Leaf Microstructure Research Articles

Micropatterning of hybrid polydimethylsiloxane for replica leaves

Artificial surfaces representing key features of plant leaves, such as surface topography and nutrient availability, promise to play an important role in phyllosphere microbiology. While polydimethylsiloxane (PDMS) constitutes an ideal candidate for leaf replica materials, its inherent hydrophobicity limits the diffusion of aqueous liquids. To solve this, we added superabsorbent polymer fillers Carbopol® and PermulenTM to PDMS, to increase the diffusion of aqueous liquids. We demonstrate that hybrid PDMS retains its capability to resolve leaf microstructures, while exhibiting similar contact angles to PDMS and the abaxial surface of Arabidopsis thaliana leaves. Water diffusion and mass flow through hybrid PDMS membranes were consistently higher than PDMS over the 144 h experimental duration. In addition, bacteria distribution patterns on hybrid PDMS were similar to those observed on A. thaliana leaves. However, the patterns observed on hybrid PDMS appeared to be influenced by the increase in wettability. These findings demonstrate that hybrid PDMS replicas can be used as an artificial surface to study bacterial behavior and microbe-microbe interactions.

Leaf micromorphology of the Persicaria sect. Cephalophilon (Polygonaceae) and its systematic re-evaluation

A comparative study of the leaf microstructures of 19 taxa belonging to the Persicaria sect. Cephalophilon and related four Koenigia taxa was performed by LM and SEM to evaluate their systematic significance. Both amphistomatic and hypostomatic leaves were observed in the taxa studied. The stomatal size ranged from 17.04–41.96 × 13.41–37.30 μm, and stomata on the adaxial side were larger than those on the abaxial side in general. Anomocytic stomata occurred most commonly, but more than one type of stomata was observed on the same surface. Paracytic stomata was found in both Persicaria palmata and P. criopolitana. The epidermal cells usually have straight to sinuate anticlinal cell walls (ACW), and the ACW on the abaxial side of most taxa is much more undulated than that on the adaxial side. Cuticular striation was observed in most of the studied taxa, which was restricted to only the adaxial side. Two types of crystals were observed: druse and prismatic, and seven types of trichome were recognized: five types of non-glandular trichomes (stellate with smooth surface, multiseriate with either smooth or striated surface, and uniseriate with either smooth or papillose surface), and two types of glandular trichomes (peltate and long-stalked pilate). The leaf micromorphology in this study was categorized into five types based on the stomata, epidermis, crystal and trichome, as further systematic significance of the leaf epidermal characters within the P. sect. Cephalophilon are discussed. In addition, we propose a new taxonomic combination in the P. sect. Cephalophilon.

The Influence of Light Intensity and Leaf Movement on Photosynthesis Characteristics and Carbon Balance of Soybean.

In intercropping systems shading conditions significantly impair the seed yield and quality of soybean, and rarely someone investigated the minimum amount of light requirement for soybean growth and development. Therefore, it is an urgent need to determine the threshold light intensity to ensure sustainable soybean production under these systems. An integrated approach combining morphology, physiology, biochemistry and genetic analysis was undertaken to study the light intensity effects on soybean growth and development. A pot experiment was set up in a growth chamber under increasing light intensity treatments of 100 (L100), 200 (L200), 300 (L300), 400 (L400), and 500 (L500) μmol m−2 s−1. Compared with L100, plant height, hypocotyl length, and abaxial leaf petiole angle were decreased, biomass, root:shoot ratio, and stem diameter were increased, extremum was almost observed in L400 and L500. Leaf petiole movement and leaf hyponasty in each treatment has presented a tendency to decrease the leaf angle from L500 to L100. In addition, the cytochrome content (Chl a, Chl b, Car), net photosynthetic rate, chlorophyll fluorescence values of Fv/Fm, /, ETR, ΦPSII, and qP were increased as the light intensity increased, and higher values were noted under L400. Leaf microstructure and chloroplast ultrastructure positively improved with increasing light intensity, and leaf-thickness, palisade, and spongy tissues-thickness were increased by 105, 90, and 370%, under L500 than L100. Moreover, the cross-sectional area of chloroplast (C) outer membrane and starch grains (S), and sectional area ratio (S:C) was highest under L400 and L500, respectively. Compared to L100, the content of starch granules increased by 35.5, 122.0, 157.6, and 145.5%, respectively in L400. The same trends were observed in the enzyme activity of sucrose-synthase, sucrose phosphate synthase, starch synthase, rubisco, phosphoenol pyruvate carboxykinase, and phosphoenol pyruvate phosphatase. Furthermore, sucrose synthesis-related genes were also up-regulated by increasing light intensity, and the highest seed yield and yield related parameters were recorded in the L400. Overall, these results suggested that 400 and 500 μmol m−2 s−1 is the optimum light intensity which positively changed the leaf orientation and adjusts leaf angle to perpendicular to coming light, consequently, soybean plants grow well under prevailing conditions.

Tea leaf’s microstructure and ultrastructure response to low temperature in indicating critical damage temperature

To find out the critical damage temperature of tea leaf, a new method of subzero treatment was provided by fitting the air temperature data from six heavy frost events. Furthermore, the study explored the characteristics of Fuding Dabai tea plant response to low temperature stress of 2, 0, −2, −4, −8, −10 and −15 °C by observing the microstructure and ultrastructure changes of the leaves. All samples were collected in an ambient temperature of 8.6 °C which served as control. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the microstructure and ultrastructure of stomata and mesophyll. SEM observation results indicated that stomata of tea leaves have an obvious low temperature stress when the temperature was lower than −2 °C. The extent of opening of the stomata increased and enhanced guard cell protection of tea leaves against cold injury. However, dehydration, shrinkage and deformation of cells occurred as the temperature decreased from −2 °C to −15 °C. TEM observations showed that the cell nucleus, cell walls, chloroplasts and mitochondria all had normal structure at a temperature of 8.6 °C where the membrane and granum lamella were clearly visible. As the temperature decreased to −2 °C, the membrane system of tea leaf was the first to be damaged and the cell walls became fuzzy. Therefore, the leaf microstructure and ultrastructure showed obvious changes at −2 °C, which might define the critical damage temperature for freeze damage of Fuding Dabai tea. Control strategy based this critical damage temperature is useful for wind machine frost protection in tea fields within the Yangtze River region.

Influence of drought hardening on the resistance physiology of potato seedlings under drought stress

In this paper, the influence of drought hardening on the growth, development, resistance physiology, leaf microstructure and stomatal behavior of potato seedlings under drought stress was studied, and the mechanism of drought hardening improvement of potato seedling drought resistance was elucidated. We found that drought stress had several adverse effects on potato seedlings, yet drought hardening alleviated the decrease in relative water content (RWC), net photosynthetic rate (Pn) and chlorophyll content and inhibited the increase in relative electric conductivity and malondialdehyde (MDA) content. Compared with contrast seedlings, drought-hardened seedlings also had enhanced root vigor, increased antioxidant enzyme activity and higher levels of abscisic acid (ABA), proline (Pro), soluble sugars and polyamines (PAs) under drought stress. In addition, the stomatal density of potato seedling leaves increased significantly, while the leaf area, stomatal size and stomatal aperture decreased with drought hardening treatment. These changes led to reduced leaf transpiration rate (Tr) and improved water utilization efficiency (WUE). The changes in leaf microstructure also had a positive effect on the drought resistance of the drought-hardened potato seedlings. So it can be concluded that through increasing the content of some endogenous hormones, osmotic regulatory substances and the activities of antioxidant enzymes, the resistance physiology of drought-hardened potato seedlings was enhanced.

Superhydrophobic and self-cleaning behavior of Portland cement with lotus-leaf-like microstructure

Nanocasting technique was used to transfer lotus-leaf-like microstructure onto the cement surface. Lotus leaf and Poly (dimethylsiloxane) (PDMS) were used as the origin template and negative template for surface microstructure casting, respectively. The micro papillae were successful replicated on the cement surface with high fidelity to lotus leaf microstructure. Viscosity of cement paste plays an important role in the nanocasting process. Lotus-leaf-like microstructure on cement surface was fabricated when viscosity deceased to 0.09 Pa·S. The equilibrium contact angle is about 140° on superhydrophobic cement surfaces as for the optimal specimen. The Cassie-Baxter model can be used to explain the variation of water contact angle with rough ratio as well as viscosity of cement paste. Measurement of rolling-off contact angle confirmed the superhydrophobic behavior of cement. The self-cleaning properties of the superhydrophobic cement were proved by “T” marker experiment with a potential application in future.

Exploring anatomical controls of C4leaf photosynthesis using a 3D reaction-diffusion model

C4 plants such as maize (Zea mays L.), sugarcane (Saccharum officinarum L.) and sorghum [Sorghum bicolor (L.) Moench.] photosynthesize at a high rate due to a CO2 concentration mechanism (CCM) that accumulates CO2 to saturating concentrations around the carboxylation site of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Transport of CO2 inside a leaf and, therefore, the CCM, is affected by leaf microstructure. Gas transport models with a realistic leaf microstructure help to assess the significance of anatomical features of C4 plants quantitatively for effective CCM. One- and two-dimensional gas transport models, when applied to analyze the gas diffusion in leaves, understate the three-dimensional nature. Here, we present the first 3D reaction-diffusion model for photosynthesis of a C4 leaf. Equations of CO2 transport and bicarbonate diffusion combined with a biochemical model of C4 photosynthesis were discretized over the 3D geometry of a maize leaf tissue. The model could describe the trends in responses of photosynthesis to light and CO2. The CO2 profile in the leaf microstructure was highly heterogeneous. The model suggests that rapid diffusion of CO2 to mesophyll cytosol is essential to achieve a high rate of photosynthesis.

Effects of light intensity on leaf microstructure and growth of rape seedlings cultivated under a combination of red and blue LEDs

The aim of this study was to evaluate the growth of rape (Brassica napus L.) seedlings under different light intensities to select appropriate conditions for cultivation in an indoor system. Seedlings were grown under different light intensities of red and blue light provided by light-emitting diodes (LEDs) and their self-adjustment ability and changes in leaf microstructure were evaluated. Light was supplied by red LEDs with peak wavelengths of 630 (R1) and 660 nm (R2) and by blue LEDs (B) with a peak wavelength of 445 nm (the light intensity ratio of R1:R2:B was 3:3:2), at intensities of 400 (R1R2B400), 300 (R1R2B300), and 200 μmol m−2 s−1 (R1R2B200). Natural solar light served as the control (C). Plant height, stem diameter, root length, leaf area, and dry weight of rape seedlings gradually increased with increasing light intensity. The seedlings in the R1R2B400 treatment grew more vigorously, while those in the R1R2B200 treatment were weaker. The photosynthetic pigment contents did not differ significantly between the R1R2B400 treatment and C, but were significantly lower in the R1R2B300 and R1R2B200 treatments. The highest intercellular CO2 concentration, stomatal conductance, and transpiration rate were in the R1R2B300 treatment. The highest photosynthetic rate was in the R1R2B400 treatment, and was related to more compact leaves, thicker and tidier palisade and spongy tissues, and well-developed chloroplasts. In contrast, the seedlings in the R1R2B200 treatment had disordered mesophyll cells, round chloroplasts, and fractured and fuzzy grana lamellae, all of which inhibited plant growth. In conclusion, the seedlings in the R1R2B400 treatment had well-developed leaves, which favored photosynthesis. Compared with the light intensities below 300 μmol m−2 s−1, the light intensity of 400 μmol m−2 s−1 provided by a combination of red and blue LEDs was beneficial for cultivating strong and healthy rape seedlings in an artificial system.

Bionic anti-adhesive electrode coupled with maize leaf microstructures and TiO2 coating

Designing and fabricating a type of effectively anti-adhesive electrode via coupling the bionic microstructures and TiO2 coating.

Convenient Measurement and Modified Model for Broadleaf Permittivity

The dielectric properties of vegetation reflect the coupling between the electromagnetic and physical properties of the material. Understanding dielectric behavior is essential for remote sensing applications. The traditional approach of measuring broadleaf permittivity involves exerting pressure on stacked leaves, which not only requires a complicated system to measure the pressure but also introduces a degree of uncertainty by changing the internal leaf microstructure. We propose a measurement technique that avoids the aforementioned shortcomings by using a vacuum packaging machine to remove the air from a sample bag, which is the first contribution of this paper. The proposed technique is validated against corn, cotton, and soybean leaf permittivity measurements. The second contribution of this paper involves how temperature is treated when modeling permittivity. The Debye–Cole dual-dispersion model, which is influential in vegetation remote sensing applications, is almost exclusively applied at 22 °C. However, it is assumed that this model can be extrapolated to other temperatures. Our analysis indicates that this model may overestimate permittivity at 28 °C, with mean relative errors (MREs) of up to 22% and 37% for relative permittivity and dielectric loss. Thus, we adopt the structure of the model due to its soundness and modify the model parameters. Overall, we used four different methods, among which the optimal method reduced the MRE by no more than −2.5%.

Feeding behavioral response of cotton aphid, Aphis gossypii, to elevated CO2: EPG test with leaf microstructure and leaf chemistry

AbstractEffect of elevated CO2 on feeding behavior of the cotton aphid, Aphis gossypii (Glover) (Hemiptera: Aphididae), was investigated using electrical penetration graphs (EPG) on cotton, Gossypium hirsutum L. (Malvaceae). Leaf microstructures and foliar soluble constituents were also measured simultaneously to quantify the impact of foliar changes on leaf nutritional quantity and quality, owing to elevated CO2, on stylet penetration and food‐quality plasticity of A. gossypii. Significant increases in fresh body weight, fecundity, and population abundances of A. gossypii were found in elevated CO2 in contrast to ambient CO2. Elevated CO2 influenced the feeding behavior, as evidenced by altered EPG recordings, including the increased non‐penetration period (walking and finding the feeding site), E2<8 min (probes with sustained ingestion of <8 min), and first E2>8 min (first occurrence of probes with sustained ingestion of >8 min), and decreased E2>8 min recordings. Moreover, leaf microstructures were significantly affected by CO2 levels, with thinner upside epidermis (UPE) and thicker underside epidermis (UDE), sponge tissues (ST), and fence tissues under elevated CO2 compared to that in ambient CO2. Therefore, it is expected that A. gossypii spend more time penetrating the thicker leaf UDE and ST when the host plant is exposed to elevated CO2. Furthermore, elevated CO2 significantly enhanced foliar soluble matter, including soluble sugars (SS), free amino acids and fatty acids (FFA), and total soluble matter (TSM), which was congruent with significant increase or decrease in leaf turgor or osmotic potential. Increased leaf turgor and leaf soluble constituents favored ingestion in A. gossypii, resulting in increases in fresh body weight, fecundity, and population abundances under elevated CO2. These feeding behaviors and resulting population growth parameters are consistent with the significant positive correlations between aphid fresh body weight and foliar FFA/TSM, between A. gossypii fecundity and foliar SS of cotton plants, and between the time of E2<8 min recordings and leaf turgor.

Impact of anatomical traits of maize (Zea mays L.) leaf as affected by nitrogen supply and leaf age on bundle sheath conductance

The mechanism of photosynthesis in C4 crops depends on the archetypal Kranz-anatomy. To examine how the leaf anatomy, as altered by nitrogen supply and leaf age, affects the bundle sheath conductance (gbs), maize (Zea mays L.) plants were grown under three contrasting nitrogen levels. Combined gas exchange and chlorophyll fluorescence measurements were done on fully grown leaves at two leaf ages. The measured data were analysed using a biochemical model of C4 photosynthesis to estimate gbs. The leaf microstructure and ultrastructure were quantified using images obtained from micro-computed tomography and microscopy. There was a strong positive correlation between gbs and leaf nitrogen content (LNC) while old leaves had lower gbs than young leaves. Leaf thickness, bundle sheath cell wall thickness and surface area of bundle sheath cells per unit leaf area (Sb) correlated well with gbs although they were not significantly affected by LNC. As a result, the increase of gbs with LNC was little explained by the alteration of leaf anatomy. In contrast, the combined effect of LNC and leaf age on Sb was responsible for differences in gbs between young leaves and old leaves. Future investigations should consider changes at the level of plasmodesmata and membranes along the CO2 leakage pathway to unravel LNC and age effects further.

Infrared microspectroscopic imaging of plant tissues: spectral visualization of Triticum aestivum kernel and Arabidopsis leaf microstructure.

Infrared microspectroscopy is a tool with potential for studies of the microstructure, chemical composition and functionality of plants at a subcellular level. Here we present the use of high-resolution bench top-based infrared microspectroscopy to investigate the microstructure of Triticum aestivum L. (wheat) kernels and Arabidopsis leaves. Images of isolated wheat kernel tissues and whole wheat kernels following hydrothermal processing and simulated gastric and duodenal digestion were generated, as well as images of Arabidopsis leaves at different points during a diurnal cycle. Individual cells and cell walls were resolved, and large structures within cells, such as starch granules and protein bodies, were clearly identified. Contrast was provided by converting the hyperspectral image cubes into false-colour images using either principal component analysis (PCA) overlays or by correlation analysis. The unsupervised PCA approach provided a clear view of the sample microstructure, whereas the correlation analysis was used to confirm the identity of different anatomical structures using the spectra from isolated components. It was then demonstrated that gelatinized and native starch within cells could be distinguished, and that the loss of starch during wheat digestion could be observed, as well as the accumulation of starch in leaves during a diurnal period.

Three-dimensional microscale modelling of CO2 transport and light propagation in tomato leaves enlightens photosynthesis.

We present a combined three-dimensional (3-D) model of light propagation, CO2 diffusion and photosynthesis in tomato (Solanum lycopersicum L.) leaves. The model incorporates a geometrical representation of the actual leaf microstructure that we obtained with synchrotron radiation X-ray laminography, and was evaluated using measurements of gas exchange and leaf optical properties. The combination of the 3-D microstructure of leaf tissue and chloroplast movement induced by changes in light intensity affects the simulated CO2 transport within the leaf. The model predicts extensive reassimilation of CO2 produced by respiration and photorespiration. Simulations also suggest that carbonic anhydrase could enhance photosynthesis at low CO2 levels but had little impact on photosynthesis at high CO2 levels. The model confirms that scaling of photosynthetic capacity with absorbed light would improve efficiency of CO2 fixation in the leaf, especially at low light intensity.

Development of the stomatal complex and leaf surface of Agave angustifolia Haw. ‘Bacanora’ plantlets during the in vitro to ex vitro transition process

Many agaves are economically important plants that have not been genetically improved, mainly due to their long life cycles. Micropropagation offers a means for increasing crop productivity of Agave species; however, an important limitation of this technique is the mortality rate of the in vitro cultured plants during transfer to soil. This is due to the morphological and physiological abnormalities produced by the physical and chemical conditions of in vitro culture. In order to understand these alterations, we investigated the development of the stomatal complex and of the leaf surface of Agave angustifolia shoots cultured under three different in vitro systems (semi-solid media [magenta boxes], permanent immersion [liquid in flasks with a cotton cover] and temporary immersion [BioMINT™ bioreactors]) and during the transition from in vitro to ex vitro conditions (greenhouse, shaded nursery and planted in the field). The apical, middle and basal regions of both the adaxial and abaxial leaf surfaces were analyzed by scanning electron microscopy (SEM) and the quantity and composition of leaf epicuticular waxes were analyzed by gas chromatography mass spectrometry (GC–MS). The leaf microstructure of the plantlets changed considerably through the sequential stages. While only immature stomata were observed in the in vitro phase, they developed to mature functional stomata in the various ex vitro phases. The results presented here indicate that temporary immersion system, may contribute to a pre-adaptation of plantlets, although they do not result in the formation of fully mature and functional stomata. The adaptation in the greenhouse and shaded nurseries is therefore convenient for the development of the plants.

Preparation and hydrophobicities of biomorphic ZnO based on carbon derived from indicalamus leaf template

Some plant leaves possess a superhydrophobicity because of the exclusive structures on their surfaces. Many methods were developed to imitate the leaf structures in order to obtain the superhydrophobic ZnO. However, it is difficult to simulate the natural complex structures through the traditional methods. In the present study, we used an indicalamus leaf as a template to fabricate a superhydrophobic biomorphic ZnO on a carbon substrate (ZnO/C). First, a carbon substrate with a leaf microstructure was obtained by sintering an indicalamus leaf in argon. The biomorphic ZnO/C was then obtained by immersing this carbon substrate into a Zn(NO3)2 solution and again sintering it. This ZnO/C exhibited superhydrophobicity after it was modified with fluorine silane. The water contact angle of the resulting product was 163°, which is similar to that of the indicalamus leaf (159°) and is much higher than that of smooth carbon covered with the same fluorine silane (114°).

An ethanol-based fixation method for anatomical and micro-morphological characterization of leaves of various tree species

The use of formalin constitutes serious health hazards for laboratory workers. We investigated the suitability and performance of the ethanol-based fixative, FineFIX, as a substitute for formalin for anatomical and cellular structure investigations of leaves by light microscopy and for leaf surface and ultrastructural analysis by scanning electron microscopy (SEM). We compared the anatomical features of leaf materials prepared using conventional formalin fixation with the FineFIX. Leaves were collected from ornamental tree species commonly used in urban areas. FineFIX was also compared with glutaraldehyde fixation and air drying normally used for scanning electron microscopy to develop a new method for evaluating leaf morphology and microstructure in three ornamental tree species. The cytological features of the samples processed for histological analysis were well preserved by both fixatives as demonstrated by the absence of nuclear swelling or shrinkage, cell wall detachment or tissue flaking, and good presentation of cytoplasmic vacuolization. In addition, good preservation of surface details and the absence of shrinkage artefacts confirmed the efficacy of FineFIX fixation for SEM analysis. Cuticular wax was preserved only in air dried samples. Samples treated with chemical substances during the fixation and dehydration phases showed various alterations of the wax structures. In some air dried samples a loss of turgidity of the cells was observed that caused general wrinkling of the epidermal surfaces. Commercial FineFIX is an adequate substitute for formalin in histology and it can be applied successfully also for SEM investigation, while reducing the health risks of glutaraldehyde or other toxic fixatives. To investigate the potential for plants to absorb and capture particulates in air, which requires preservation of the natural morphology of trichomes and epicuticular waxes, a combination of FineFIX fixation and air drying is recommended.

Micropropagation of Homalomena pineodora Sulaiman & Boyce (Araceae): a new species from Malaysia

Homalomena pineodora (family Araceae) is a species found to have impressive foliage characteristics which remain evergreen throughout the year. Therefore, H. pineodora can be grown as an ornamental plant. Generally H. pineodora needs 3-5 years to propagate and multiply. However, the demand for new ornamental plants is increasing worldwide and the quality of planting material is a basic need for boosting productivity. Therefore an efficient micropropagation protocol for large-scale production of H. pineodora was developed. In vitro shoot cultures were initiated from the rhizomatous buds on MS basal medium. The best conditions for propagating H. pineodora was found to be MS medium supplemented with 3% sucrose and 0.5 mg L-1 BA (6-benzyladenine) under 24 h of cool fluorescent light which produced an average of 3.8 shoot per explant. Presence of an auxin was not necessary for plantlet production. Liquid MS medium supplemented with 0.5 mg L-1 BA, enhanced the shoot production of H. pineodora as compared to agar-gelled medium with same composition. All the in vitro plantlets of H. pineodora were successfully acclimatized with 100% survival rate. Scanning electron microscopy confirmed the similarity of leaf microstructures between the in vitro and mother plants of H. pineodora.

Primary investigations on the photosynthesis and respiration of leaves of Sargassum thunbergii using liquid-phase oxygen measurement system

For clarifying the physiological and ecological adaptability of leaves of Sargassum thunbergii,the photosynthesis and respiration were investigated by using liquid-phase oxygen measurement system.The major results included two aspects:(1) The differences of maximal net photosynthetic rate(Pnmax),saturation irradiance(Isat),light compensation point(Ic),initial quantum yield α,dark respiration rate(Rd),pigment content,specific leaf area and microstructure of heteromorphism leaf(broad leaf,narrow leaf,pneumathode) were analyzed to reveal the probable reason about the change of leaf shape of S.thunbergii.(2) Effects of different temperatures and different salinities stress on Pn and Rd of broad leaves of newborn branch of S.thunbergii were researched.The preliminary analysis of the newborn branch about resistance physiology could provide reference for the artificial cultivation of S.thunbergii based on vegetative reproduction.The results are shown as follows: The optimum temperature for growth of newborn branch is 15-24 ℃ under the experimental conditions in this paper.Pn had significant reduction when temperature was 5 ℃ or higher than 30 ℃ and Rd was significantly affected by low temperature(10 ℃ or below) or high temperature(higher than 30 ℃) stress for one hour treatment.However,Pn or Rd of low temperature stress groups could nearly recover to normal level after 24 h under standard culture condition.Short-term high or low salinity tests,especially salinity 0 and salinity 60 stress,had significant influence on Pn of broad leaves.However,Pn of salinity 0 group could recover to normal level after a 24 h recovery period,but Pn could not recover after exposure to salinity 60 for 9 h.During the whole stress process,Rd of salinity 40 and salinity 50 treatments both showed high values.And salinity 0 and salinity 60 stress both had significant influence on Rd.However,Rd could recover to normal level after a 24 h recovery period after exposure to different salinities for 9 h.

Effect of perforations of culture vessel cap on growth and leaf microstructure of in vitro plantlets of Artemisia annua L.

Glandular trichomes on leaf epidermis of Artemisia annua was a major site for artemisinin production. The influence of culture vessel fitted with or replaced with perforated cap was investigated on growth and microstructures of in vitro A. annua leaves. Increment in height and fresh biomass of plantlets regardless of clones (TC1, TC2 and Highland) in culture vessel fitted with normal cap were significantly higher than those cultures with perforated cap after eight weeks of culture. Desiccation of the culture medium was observed in culture vessels fitted with or replaced with perforated caps. Three clones showed different growth profile and sensitivity toward ventilation. T-shaped trichome (non-glandular) and capitates trichome (glandular trichome) were found on adaxial and abaxial epidermis of A. annua leaves. Using perforated cap induced more trichomes on the adaxial surface of leaf for all three tested clones. Stomata of plantlets cultured in culture vessels with normal caps were always opened and opposite trend observed in culture vessels replaced with perforated caps. Results indicated that ventilation due to cap type influenced the growth of in vitro plantlets and microstructures of A. annua leaves.