low irradiance (diurnal range of 0-98 micro mol m(-2) s(-1)) treatments, respectively, compared with 62% in the intermediate irradiance treatment (diurnal range of 0-360 micro mol m(-2) s(-1)). Low rooting frequency of cuttings in the high irradiance treatment was associated with water deficits (maximum leaf-to-air vapor pressure deficit (VPD) = 3.6 kPa), whereas cuttings in the low irradiance treatment had a low rooting frequency because they were below the light compensation point most of the time. In the intermediate irradiance treatment, cuttings withstood a daily maximum VPD of 1-2 kPa and recovered overnight from the previous day's deficit, as indicated by higher relative water content (RWC) and stomatal conductance (g(s)) in the morning than in the previous afternoon and evening. Higher RWC and g(s) of cuttings in all treatments on Days 14 and 21 compared with Day 8 probably indicated recovery from water deficit following severance and insertion of the cuttings in rooting medium. There were negative relationships between stem volume of cuttings and both number of cuttings that rooted and number of roots per cutting.

Matched MeSH terms: Plant Leaves
Diurnal changes in leaf gas exchange characteristics in the uppermost canopy of a rain forest tree, Dryobalanops aromatica Gaertn. f

Ishida A, Toma T, Matsumoto Y, Yap SK, Maruyama Y

Tree Physiol, 1996 Sep;16(9):779-85.
PMID: 14871685

Dryobalanops aromatica Gaertn. f. is a major tropical canopy species in lowland tropical rain forests in Peninsular Malaysia. Diurnal changes in net photosynthetic rate (A) and stomatal conductance to water vapor (g(s)) were measured in fully expanded young and old leaves in the uppermost canopy (35 m above ground). Maximum A was 12 and 10 micro mol m(-2) s(-1) in young and old leaves, respectively; however, because of large variation in A among leaves, mean maximum A in young and old leaves was only 6.6 and 5.5 micro mol m(-2) s(-1), respectively. Both g(s) and A declined in young leaves when T(leaf) exceeded 34 degrees C and leaf-to-air vapor pressure deficit (DeltaW) exceeded 0.025, whereas in old leaves, g(s) and A did not start to decline until T(leaf) and DeltaW exceeded 36 degrees C and 0.035, respectively. Under saturating light conditions, A was linearly related to g(s). The coefficient of variation (CV) for the difference between the CO(2) concentrations of ambient air and the leaf intercellular air space (C(a) - C(i)) was smaller than the CV for A or g(s), suggesting that maximum g(s) was mainly controlled by mesophyll assimilation (A/C(i)). Minimum C(i)/C(a) ratios were relatively high (0.72-0.73), indicating a small drought-induced stomatal limitation to A and non-conservative water use in the uppermost canopy leaves.

Matched MeSH terms: Plant Leaves
Effects of rainfall exclusion on leaf gas exchange traits and osmotic adjustment in mature canopy trees of Dryobalanops aromatica (Dipterocarpaceae) in a Malaysian tropical rain forest

Inoue Y, Ichie T, Kenzo T, Yoneyama A, Kumagai T, Nakashizuka T

Tree Physiol, 2017 10 01;37(10):1301-1311.
PMID: 28541561 DOI: 10.1093/treephys/tpx053

Climate change exposes vegetation to unusual levels of drought, risking a decline in productivity and an increase in mortality. It still remains unclear how trees and forests respond to such unusual drought, particularly Southeast Asian tropical rain forests. To understand leaf ecophysiological responses of tropical rain forest trees to soil drying, a rainfall exclusion experiment was conducted on mature canopy trees of Dryobalanops aromatica Gaertn.f. (Dipterocarpaceae) for 4 months in an aseasonal tropical rain forest in Sarawak, Malaysia. The rainfall was intercepted by using a soft vinyl chloride sheet. We compared the three control and three treatment trees with respect to leaf water use at the top of the crown, including stomatal conductance (gsmax), photosynthesis (Amax), leaf water potential (predawn: Ψpre; midday: Ψmid), leaf water potential at turgor loss point (πtlp), osmotic potential at full turgor (π100) and a bulk modulus of elasticity (ε). Measurements were taken using tree-tower and canopy-crane systems. During the experiment, the treatment trees suffered drought stress without evidence of canopy dieback in comparison with the control trees; e.g., Ψpre and Ψmid decreased with soil drying. Minimum values of Ψmid in the treatment trees decreased during the experiment, and were lower than πtlp in the control trees. However, the treatment trees also decreased their πtlp by osmotic adjustment, and the values were lower than the minimum values of their Ψmid. In addition, the treatment trees maintained gs and Amax especially in the morning, though at midday, values decreased to half those of the control trees. Decreasing leaf water potential by osmotic adjustment to maintain gs and Amax under soil drying in treatment trees was considered to represent anisohydric behavior. These results suggest that D. aromatica may have high leaf adaptability to drought by regulating leaf water consumption and maintaining turgor pressure to improve its leaf water relations.

Matched MeSH terms: Plant Leaves/physiology*
Changes in photosynthesis and leaf characteristics with tree height in five dipterocarp species in a tropical rain forest

Kenzo T, Ichie T, Watanabe Y, Yoneda R, Ninomiya I, Koike T

Tree Physiol, 2006 Jul;26(7):865-73.
PMID: 16585032

Variations in leaf photosynthetic, morphological and biochemical properties with increasing plant height from seedlings to emergent trees were investigated in five dipterocarp species in a Malaysian tropical rain forest. Canopy openness increased significantly with tree height. Photosynthetic properties, such as photosynthetic capacity at light saturation, light compensation point, maximum rate of carboxylation and maximum rate of photosynthetic electron transport, all increased significantly with tree height. Leaf morphological and biochemical traits, such as leaf mass per area, palisade layer thickness, nitrogen concentration per unit area, chlorophyll concentration per unit dry mass and chlorophyll to nitrogen ratio, also changed significantly with tree height. Leaf properties had simple and significant relationships with tree height, with few intra- and interspecies differences. Our results therefore suggest that the photosynthetic capacity of dipterocarp trees depends on tree height, and that the trees adapt to the light environment by adjusting their leaf morphological and biochemical properties. These results should aid in developing models that can accurately estimate carbon dioxide flux and biomass production in tropical rain forests.

Matched MeSH terms: Plant Leaves/anatomy & histology; Plant Leaves/metabolism; Plant Leaves/physiology
Patchy stomatal behavior during midday depression of leaf CO₂ exchange in tropical trees

Kamakura M, Kosugi Y, Takanashi S, Matsumoto K, Okumura M, Philip E

Tree Physiol, 2011 Feb;31(2):160-8.
PMID: 21383025 DOI: 10.1093/treephys/tpq102

We investigated effects of heterogeneous stomatal behavior on diurnal patterns of leaf gas exchange in 10 tree species. Observations were made in middle and upper canopy layers of potted tropical rainforest trees in a nursery at the Forest Research Institute Malaysia. Measurements were taken from 29 January to 3 February 2010. We measured in situ diurnal changes in net photosynthetic rate and stomatal conductance in three leaves of each species under natural light. In both top-canopy and sub-canopy species, midday depression of net assimilation rate occurred in late morning. Numerical analysis showed that patchy bimodal stomatal behavior occurred only during midday depression, suggesting that the distribution pattern of stomatal apertures (either uniform or non-uniform stomatal behavior) varies flexibly within single days. Direct observation of stomatal aperture using Suzuki's Universal Micro-Printing (SUMP) method demonstrated midday patchy stomatal closure that fits a bimodal pattern in Shorea leprosula Miq., Shorea macrantha Brandis. and Dipterocarpus tempehes V.Sl. Inhibition of net assimilation rate and stomatal conductance appears to be a response to changes in vapor pressure deficit (VPD). Variable stomatal closure with increasing VPD is a mechanism used by a range of species to prevent excess water loss from leaves through evapotranspiration (viz., inhibition of midday leaf gas exchange). Bimodal stomatal closure may occur among adjacent stomata within a single patch, rather than among patches on a single leaf. Our results suggest the occurrence of patches at several scales within single leaves. Further analysis should consider variable spatial scales in heterogeneous stomatal behavior between and within patches and within single leaves.

Matched MeSH terms: Plant Leaves/metabolism
Midday depression of leaf CO2 exchange within the crown of Dipterocarpus sublamellatus in a lowland dipterocarp forest in Peninsular Malaysia

Kosugi Y, Takanashi S, Matsuo N, Nik AR

Tree Physiol, 2009 Apr;29(4):505-15.
PMID: 19203974 DOI: 10.1093/treephys/tpn041

We observed diurnal and seasonal patterns of leaf-scale gas exchange within the crown of a Dipterocarpus sublamellatus Foxw. tree growing in a lowland dipterocarp forest at Pasoh, Peninsular Malaysia. Observations were carried out nine times over 6 years, from September 2002 to December 2007. Observation periods included both wet and mild-dry periods, and natural and saturated photosynthetic photon flux density (PPFD) light conditions. In situ measurements of the diurnal change in net photosynthetic rate and in stomatal conductance were carried out on canopy leaves of a 40-m-tall D. sublamellatus tree, which was accessed from a canopy corridor. A diurnal change in electron transport rate was observed under saturated PPFD conditions. The maximum net assimilation rate was approximately 10 micromol m(-2) s(-1). There was a clear inhibition of the net assimilation rate coupled with stomatal closure after late morning and this inhibition occurred year-round. Although the electron transport rate decreased alongside this inhibition, it sometimes followed on. Numerical analysis showed that the main factor in the inhibition of the net assimilation rate was patchy bimodal stomatal closure, which occurred in both mild-dry and wet periods. The midday depression occurred year-round, though there are fluctuations in soil moisture during the mild-dry and wet periods. The magnitude of the inhibition was not related to soil water content but was related to vapor pressure deficit (VPD): that is, whether the days were sunny and hot or cloudy and cool. On cloudy, cool days in the wet period, the net photosynthesis was only moderately inhibited, but it still decreased in the afternoon and was coupled with patchy stomatal closure, even in quite moderate VPD, leaf temperature and PPFD conditions. Our results suggest that patchy stomatal closure signaled by the increase in VPD, in transpiration and by circadian rhythms, was the key factor in constraining midday leaf gas exchange of the D. sublamellatus canopy leaves.

Matched MeSH terms: Plant Leaves/metabolism
Age- and size-related changes in physiological characteristics and chemical composition of Acer pseudoplatanus and Fraxinus excelsior trees

Abdul-Hamid H, Mencuccini M

Tree Physiol, 2009 Jan;29(1):27-38.
PMID: 19203930 DOI: 10.1093/treephys/tpn001

Forest growth is an important factor both economically and ecologically, and it follows a predictable trend with age. Generally, growth accelerates as canopies develop in young forests and declines substantially soon after maximum leaf area is attained. The causes of this decline are multiple and may be linked to age- or size-related processes, or both. Our objective was to determine the relative effects of tree age and tree size on the physiological attributes of two broadleaf species. As age and size are normally coupled during growth, an approach based on grafting techniques to separate the effects of size from those of age was adopted. Genetically identical grafted seedlings were produced from scions taken from trees of four age classes, ranging from 4 to 162 years. We found that leaf-level net photosynthetic rate per unit of leaf mass and some other leaf structural and biochemical characteristics had decreased substantially with increasing size of the donor trees in the field, whereas other gas exchange parameters expressed on a leaf area basis did not. In contrast, these parameters remained almost constant in grafted seedlings, i.e., scions taken from donor trees with different meristematic ages show no age-related trend after they were grafted onto young rootstocks. In general, the results suggested that size-related limitations triggered the declines in photosynthate production and tree growth, whereas less evidence was found to support a role of meristematic age.

Matched MeSH terms: Plant Leaves/physiology; Plant Leaves/chemistry
Occurrence of stomatal patchiness and its spatial scale in leaves from various sizes of trees distributed in a South-east Asian tropical rainforest in Peninsular Malaysia

Kamakura M, Kosugi Y, Takanashi S, Uemura A, Utsugi H, Kassim AR

Tree Physiol, 2015 Jan;35(1):61-70.
PMID: 25595752 DOI: 10.1093/treephys/tpu109

In this study, we demonstrated the occurrence of stomatal patchiness and its spatial scale in leaves from various sizes of trees grown in a lowland dipterocarp forest in Peninsular Malaysia. To evaluate the patterns of stomatal behavior, we used three techniques simultaneously to analyze heterobaric or homobaric leaves from five tree species ranging from 0.6 to 31 m in height: (i) diurnal changes in chlorophyll fluorescence imaging, (ii) observation and simulation of leaf gas-exchange rates and (iii) a pressure-infiltration method. Measurements were performed in situ with 1000 or 500 μmol m(-2) s(-1) photosynthetic photon flux density. Diurnal patterns in the spatial distribution of photosynthetic electron transport rate (J) mapped from chlorophyll fluorescence images, a comparison of observed and simulated leaf gas-exchange rates, and the spatial distribution of stomatal apertures obtained from the acid-fuchsin-infiltrated area showed that patchy stomatal closure coupled with severe midday depression of photosynthesis occurred in Neobalanocarpus heimii (King) Ashton, a higher canopy tree with heterobaric leaves due to the higher leaf temperature and vapor pressure deficit. However, subcanopy or understory trees showed uniform stomatal behavior throughout the day, although they also have heterobaric leaves. These results suggest that the occurrence of stomatal patchiness is determined by tree size and/or environmental conditions. The analysis of spatial scale by chlorophyll fluorescence imaging showed that several adjacent anatomical patches (lamina areas bounded by bundle-sheath extensions within the lamina) may co-operate for the distributed patterns of J and stomatal apertures.

Matched MeSH terms: Plant Leaves/anatomy & histology; Plant Leaves/physiology
High CO2 concentration increases relative leaf carbon gain under dynamic light in Dipterocarpus sublamellatus seedlings in a tropical rain forest, Malaysia

Tomimatsu H, Iio A, Adachi M, Saw LG, Fletcher C, Tang Y

Tree Physiol, 2014 Sep;34(9):944-54.
PMID: 25187569 DOI: 10.1093/treephys/tpu066

Understory plants in tropical forests often experience a low-light environment combined with high CO2 concentration. We hypothesized that the high CO2 concentration may compensate for leaf carbon loss caused by the low light, through increasing light-use efficiency of both steady-state and dynamic photosynthetic properties. To test the hypothesis, we examined CO2 gas exchange in response to an artificial lightfleck in Dipterocarpus sublamellatus Foxw. seedlings under contrasting CO2 conditions: 350 and 700 μmol CO2 mol(-1) air in a tropical rain forest, Pasoh, Malaysia. Total photosynthetic carbon gain from the lightfleck was about double when subjected to the high CO2 when compared with the low CO2 concentration. The increase of light-use efficiency in dynamic photosynthesis contributed 7% of the increased carbon gain, most of which was due to reduction of photosynthetic induction to light increase under the high CO2. The light compensation point of photosynthesis decreased by 58% and the apparent quantum yield increased by 26% at the high CO2 compared with those at the low CO2. The study suggests that high CO2 increases photosynthetic light-use efficiency under both steady-state and fluctuating light conditions, which should be considered in assessing the leaf carbon gain of understory plants in low-light environments.

Matched MeSH terms: Plant Leaves/metabolism
Patchy stomatal behavior in broad-leaved trees grown in different habitats

Takanashi S, Kosugi Y, Matsuo N, Tani M, Ohte N

Tree Physiol, 2006 Dec;26(12):1565-78.
PMID: 17169896

Effects of heterogeneity in stomatal behavior on gas-exchange characteristics of leaves from four tree species growing in different climates, including temperate, tropical monsoon and tropical rain forest, were investigated by combining gas-exchange measurements and the pressure-infiltration method. Field observations indicated linear relationships between whole-leaf conductance and the ratio of infiltrated to non-infiltrated leaf area (open stomata area) in Dipterocarpus sublamellatus Foxw. and Neobalanocarpus heimii (King) Ashton in a tropical rain forest in Peninsular Malaysia, whereas the ratio of infiltrated to non-infiltrated area rapidly increased up to the whole-leaf conductance at which the entire leaf was infiltrated in Cinnamomum camphora Sieb. in a temperate evergreen forest in Japan and in Azadirachta indica Juss. in a tropical monsoon area in Thailand. These results strongly suggest small ranges in bell-shaped stomatal conductance distributions in C. camphora and A. indica and bimodal stomatal conductance distributions in D. sublamellatus and N. heimii. The values of normalized maximum carboxylation rate at 25 degrees C (V(cmax25)) derived from gas-exchange measurements were not constant, but decreased with decreasing whole-leaf conductance in D. sublamellatus and N. heimii. A gas-exchange model analysis revealed a linear relationship between whole-leaf conductance and the ratio of infiltrated to non-infiltrated leaf area for bimodal stomatal conductance distributions, whereas for bell-shaped distributions, the relationships were nonlinear. Midday depression of apparent V(cmax25) in these species was mainly caused by bimodal stomatal closure. The bimodal stomatal distribution model could also explain diurnal changes in photosynthetic assimilation and transpiration rates in these species.

Matched MeSH terms: Plant Leaves/physiology*
Interspecific variation of photosynthesis and leaf characteristics in canopy trees of five species of Dipterocarpaceae in a tropical rain forest

Kenzo T, Ichie T, Yoneda R, Kitahashi Y, Watanabe Y, Ninomiya I, et al.

Tree Physiol, 2004 Oct;24(10):1187-92.
PMID: 15294766

Photosynthetic rate, nitrogen concentration and morphological properties of canopy leaves were studied in 18 trees, comprising five dipterocarp species, in a tropical rain forest in Sarawak, Malaysia. Photosynthetic rate at light saturation (Pmax) differed significantly across species, varying from 7 to 18 micro mol m(-2) s(-1). Leaf nitrogen concentration and morphological properties, such as leaf blade and palisade layer thickness, leaf mass per area (LMA) and surface area of mesophyll cells per unit leaf area (Ames/A), also varied significantly across species. Among the relationships with leaf characteristics, Pmax had the strongest correlation with leaf mesophyll parameters, such as palisade cell layer thickness (r2 = 0.76, P < 0.001) and Ames/A (r2 = 0.73, P < 0.001). Leaf nitrogen concentration and Pmax per unit area also had a significant but weaker correlation (r2 = 0.46, P < 0.01), whereas Pmax had no correlation, or only weakly significant correlations, with leaf blade thickness and LMA. Shorea beccariana Burck, which had the highest P(max) of the species studied, also had the thickest palisade layer, with up to five or more layers. We conclude that interspecific variation in photosynthetic capacity in tropical rain forest canopies is influenced more by leaf mesophyll structure than by leaf thickness, LMA or leaf nitrogen concentration.

Matched MeSH terms: Plant Leaves/anatomy & histology; Plant Leaves/physiology*
Leaf thermotolerance of Hevea brasiliensis clones: intra- versus interclonal variation and relationships with other functional traits

Hazir MHM, Gloor E, Docherty E, Galbraith D

Tree Physiol, 2024 Feb 11;44(3).
PMID: 38349811 DOI: 10.1093/treephys/tpae022

Land surface temperature is predicted to increase by 0.2 °C per decade due to climate change, although with considerable regional variability, and heatwaves are predicted to increase markedly in the future. These changes will affect where crops can be grown in the future. Understanding the thermal limits of plant physiological functioning and how flexible such limits are is thus important. Here, we report on the measurements of a core foliar thermotolerance trait, T50, defined as the temperature at which the maximum quantum yield (Fv/Fm) of photosystem II declines by 50%, across nine different Malaysian Hevea brasiliensis clones. We explore the relative importance of interclonal versus intraclonal variation in T50 as well as its association with leaf and hydraulic traits. We find very low variation in T50 within individual clones (mean intraclonal coefficient of variation (CoV) of 1.26%) and little variation across clones (interclonal CoV of 2.1%). The interclonal variation in T50 was lower than for all other functional traits considered. The T50 was negatively related to leaf mass per area and leaf dry matter content, but it was not related to hydraulic traits such as embolism resistance (P50) or hydraulic safety margins (HSM50). The range of T50 observed (42.9-46.2 °C) is well above the current maximum air temperatures Tmax,obs (T50 - Tmax,obs >5.8 °C), suggesting that H. brasiliensis is likely thermally safe in this south-east Asian region of Malaysia.

Matched MeSH terms: Plant Leaves/physiology
Fulltext Sub-chronic toxicological evaluation of cleistanthin A and cleistanthin B from the leaves of Cleistanthus collinus (Roxb.)

Parasuraman S, Raveendran R, Rajesh NG, Nandhakumar S

Toxicol Rep, 2014;1:596-611.
PMID: 28962273 DOI: 10.1016/j.toxrep.2014.08.006

OBJECTIVE: To investigate the toxicological effects of cleistanthin A and cleistanthin B using sub-chronic toxicity testing in rodents.
METHOD: Cleistanthins A and B were isolated from the leaves of Cleistanthus collinus. Both the compounds were administered orally for 90 days at the concentration of 12.5, 25 and 50 mg/kg, and the effects on blood pressure, biochemical parameters and histology were assessed. The dose for sub-chronic toxicology was determined by fixed dose method according to OECD guidelines.
RESULT: Sub-chronic toxicity study of cleistanthins A and B spanning over 90 days at the dose levels of 12.5, 25 and 50 mg/kg (once daily, per oral) revealed a significant dose dependant toxic effect in lungs. The compounds did not have any effect on the growth of the rats. The food and water intake of the animals were also not affected by both cleistanthins A and B. Both the compounds did not have any significant effect on liver and renal markers. The histopathological analysis of both cleistanthins A and B showed dose dependent morphological changes in the brain, heart, lung, liver and kidney. When compared to cleistanthin A, cleistanthin B had more toxic effect in Wistar rats. Both the compounds have produced a dose dependent increase of corpora amylacea in brain and induced acute tubular necrosis in kidneys. In addition, cleistanthin B caused spotty necrosis of liver in higher doses.
CONCLUSION: The present study concludes that both cleistanthin A and cleistanthin B exert severe toxic effects on lungs, brain, liver, heart and kidneys. They do not cause any significant pathological change in the reproductive system; neither do they induce neurodegenerative changes in brain. When compared to cleistanthin A, cleistanthin B is more toxic in rats.

Matched MeSH terms: Plant Leaves
Suppressing growth, migration, and invasion of human hepatocellular carcinoma HepG2 cells by Catharanthus roseus‑silver nanoparticles

Azhar NA, Ghozali SZ, Abu Bakar SA, Lim V, Ahmad NH

Toxicol In Vitro, 2020 Sep;67:104910.
PMID: 32526345 DOI: 10.1016/j.tiv.2020.104910

Application of silver nanoparticles serves as a new approach in cancer treatment due to its unique features. Biosynthesis of silver nanoparticles using plant is advantageous since they are easily accessible, nontoxic and produce quicker reaction compared to other methods. To evaluate the cytotoxicity, mechanism of cell death and DNA damage of biosynthesized Catharanthus roseus-silver nanoparticles on human liver cancer (HepG2) cells. The antiproliferative activity of Catharanthus roseus‑silver nanoparticles was measured using MTT assay. The cytotoxic effects were further evaluated by measuring nitric oxide and reactive oxygen species (ROS). The mechanism of cell death was determined by annexin-FITC/propidium iodide, mitochondrial membrane potential (MMP) and cell cycle assays. The assessment of DNA damage was evaluated using Comet assay method. The uptake of the nanoparticles were evaluated by Transmission Electron Microscopy (TEM). Catharanthus roseus‑silver nanoparticles has inhibited the proliferation of HepG2 cells in a time-dependent manner with a median IC50 value of 3.871 ± 0.18 μg/mL. The concentration of nitrite and ROS were significantly higher than control. The cell death was due to apoptosis associated with MMP loss, cell cycle arrest, and extensive DNA damage. TEM analysis indicated the presence of free nanoparticles and endosomes containing the nanoparticles. The findings show that Catharanthus roseus‑silver nanoparticles have produced cytotoxic effects on HepG2 cells and thus may have a potential to be used as an anticancer treatment, particularly for hepatocellular carcinoma.

Matched MeSH terms: Plant Leaves

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