Adaxial Epidermis Research Articles

Anatomical parameters of the flag leaf of alloplasmic lines and their parental forms in drought conditions

Anatomical parameters of the flag leaf as criteria for drought tolerance of two alloplasmic lines (interspecific hybrids) and their parental forms − T. aestivum L. (cultivar of Mironovskaya-808) and T. dicoccum wheat were presented. The parameters studied were the thickness of the abaxial and adaxial epidermis, the thickness of the mesophyll and central vein, and the diameter of the central conducting bundle of the flag leaf. Different degrees of negative impact of sudden drought-stress and permanent water deficit on the anatomical structure of the flag leaf were shown. At the stage of flag leaf formation, anatomical parameters, for example an increase or preservation of the size of the protective and mechanical leaf tissues and the thickness of the mesophyll under stress can serve as criteria for the selection of drought-resistant forms of wheat. It revealed that among the studied genetic lineages the alloline D-d-05 showed the best adaptability and the most stable anatomical parameters of the flag leaf under conditions of moisture deficiency. The different degrees of drought tolerance of the studied lines indicate that the combination of the nucleus and cytoplasm of the parental forms can contribute to both an increase and a decrease in the level of drought tolerance in interspecific hybrids, which indicates the need to continue research with additional molecular genetic analysis. Key words: wheat, allolines, flag-list, anatomy, drought tolerance.

Polygalacturonase45 cleaves pectin and links cell proliferation and morphogenesis to leaf curvature in Arabidopsis thaliana.

Regulating plant architecture is a major goal in current breeding programs. Previous studies have increased our understanding of the genetic regulation of plant architecture, but it is also essential to understand how organ morphology is controlled at the cellular level. In the cell wall, pectin modification and degradation are required for organ morphogenesis, and these processes involve a series of pectin-modifying enzymes. Polygalacturonases (PGs) are a major group of pectin-hydrolyzing enzymes that cleave pectin backbones and release oligogalacturonides (OGs). PG genes function in cell expansion and separation, and contribute to organ expansion, separation and dehiscence in plants. However, whether and how they influence other cellular processes and organ morphogenesis are poorly understood. Here, we characterized the functions of Arabidopsis PG45 (PG45) in organ morphogenesis using genetic, developmental, cell biological and biochemical analyses. A heterologously expressed portion of PG45 cleaves pectic homogalacturonan in vitro, indicating that PG45 is a bona fide PG. PG45 functions in leaf and flower structure, branch formation and organ growth. Undulation in pg45 knockout and PG45 overexpression leaves is accompanied by impaired adaxial-abaxial polarity, and loss of PG45 shortens the duration of cell proliferation in the adaxial epidermis of developing leaves. Abnormal leaf curvature is coupled with altered pectin metabolism and autogenous OG profiles in pg45 knockout and PG45 overexpression leaves. Together, these results highlight a previously underappreciated function for PGs in determining tissue polarity and regulating cell proliferation, and imply the existence of OG-based signaling pathways that modulate plant development.

Floral Longevity of Paphiopedilum and Cypripedium Is Associated With Floral Morphology.

Floral longevity (FL) is an important trait influencing plant reproductive success by affecting the chance of insect pollination. However, it is still unclear which factors affect FL, and whether FL is evolutionarily associated with structural traits. Since construction costs and water loss by transpiration play a role in leaf longevity, we speculated that floral structures may affect the maintenance and loss of water in flowers and, therefore, FL. Here, we investigated the slipper orchid Paphiopedilum and Cypripedium, which are closely related, but strongly differ in their FL. To understand the evolutionary association of floral anatomical traits with FL, we used a phylogenetic independent comparative method to examine the relationships between 30 floral anatomical traits and FL in 18 species of Paphiopedilum and Cypripedium. Compared with Paphiopedilum species, Cypripedium species have lower values for floral traits related to drought tolerance and water retention capacity. Long FL was basically accompanied by the thicker epidermal and endodermal tissues of the floral stem, the thicker adaxial and abaxial epidermis of the flower, and low floral vein and stomatal densities. Vein density of the dorsal sepals and synsepals was negatively correlated with stomatal density. Our results supported the hypothesis that there was a correlation between FL and floral anatomical traits in slipper orchids. The ability to retain water in the flowers was associated with FL. These findings provide a new insight into the evolutionary association of floral traits with transpirational water loss for orchids under natural selection.

Leaf physiological and anatomical responses of two sympatric Paphiopedilum species to temperature

Paphiopedilum dianthum and P. micranthum are two endangered orchid species, with high ornamental and conservation values. They are sympatric species, but their leaf anatomical traits and flowering period have significant differences. However, it is unclear whether the differences in leaf structure of the two species will affect their adaptabilities to temperature. Here, we investigated the leaf photosynthetic, anatomical, and flowering traits of these two species at three sites with different temperatures (Kunming, 16.7 ± 0.2 °C; Puer, 17.7 ± 0.2 °C; Menglun, 23.3 ± 0.2 °C) in southwest China. Compared with those at Puer and Kunming, the values of light-saturated photosynthetic rate (Pmax), stomatal conductance (gs), leaf thickness (LT), and stomatal density (SD) in both species were lower at Menglun. The values of Pmax, gs, LT, adaxial cuticle thickness (CTad) and SD in P. dianthum were higher than those of P. micranthum at the three sites. Compared with P. dianthum, there were no flowering plants of P. micranthum at Menglun. These results indicated that both species were less resistance to high temperature, and P. dianthum had a stronger adaptability to high-temperature than P. micranthum. Our findings can provide valuable information for the conservation and cultivation of Paphiopedilum species.

Spatial patterning of scent in petunia corolla is discriminated by bees and involves the ABCG1 transporter.

Floral guides are patterned cues that direct the pollinator to the plant reproductive organs. The spatial distribution of showy visual and olfactory traits allows efficient plant-pollinator interactions. Data on the mechanisms underlying floral volatile patterns or their interactions with pollinators are lacking. Here we characterize the spatial emission patterns of volatiles from the corolla of the model plant Petunia×hybrida and reveal the ability of honeybees to distinguish these patterns. Along the adaxial epidermis, in correlation with cell density, the petal base adjacent to reproductive organs emitted significantly higher levels of volatiles than the distal petal rim. Volatile emission could also be differentiated between the two epidermal surfaces: emission from the adaxial side was significantly higher than that from the abaxial side. Similar emission patterns were also observed in other petunias, Dianthus caryophyllus (carnation) and Argyranthemum frutescens (Marguerite daisy). Analyses of transcripts involved in volatile production/emission revealed lower levels of the plasma-membrane transporter ABCG1 in the abaxial versus adaxial epidermis. Transient overexpression of ABCG1 enhanced emission from the abaxial epidermis to the level of the adaxial epidermis, suggesting its involvement in spatial emission patterns in the epidermal layers. Proboscis extension response experiments showed that differences in emission levels along the adaxial epidermis, that is, petal base versus rim, detected by GC-MS are also discernible by honeybees.

Comparative chemotaxonomic investigations on amaranthus hybridus l. and Amaranthus spinosus L.

The present study is set to investigate the comparative chemotaxonomic investigations on Amaranthus hybridus L. and Amaranthus spinosus L. which belong to the family Amaranthaceae. They are dicots pre-dominantly found in the Niger Delta Tropics, Nigeria. The species are annual erect herbs with flower inflorescences as elongated spikes which are mostly paniculate occurring at ends of branches in globose fashion in axils of leaves.The nodes often have pair of axillary spines. Flowers are small, greenish with male ones at the top while the female ones below the clusters and stem is greenish but often reddish with one-seeded capsule as fruit in Amaranthus spinosus which attains up to 80 ± 20cm in height whereas A. hybridus differ in absence of a pair of axillary spines, the stems are greenish or slightly pinkish which grows up to 100 ± 10cm in height. A. hybridus is more of a vegetable and has alternate phyllotaxi and narrow cuneate base. Fruits from both species are circumscissile capsules and their inflorescences are terminal racemes positioned at their axils with female perianth segments of five. Epidermal studies revealed amphistomatic stomata which is anisocytic type for both species. The stomatal index for A. spinosus adaxial foliar epidermis is 20% and the abaxial 20% whereas for A. hybridus adaxial is 20% and abaxial foliar stomatal index of 20%. Anatomical studies revealed open vascular system, collenchyma dominating the hypodermis while parenchyma occupied the general cortex and pith regions. A. hybridus has more vascular bundles and trichomes, and wider pith than A. spinosus. Phytochemical studies showed the presence of tannins, saponins, alkaloids, and flavonoids are present in A. spinosus while alkaloids were absent only in A. hybridus. This may be the reason why A. spinosus is used more in tradomedicine than A.hybridus which served more as vegetable.
 Key Words: Morphology, Anatomy, Phytochemistry, Amaranthus, Amaranthaceae

Mesofossils with noeggerathialean affinity based on epidermal characteristics from the Mississippian (lower Carboniferous) of Gansu Province, northwestern China

Three types of charcoalified mesofossils with anatomical structures are described from the Serpkhovian (Carboniferous) Jingyuan Formation in northwestern China. They are characterized by fragmental pinnules with apical teeth, dentate lateral margins, and simple stomatal apparati. Epidermal cells on both adaxial and abaxial surfaces are elongated trapezoidal with straight to slightly curved anticlinal walls. The first type has fan-shaped venation with veins extending into each apical tooth individually. Pinnules are amphistomatic. Stomatal apparati are rare on the adaxial surface, distributing sporadically on the apical part. On the abaxial surface, stomatal apparati are densely distributed in intercostal areas. Stomatal pores are oriented parallel to the veins. The second type is featured by the hypostomatic epidermis. Both adaxial and abaxial epidermis are not differentiated. The third type contains epidermis with clearly differentiated costal and intercostal areas. Adaxial and abaxial surfaces are similar in cell morphology and distribution. Pinnules are amphistomatic. Stomatal apparati are constrained within intercostal areas and are denser on the abaxial surface. Dome-shaped papillae are present on periclinal walls of cells in costal areas. These mesofossils are proposed to be of noeggerathialean affinity based both on the gross morphology and epidermal features. It is hypothesized that they represent three different taxa due to their distinct epidermal characteristics. In combination with macrofossil records from the same fossil interval, it confirms that noeggerathialeans were important components of Mississippian floras in China. The mesofossils reveal a probably higher diversity of this plant group than previously documented based only on macrofossils.

Biomass and Leaf Acclimations to Ultraviolet Solar Radiation in Juvenile Plants of Coffea arabica and C. canephora.

Despite the negative impacts of increased ultraviolet radiation intensity on plants, these organisms continue to grow and produce under the increased environmental UV levels. We hypothesized that ambient UV intensity can generate acclimations in plant growth, leaf morphology, and photochemical functioning in modern genotypes of Coffea arabica and C. canephora. Coffee plants were cultivated for ca. six months in a mini greenhouse under either near ambient (UVam) or reduced (UVre) ultraviolet regimes. At the plant scale, C. canephora was substantially more impacted by UVam when compared to C. arabica, investing more carbon in all juvenile plant components than under UVre. When subjected to UVam, both species showed anatomic adjustments at the leaf scale, such as increases in stomatal density in C. canephora, at the abaxial and adaxial cuticles in both species, and abaxial epidermal thickening in C. arabica, although without apparent impact on the thickness of palisade and spongy parenchyma. Surprisingly, C. arabica showed more efficient energy dissipation mechanism under UVam than C. canephora. UVam promoted elevated protective carotenoid content and a greater use of energy through photochemistry in both species, as reflected in the photochemical quenching increases. This was associated with an altered chlorophyll a/b ratio (significantly only in C. arabica) that likely promoted a greater capability to light energy capture. Therefore, UV levels promoted different modifications between the two Coffea sp. regarding plant biomass production and leaf morphology, including a few photochemical differences between species, suggesting that modifications at plant and leaf scale acted as an acclimation response to actual UV intensity.

ZmSPL10/14/26 are required for epidermal hair cell fate specification on maize leaf.

The epidermal hair and stomata are two types of specialized structures on the surface of plant leaves. On mature maize leaves, stomatal complexes and three types of hairs are distributed in a stereotyped pattern on the adaxial epidermis. However, the spatiotemporal relationship between epidermal hair and stomata development and the regulatory mechanisms governing their formation in maize remain largely unknown. Here, we report that three homologous ZmSPL transcription factors, ZmSPL10, ZmSPL14 and ZmSPL26, act in concert to promote epidermal hair fate on maize leaf. Cytological analyses revealed that Zmspl10/14/26 triple mutants are completely glabrous, but possess ectopic stomatal files. Strikingly, the precursor cells for prickle and bicellular hairs are transdifferentiated into ectopic stomatal complexes in the Zmspl10/14/26 mutants. Molecular analyses demonstrated that ZmSPL10/14/26 bind directly to the promoter of a WUSCHEL-related homeobox gene, ZmWOX3A, and upregulate its expression in the hair precursor cells. Moreover, several auxin-related genes are downregulated in the Zmspl10/14/26 triple mutants. Our results suggest that ZmSPL10/14/26 play a key role in promoting epidermal hair fate on maize leaves, possibly through regulating ZmWOX3A and auxin-related gene expression, and that the fates of epidermal hairs and stomata are switchable.

LEAF ANATOMY AND MICROMORPHOLOGY OF SELECTED EUPHORBIACEAE SPECIES IN KUANTAN, PAHANG, MALAYSIA

Leaf anatomy and micromorphology study was carried out on three selected taxa in Euphorbiaceae. The three chosen taxa were Jatropha curcas Linn., Euphorbia milii Des Moul. and Euphorbia hirta Linn. The methods involved procedures such as sectioning using sliding microtome, epidermal peeling and leaf micromorphology method using scanning electron microscope (SEM). The aim of this study is to identify the common, variation and diagnostic characteristics of leaf anatomy and micromorphology of selected species collected from Kuantan area which can give additional information for identification and classification of species. Findings in this study have shown that there were two common characters present in all the species studied which include the presence of mucilage cells and cuticular sculpturing of abaxial and adaxial epidermis. Meanwhile, several variable characters have been recorded in this study which can be useful in species differentiation such as vascular bundles arrangement in the midrib, pattern of anticlinal wall, types of stomata, waxes and trichomes. The diagnostic characteristics identified in this study are sinuous anticlinal wall pattern and anomocytic type of stomata that can only be found in E.hirta while crust of wax type and absence of trichomes can only be found in E.milii. The study reveals that leaf anatomy and micromorphology characteristics have taxonomic values and can be used as an additional data for identification and classification of species in Euphorbiaceae.

How cells and tissues of Daphnopsis fasciculata (Thymelaeaceae) react to the leaf-mining habit of Phyllocnistis hemera (Lepidoptera: Gracillariidae).

Plant cell and tissue responses to the attack of mining herbivores may be diagnosed by anatomical and histochemical analyses, herein investigated regarding the mining activity of Phyllocnistis hemera larvae in the leaf lamina of Daphnopsis fasciculata. The larva enters the leaf lamina through the adaxial epidermis, and feeds on palisade parenchyma cells. A healing tissue is produced after the larva passes, and its cells are reactive to histochemical tests for lignins and pectins. At first, the leaf mine is composed of a channel that is limited by palisade parenchyma cell wall fragments. Later, it is filled with a regenerative tissue constituted by isodiametric cells recruited from the spongy parenchyma, which fills up the mine channel. The cells differentiated inside the mine, regenerated the damage caused to leaf tissues, and may isolate the mine from the entrance of pathogens. Daphnopsis fasciculata is capable of reconstructing mesophyll tissues, which involves the totipotency of parenchyma cells and enables an important strategy for plant recovering after the attack of mining parasites.

Flavonoids in psidium guajava L. leaves

Theleaveshavebeen extensively investigated in the biology activity in human and animal health, where important metabolites such as phenols have been associated, of which the following stand out: flavonoids, tannins among other compounds, however this document aims to locate the anatomical location and analyze the content of major flavonoids in the mature and immature guava leaf. The study was complemented with the analysis of the ethyl ether and butanol extracts; The two types of leaves with their respective extracts were analyzed by thin layer chromatography, which allowed them to be detected and their concentration estimated by liquid chromatography. The study indicated that the mature leaf shows a large amount of flavonoids located in the adaxial and abaxial epidermis, as well as in glands, while in the immature leaf in the adaxial epidermis and in the abaxial epidermis it only presented a minimal proportion of them. Conclusion: Total flavonoid concentrations range from 2610 mg *kg-1 in the mature leaf to 2016 mg* kg-1 for the immature leaf, quercetin being the one that was found and observed in the highest proportion in both leaves.

MORPHOPHYSIOLOGICAL CHARACTERISTICS OF ARABIC COFFEE

The understanding of the behavior of each cultivar under adverse climatic conditions is important in the choice of plants that best fit the region to be inserted. Due to the large number of cultivars available on the market it makes it difficult for producers to choose which material to plant. In view of the above, this study aimed to know the morphophysiological characteristics of coffee. The experimental design was in randomized blocks with 10 treatments, that is, arabic coffee varieties: Catuai IAC62; Catuai IAC99; Ouro IAC4397; Tupi RN IAC1669-13; Obatã IAC1669-20; Mundo Novo IAC379-24; Mundo Novo IAC 388-17-2; Mundo Novo SH3 Faz São José; Bourbon IACJ15 and Icatu IAC 2944-11 and with four replications totaling 40 plots, where each plot was composed of seven plants. The Mundo Novo IAC 388-17-2 coffee variety shows higher yield in the seventh year of cultivation. Variety of Bourbon IACJ15 coffee presented water use efficiency (EUW) which did not reflect in higher productivity. The Catuai V IAC99 arabica coffee variety stood out in the internal morphology of the leaves. The thickness of the adaxial and abaxial epidermis (TADE and TABE) and the CO2 assimilation rate (A) showed negative correlations with the productivity of processed coffee bags. Keywords: Coffea arabica; plant morphology; plant physiology; varieties.

Toxic effects of cadmium on growth of Aloe ferox Mill

Heavy metals like cadmium (Cd) are a serious threat for living organisms due to increased global environmental pollution. Aloe ferox Mill. is a very important species of the genus Aloe, especially from a medical point of view, because it is a source of biologically active substances and it is often used in the traditional medicine. Since the knowledge about the effect of heavy metals, like Cd on growth of Aloe species is scarce, this study showed the effect of Cd on anatomical, morphological and physiological properties of this important medicinal plant species. We found that Cd affected the leaf morphology and decreased biomass of the aboveground plant part. Cd also affected cuticle deposition and increased the number of stomata in the abaxial and adaxial epidermis of leaves. Roots treated with Cd showed lower lignification and decreased level of membrane lipids peroxidation than control roots. Cadmium concentration was the highest in the roots; however, relatively high portion of Cd is being translocated to the leaves. This might be dangerous as Aloe is well known medicinal plant with content of active secondary metabolites mainly in the leaves.

A new endemic and critically endangered species of Butia (Arecaceae) with comments on morpho-anatomical novelties in the genus

Butia buenopolensis, a new dwarf Arecaceae species, is described. Butia buenopolensis occurs in the Serra do Cabral mountain range in Buenopolis municipatility, Minas Gerais, Brazil. Despite its diminutive size, it has arched yellowish-green leaves and pinnae not as narrow as the species of the grass-like Butia. The new species is closely related to B. archeri, based on morphology, phenology (flowering time) and habitat. They differ in leaf anatomy, plant size, color and size of inflorescence. Some novelties in Butia flower morphology, such as striated cuticle of anthers, functional staminodes presenting evidence of secretory activity, raphides on the petals of pistillate flowers and the cappilinection adhesion of petal margins, were introduced here and suggested as a new approach for future taxonomical and evolutionary studies of this genus. The isolated and small groups of fibers in the mesophyll and a non-vascular fiber bundle connected to the adaxial epidermis in the leaf midrib have not been found in any other Butia so far. The one population recorded for the new species is restricted to an area near the limits of Serra do Cabral State Park, clearly vulnerable to different forms of anthropic pressure. So, it is strongly recommended an extension in area of Serra do Cabral State Park to include the B. buenopolensis range of occurrence within its borders.

Relationship between the agronomic and anatomical characteristics of the leaf with a view to indirect selection in maize plants

ABSTRACT In crops such as maize, the leaf is directly related to dry-matter accumulation in the grain, and directly affects plant yield. The aim of this study was to verify the existence of a correlation between the agronomic and anatomical characteristics of the maize leaf, as well as to verify the effects of these characteristics on grain production using path analysis. The agronomic characteristics used in the analysis were plant height, height of ear insertion, relative position of the ear, lodging, plant breakage and grain yield. The following anatomical characteristics were evaluated: total leaf area, thickness of the bulliform cells, thickness of the adaxial and abaxial epidermis, thickness of the mesophyll, area of the xylem, phloem and sclerenchyma, and mean area of ​​the vascular bundles. In analysing the genotypic correlation, associations were seen at 1% significance between mesophyll thickness and plant height, mesophyll thickness and height of ear insertion, and mesophyll thickness and plant breakage, indicating the possibility of indirect selection for these agronomic characteristics. From the path analysis, it was found that the agronomic characteristics of lodging and breakage, and the anatomical characteristics of thickness of the adaxial epidermis, area of ​​the xylem and area of ​​the sclerenchyma had the greatest direct effect on grain yield, indicating the additional possibility of indirect selection for yield during the earliest stages of the plant. These results can afford faster selection of superior genotypes within the various breeding programs of the species.

Leaf morphoanatomical traits of Jacquinia armillaris Jacq. (Theophrastoideae - Primulaceae) in two xeric shrublands from Venezuela

ABSTRACT This study aimed to investigate the leaf anatomy of Jacquinia armillaris plants in two different Venezuelan xeric shrublands to evaluate possible variations caused by the environments, which differ in rainfall and soil salinity. Leaf samples were collected in two sites: La Tortuga Island, a dryer and salty environment than the other collecting site, Turpialito, a coastal location in the mainland. The epidermis and the mesophylls were observed with a light microscope and measured with an ocular micrometer inserted in one of the eyepieces. The results show that J. armillaris has many characteristic anatomical traits of xerophytes, among them: thick cuticles and thick epidermis in both leaf surfaces, stomata only in the abaxial side and epidermal depressions lodging a glandular trichome. Leaves are bifacial and present multistratified palisade parenchyma facing the adaxial epidermis and abaxial spongy parenchyma with abundant intercellular spaces. Furthermore, the hypodermis is composed of one or two cell layers below the upper epidermis. Leaf lamina dimension, petiole, cuticles, epidermis and hypodermis cells, as well as the stomatal occlusive cells and number of trichomes, had differences in size and number when the plants of both sites were compared, being higher in plants from La Tortuga. On the other hand, palisade parenchyma and stomatal density were higher in Turpialito plants. Plants collected in La Tortuga Island showed characteristics that suggest adaptation to the island’s saline and more arid conditions in comparison to plants from Turpialito, which presented more leaf traits related to adaptations to water deficit. These results demonstrate the phenotypic plasticity of J. armillaris plants that grow in two different xeric shrublands.

Fossil seed fern Lepidopteris ottonis from Sweden records increasing CO2 concentration during the end-Triassic extinction event

The end-Triassic event (ETE), a short global interval occurring at the end of the Triassic Period (~201.5 Ma), was characterized by climate change, environmental upheaval, as well as widespread extinctions in both the marine and terrestrial realms. It was associated with extensive perturbations of the carbon cycle, principally caused by the volcanic emplacement of the Central Atlantic Magmatic Province in relation to the break-up of Pangea. The correlated change in atmospheric CO2 concentrations (pCO2) can be reconstructed with the stomatal proxy, which utilizes the inverse relationship between stomatal densities of plant leaves (here stomatal index (SI), which is the percentage of stomata relative to epidermal cells) and pCO2. Fossilized Lepidopteris leaves are common and widespread in Triassic strata, thus offering great potential for high-resolution pCO2 reconstructions. A dataset of leaf cuticle specimens belonging to the seed fern species Lepidopteris ottonis from sedimentary successions in Skåne (Scania), southern Sweden, provided the possibility of pCO2 reconstruction at the onset of the ETE. Here, we tested the intra- and interleaf variability of L. ottonis SI, and estimated the pCO2 during the onset of the ETE. Our findings confirm L. ottonis as a valid proxy for palaeo-pCO2, also when using smaller leaf fragments. Importantly, the statistical analyses showed that the SI values of abaxial and adaxial cuticles are significantly different, providing a tool to distinguish between the two sides and select cuticles for analysis. Reconstructed pCO2 increased from ~1000 pre ETE to ~1300 ppm at the onset of the event, a significant increase of ~30% over a relatively short time period. The pCO2 recorded here is similar to previously published estimates, and strongly supports the observed pattern of elevated pCO2 at the onset of the ETE.

Effects of Pressure Reduction Modes on Vacuum Cooling Efficiency and Quality Related Attributes of Different Parts of Pakchoi (Brassica Chinensis L.)

Abstract Rapid/moderate/slow pressure reduction modes of vacuum cooling (VC) with pressure reduction rates ranging from 0.0043 to 0.0502 s-1 were developed. The effects of VC in different modes on the cooling efficiency and quality-related attributes of different edible parts of pakchoi including total and free water contents, colour differences, respiration rates, membrane stability and microstructures were investigated, and the cluster analysis (CA) was employed for visualizing and classifying the VC-induced quality variation. Results showed that the leaf and the petiole exhibited different temperature changes and vacuum tolerances, of which the adaxial epidermis of the leaf was more sensitive to VC, showing more severe cell damage due to the internal moisture gradient. The rapid pressure reduction mode (α1 = 0.0502 s-1) could predominately improve cooling efficiency and minimize the quality attenuation, while the moderate pressure reduction mode (α2 = 0.0184 s-1) contributed to better temperature uniformity and colour acceptance. Moreover, the result of CA further confirmed the above conclusions, suggesting that α1 and α2 endowed pakchoi with similar quality-related attributes to the fresh one. The current study proved that the slow pressure reduction mode should be avoided for uses in VC of leafy vegetables.

Substrate composition affects the development of water stress and subsequent recovery by inducing physiological changes in Cistus albidus plants

Organic residues (compost) can be used as growth medium but may contain phytotoxic ions that, combined with a water deficit may alter the behavior of plants. The experiment was carried out in a growth chamber with Cistus albidus in a commercial substrate, C (sphagnum peat, coconut fiber and perlite, 8:7:1) and a mixture of compost substrates, Cp (slurry compost, coconut fiber and perlite, 3:6:1). Plants were grown in pots under well-watered, maintaining values of Ψl around −0.9 MPa (WW) and water-stressed (WS) conditions, where the irrigation was removed until reached values of Ψl around −3.0 MPa (water stress period), after then, water was re-established in all plants (recovery period). Although, the well-watered plants had a leaf water potential (Ψl) around −0.9 MPa, stomatal conductance (gs) was 125 mmol m−2s−1 in the commercial substrate and 30 mmol m−2s-1 in compost. The time taken to reach the threshold value at which water stress occurs was 13 days in the commercial substrate and 53 days in compost. Water-stressed plants in the commercial substrate had significantly lower values of Ψl and gs than well-watered. Plants in compost maintained values of gs similar in both irrigation treatments (WW and WS) and accumulated less biomass than those that grown in commercial. The water stress in compost led an increase in the adaxial epidermis, parenchyma and mesophyll, whereas water stress in commercial the proportions of the different tissues decreased. Higher lipid peroxidation values were found in plants grown in both substrates under water stress. The recovery time of the plants, until manage Ψl values around −0.9 MPa, depended on the type of substrate. The restoration of irrigation in commercial substrate act as a new stress, as reflected in the photochemical mechanisms.