To improve large-scale in vitro production of Oplopanax elatus Nakai, we cultured somatic embryo-derived plantlets under a heterotrophic condition (semi-solid culture with sucrose), photoautotrophic condition (semi-solid culture without sucrose), or modified photoautotrophic condition (liquid culture with forced ventilation). The plantlets grown under the modified photoautotrophic condition had more leaves as well as higher chlorophyll content, and higher net photosynthetic rate than those grown under the conventional conditions. Further, the photoautotrophically grown plantlets acclimatized better and sooner upon ex vitro transplantation than did the conventionally cultured plantlets. Consequently, a photoautotrophic culture method with forced ventilation is effective for enhancing the growth and acclimatization of O. elatus.

Although crosstalk between cytosolic and plastidic terpenoid pathways has been validated in many plant species, we report here for the first time a striking elevation of the nucleus-encoded artemisinin biosynthesis relevant DBR2 mRNA following the incubation of plants with fosmidomycin (FM). FM decreased singlet oxygen (¹O₂) scavengers such as β-carotene and α-tocopherol and subsequently invoked ¹O₂ burst. The treatment of plants with fluridone (FD) neither decreased α-tocopherol content nor triggered ¹O₂ emission. In conclusion, FM can up-regulate ¹O₂-sensitive nuclear genes responsible for artemisinin biogenesis by mitigating the accumulation of plastidic scavenging terpenoids, thereby eliciting ¹O₂ generation and initiating ¹O₂ retrograde signaling.

Application of gibberellic acid (GA₃) on the cotyledons of 5-d-old Pharbitis nil reversed the inhibitory effect of both abscisic acid (ABA) and ethylene on flowering. Application of GA₃ slightly decreased ethylene production and did not affect the endogenous ABA content in the cotyledons during the night. However, it reversed the stimulating effect of ABA on ethylene production.

The aim of this study was to investigate acclimation of micropropagated plants of Rhododendron ponticum subsp. baeticum to different irradiances and recovery after exposure to high irradiance. Plants grown under high (HL) or intermediate (IL) irradiances displayed higher values of maximum electron transport rate (ETR_max) and light saturation coefficient (E_k) than plants grown under low irradiance (LL). The capacity of tolerance to photoinhibition (as assessed by the response of photochemical quenching, q_p) varied as follows: HL > IL > LL. Thermal energy dissipation (q_N) was also affected by growth irradiance, with higher saturating values being observed in HL plants. Light-response curves suggested a gradual replacement of q_p by q_N with increasing irradiance. Following exposure to irradiance higher than 1500 μmol m^-2 s^-1, a prolonged reduction of the maximal photochemical efficiency of PS 2 (F_v/F_m) was observed in LL plants, indicating the occurrence of chronic photoinhibition. In contrary, the decrease in F_v/F_m was quickly reverted in HL plants, pointing to a reversible photoinhibition.

The influence of combined and individually applied drought and heat stress was studied in two wheat (Triticum aestivum L.) cultivars: resistant cv. Katya and susceptible cv. Sadovo. Relative water content decreased and electrolyte leakage increased due to individual and combined application of both stresses. Initial heat shock protein profile has been outlined via SDS electrophoresis of leaf extracts. The results obtained were confirmed by immunoblotting with anti-HSP70 monoclonal antibodies, anti-HSP110 polyclonal antibodies and anti-α β-crystalline polyclonal antibodies. The effect of simultaneously applied water stress and heat shock resembled the alterations in protein expression provoked only by water stress and differed significantly from the changes occurring after the individual application of heat stress.

Plants have capability to optimize its architecture by using CDK pathways. It involves diverse types of cyclin dependent kinase enzymes (CDKs). CDKs are classified in to eight classes (CDKA to CDKG and CKL) based on the recognized cyclin-binding domains. These enzymes require specific cyclin proteins to get activated. They form complex with cyclin subunits and phosphorylate key target proteins. Phosphorylation of these target proteins is essential to drive cell cycle further from one phase to another phase. During cell division, the activity of cyclin dependent kinase is controlled by CDK interactor/inhibitor of CDKs (ICK) and Kip-related proteins (KRPs). They bind with specific CDK/cyclin complex and help in controlling CDKs activity. Since cell cycle can be progressed further only by synthesis and destruction of cyclins, they are quickly degraded using ubiquitination-proteasome pathway. Ubiquitylation reaction is followed by DNA duplication and cell division process. These two processes are regulated by two complexes known as Skp1/cullin/F-box (SCF)-related complex and the anaphase-promoting complex/cyclosome (APC/C). SCF allows cell to enter from G1 to S phase and APC/C allows cell to enter from G2 to M phase. When all these above processes of cell division are going on, genes of cyclin dependent kinases gets activated one by one simultaneously and help in regulation of CDK pathways. How cell cycle is regulated by CDKs is discussed.

Mechanisms of drought tolerance have been studied by numerous groups, and a broad range of molecules have been identified to play important roles. A noteworthy response of stressed plants is the accumulation of novel protective proteins, including heat-shock proteins (HSPs) and late embryogenesis abundant (LEA) proteins. Identification of gene regulatory networks of these protective proteins in plants will allow a wide application of biotechnology for enhancement of drought tolerance and adaptation. Similarly, aquaporins are involved in the regulation of water transport, particularly under abiotic stresses. The molecular and functional characterization of protective proteins and aquaporins has revealed the significance of their regulation in response to abiotic stresses. Herein, we highlight new findings regarding the action mechanisms of these proteins. Finally, this review also surveys the current advances in engineering drought tolerant plants, particularly the engineering of protective proteins (sHSPs and LEA) and aquaporins for imparting drought stress tolerance in plants.

Mature seed-derived embryogenic calli of indica rice (Oryza sativa L. cv. PAU201) were induced on semisolid Murashige and Skoog medium supplemented with 2.5 mg dm^-3 2,4-dichlorophenoxyacetic acid + 0.5 mg dm^-3 kinetin + 560 mg dm^-3 proline + 30 g dm^-3 sucrose + 8 g dm^-3 agar. Using OsglyII gene, out of 3180 calli bombarded, 32 plants were regenerated on medium containing hygromycin (30 mg dm^-3). Histochemical GUS assay of the hygromycin selected calli revealed GUS expression in 50 % calli. Among the regenerants, 46.87 % were GUS positive. PCR analysis confirmed the presence of the transgene of 1 kb in 60 % of independent plants. Further, these plants have been grown to maturity in glasshouse. In vitro screening for salt tolerance showed increase in fresh mass of OsglyII putative transgenic calli (185.4 mg) as compared to control calli (84.2 mg) on 90 mM NaCl after 15 d. When exposed to 150 mM NaCl, OsglyII putative transgenic plantlets showed normal growth while the non-transgenic control plantlets turned yellow and finally did not survive.

Induction of somatic embryogenesis in leaf explants from young mangosteen seedlings using different concentrations and combinations of 6-benzylaminopurine (BAP) and thidiazuron (TDZ) was investigated. The best medium inducing the formation of globular structures (40 %) was Murashige and Skoog medium with 0.7 mg dm^-3 BAP and 0.7 mg dm^-3 TDZ. For their further development, subculturing onto different maturation media was carried out, but these globular structures did not develop futher stages of somatic embryogenesis. However, they developed shoots after 90 d of culture on the original medium. Morphological and histological analyses were performed, and showed that the globular structures resembled closely the undifferentiated structure of the mangosteen seed. We propose that the development of mangosteen somatic embryos does not follow the typical course of somatic embryogenesis, but the course of development that is natural for mangosteen seed, where procambium is the only structure observed and there is no differentiated embryo.

The effects of trehalose pretreatment on thylakoid membranes of winter wheat were investigated under heat stress. Under normal growth conditions, the winter wheat synthesized 502 μg g^-1(f.m.) trehalose, which increased to 1250 μg g^-1(f.m.) under heat stress and to 1658 μg g^-1(f.m.) in trehalose-pretreated seedlings. Under heat stress, proteins in the thylakoid membranes and the photosynthetic capacity were protected by trehalose pretreatment. Moreover, the electrolyte leakage, contents of malondialdehyde, superoxide anion and hydrogen peroxide, and lipoxygenase activity in trehalose-pretreated seedlings were lower than in the non-pretreated plants.

The possible costs of inducible defences against pests were evaluated in tomato. To activate inducible resistance traits, we used transgenic plants that over-expressed the systemin precursor (prosystemin). The constitutive expression of the prosystemin, which is normally induced by herbivores in tomato, allowed the measurement of the impact of induced defences in a pest-free environment. The results showed that the continuous activation of traits that are normally induced by pests should be costly, affecting the growth, physiology and reproductive success of tomato plants.

Rooted cuttings of Populus nigra L. clone Poli and Salix alba L. clone SS5 were treated for three weeks with 50 μM CdSO₄ in nutrient solution. The willow showed a far higher Cd tolerance, expressed as tolerance index (Ti), than the poplar in both roots and leaves. The root Cd content was higher in poplar than in willow, whereas in leaves the opposite was found. As a consequence, the translocation factor (Tf) revealed a greater ability of Cd transport in willow than in poplar. Cd treatment enhanced cysteine, γ-glutamylcysteine and reduced glutathione contents in roots of both species, whereas in leaves they were only enhanced in poplar. Furthermore, only poplar leaves showed an enhanced content of phytochelatins, whereas malic and citric acids rose in response to Cd only in the willow leaves. Cd treatment increased putrescine, spermidine and spermine contents in both roots and leaves of the willow, whereas in poplar only the putrescine content was enhanced in roots.

The changes in ultrastructure of leaf cell in waterlogged Kosteletzkya virginica seedlings were observed by transmission electron microscope. During waterlogging, the chloroplasts turned into a round shape and their volume was gradually reduced. Furthermore, the lamellae of thylakoids swelled, and the inclusions in chloroplast decreased. The shape of starch grains slightly changed, but their number and volume decreased, and they even disappeared in the end. On the other hand, plastoglobules enlarged and their amount enhanced gradually. The membrane and inner cristea of mitochondria gradually became unclear, while the mitochondria firstly enlarged but disappeared at the end. Similar to chloroplast, cell nucleus dwindled gradually, concentrated and tended to a round shape. Additionally, the annulate lamellae and multivesicular body occurred on the 20th day of experiment, and the cell wall distorted and twisted at the late stage of waterlogging. Consequently, these changes of organelles are the typical characteristics of the complete cell disintegration or death for Kosteletzkya virginica under long-term waterlogging.

Four new microsatellite primer pairs were developed in tree peony (Paeonia suffruticosa) based on the database mining and other twenty-six primer pairs by fast isolation by AFLP of sequences containing repeats (FIASCO) method. The polymorphism of each locus was further evaluated in 40 individuals of one population plus 5 tree peony related species. The number of alleles per locus ranged from 3 to 7 and the expected (H_e) and observed (H_o) heterozygosity at each locus ranged from 0.42 to 0.78 and 0.28 to 0.59, respectively. These microsatellite markers will be useful for investigating genetic diversity and studies of population genetic structure of tree peony.

Effects of reduced atmospheric pressure on morphogenic potential and antioxidative enzyme activities in regenerated tissues of Saussurea involucrata were evaluated. Leaf explants were cultured at atmospheric pressure 30, 60 or 101 kPa on Murashige and Skoog (MS) medium with several plant growth regulators (PGRs). Oxygen and carbon dioxide partial pressures were maintained at 21 and 0.038 kPa, respectively. At 60 kPa, 12 shoots per explant were recorded, which was 1.5 and 2.1-folds higher than at 101 and 30 kPa, respectively. A shooting frequency of 80 % was observed at 60 and 101 kPa. Rooted plantlets were obtained on MS medium with indoleacetic acid. At 30, 60 and 101 kPa, rooting of shoots was 49, 72 and 85.6 %, respectively. The rooted plantlets were successfully acclimatized to soil. Activities of all of antioxidative enzymes determined in present study were affected by hypobaric conditions.

We studied the nutritional modes of the orchid Serapias strictiflora and its mycorrhizal fungus Epulorhiza sp. using the differences in carbon isotopic composition (δ¹³C) of C₃ orchid and C₄ maize tissues. We found that if cultivated in substrate lacking any organic compounds, the mycorrhizal extraradical mycelia (δ¹³C = -26.3 ± 0.2 ‰) developed well, despite being fully dependent on nutrition from orchid roots (δ¹³C = -28.6 ± 0.1 ‰). If the mycorrhizal fungus had additional access to and colonized decaying maize roots (δ¹³C = -14.6 ± 0.1 ‰), its isotopic composition (δ¹³C = -21.6 ± 0.4 ‰) reflected a mixture of biotrophy and saprotrophy. No statistically significant differences in δ¹³C of new storage tubers were found between Epulorhiza-associated orchids with (δ¹³C = -28.2 ± 0.1 ‰) and without access to maize roots (δ¹³C = -28.6 ± 0.2 ‰). We conclude that autotrophy is the predominant nutritional mode of mature S. strictiflora plants and that they supply their mycorrhizal fungus with substantial amount of carbon (69 ± 3 % of the fungus demand), even if the fungus feeds saprotrophically.

The effect of maturation pretreatment on development and growth of Abies numidica De Lann. somatic embryos was studied. The most beneficial was pre-culturing on Schenk and Hildebrandt medium without growth regulator for 2 weeks. Dry mass accumulation of emblings was lower than that of seedlings after 50 d of culturing. Contents of microelements in seedlings were higher than in emblings, but macroelements contents were higher in emblings. Contents of chlorophyll a and chlorophyll b in cotyledons were higher in seedlings than in emblings while no qualitative differences were detected between the protein profiles of seedlings and emblings.

The responses of antioxidant enzymes (AOE) ascorbate peroxidase (APX), glutathione reductase (GR), superoxide dismutase (SOD), and catalase (CAT) in soluble protein extracts from leaves and roots of tobacco (Nicotiana tabacum L. cv. Samsun NN) plants to the drought stress, salinity and enhanced zinc concentration were investigated. The studied tobacco included wild-type (WT) and transgenic plants (AtCKX2) harbouring the cytokinin oxidase/dehydrogenase gene under control of 35S promoter from Arabidopsis thaliana (AtCKX2). The transgenic plants exhibited highly enhanced CKX activity and decreased contents of cytokinins and abscisic acid in both leaves and roots, altered phenotype, retarded growth, and postponed senescence onset. Under control conditions, the AtCKX2 plants exhibited noticeably higher activity of GR in leaves and APX and SOD in roots. CAT activity in leaves always decreased upon stresses in WT while increased in AtCKX2 plants. On the contrary, the SOD activity was enhanced in WT but declined in AtCKX2 leaves. In roots, the APX activity prevailingly increased in WT while mainly decreased in AtCKX2 in response to the stresses. Both WT and AtCKX2 leaves as well as roots exhibited elevated abscisic acid content and increased CKX activity under all stresses while endogenous CKs and IAA contents were not much affected by stress treatments in either WT or transgenic plants.

A two-step protocol for improving the frequency of shoot regeneration from oilseed rape (Brassica napus L.) hypocotyl explants was established. The protocol consists of a pre-culture on callus induction medium (CIM) and a subsequent shoot regeneration on shoot induction medium (SIM). The SIM was Murashige and Skoog medium supplemented with different concentrations of 6-benzylaminopurine (BA; 2-5 mg dm^-3) and naphthaleneacetic acid (NAA; 0.05-0.15 mg dm^-3). Maximum frequency of shoot regeneration (13 %) was on the SIM medium containing 4 mg dm^-3 BA and 0.1 mg dm^-3 NAA, but it increased to 24.45 % when 20 μM silver thiosulphate (STS) was added. Strikingly, an extremely high frequency of shoot regeneration up to 96.67 % was reached by a two-step protocol when hypocotyl explants had been pre-cultured for 7 d on a CIM medium containing 1.5 mg dm^-3 2,4-dichlorophenoxyacetic acid. In addition, the shoot emergence was also 7 d earlier than that observed by use of the one-step protocol. The two-step protocol was also applied for regeneration of transgenic plants with cZR-3, a nematode resistance candidate gene. As a result, 43 plants were generated from 270 shoots and from these 6 plants proved to be transgenic.

Programmed cell death (PCD) was induced by the Yariv reagent in Nicotiana tabacum cv. Bright Yellow-2 cell suspension. The analyses of proteins extracts by 2-D electrophoresis clearly show massive protein degradation which was mainly due to cysteine protease activity. In contrast, some proteins remained unchanged up to 72 h after PCD induction. Peptide mass fingerprints of these proteins, obtained by MALDI-TOF, identified calreticulin, heat shock protein (HSP) 60, HSP70, malate dehydrogenase and mitochondrial ATP synthase β-subunit.

Protein extracts, made to leaves harvested from the stolons of the pasture legume white clover (Trifolium repens L.) at two developmental stages (newly initiated; onset of senescence) were purified further using reverse-phase and ionexchange chromatography. Fractions enriched with the ethylene biosynthetic enzyme 1-aminocyclopropane-1-carboxylate (ACC) oxidase were selected for each stage and the final, partially purified fraction was subjected to twodimensional gel electrophoresis (2DE). Antibodies raised against a recombinant ACC oxidase (ACO) from white clover (antiTR-ACO2) recognised a series of spots of differing pI suggesting that ACO undergoes post-translational modifications. Further, the pattern differed between the ACO proteins partially purified from newly initiated leaves with leaves at the onset of senescence suggesting that the environmental and developmental cues that operate in each tissue influences the type and/or degree of post-translational modifications of the ACO protein. MALDI-TOF mass spectrometry was used to identify protein spots associated with the ACO proteins. Protein with identities to an ACO isoform from Oryza sativa, and a phosphoribulokinase from Arabidopsis thaliana were identified in the 2DE separations from newly initiated leaves, while an isoflavone reductase from Medicago sativa was identified in the 2DE separation of the senescent leaf extract.

Squalene synthase (SS) dimerizes two molecules of farnesyl diphosphate to synthesize squalene, a shared precursor in steroid and triterpenoid biosynthesis in plants. The SS1 gene encoding SS from Arabidopsis thaliana was introduced in Withania coagulans under the control of the CaMV35S promoter together with the T-DNA of Agrobacterium rhizogenes A4. The engineered hairy roots were studied for withanolide production and phytosterol accumulation and the results were compared with those obtained from control roots harbouring only the T-DNA from pRiA4. The increased capacity of the engineered roots for biosynthesizing phytosterols and withanolides was strongly related with the expression level of the transgene, showing the effectiveness of overexpressing 35SS1 to increase triterpenoid biosynthesis.

Seedlings of Camellia sinensis were grown hydroponically for 30 d in order to study the effect of fluorine (F) on growth parameters, antioxidant defence system, photosynthesis and leaf ultrastructure. Fresh and dry mass, chlorophyll (Chl) content and net photosynthetic rate (P_N) decreased with increasing F concentration. Superoxide dismutase (SOD) activity decreased significantly, catalase (CAT) and guaiacol peroxidase (GPX) activities reached maximun under 0.21 and 0.32 mM F, respectively. Proline, malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) contents increased significantly. These results suggested, that antioxidant defence system of leaves did not sufficiently scavenge excessive reactive oxygen species. The cell ultrastructure was not changed under 0.11-0.21 mM F, however, it was destroyed at 0.32-0.53 mM F. So tea plants tolerated F in concentration less than 0.32 mM.

The root system of potato (Solanum tuberosum L. cv. Favorita) plants was treated with different O₂ and CO₂ concentrations for 35 d in aeroponic culture. Under 21 or 5 % O₂ in the root zones, the thickness of leaves and palisade parenchyma significantly increased at 3 600 μmol(CO₂) mol^-1 in the root zone, compared with CO₂ concentration 380 μmol mol^-1 or low CO₂ concentration (100 μmol mol^-1). In addition, smaller cells of palisade tissue, more intercellular air spaces and partially two layers of palisade cells were observed in the leaves with root-zone CO₂ enrichment. Furthermore, there was a significant increase in the size of chloroplasts and starch grains, and the number of starch grains per chloroplast due to elevated CO₂ only under 21 % O₂. In addition, a significant decline in the thickness of grana and the number of lamellas, but no significant differences in the number of grana per chloroplast were observed under elevated CO₂ concentration. The accumulation of starch grains in the chloroplast under elevated CO₂ concentration could change the arrangement of grana thylakoids and consequently inhibited the absorption of sun radiation and photosynthesis of potato plants.

The use of expressed sequence tag-simple sequence repeat (EST-SSR) markers might reflect the better relationship among species or cultivars than markers previously used. The first set of 30 EST-SSR was developed in hop (Humulus lupulus L.). They represent 25 gene loci with total of 1268 EST sequences. They were used for characterization of 11 hop samples and cross-amplification in Humulus japonicus Sieb. et Zucc. The number of alleles per locus ranged from two to nine. The observed and expected heterozygosities ranged from 0.182 to 0.956 and from 0.233 to 0.775, respectively. We used EST-SSR markers for cluster analysis of hop genotypes. Dendrogram well matched with genealogical and geographical data for hop genotypes.

Xylanase inhibitor TAXI-I gene was cloned from wheat (Triticum aestivum L.) and then TAXI-I encoding sequence was expressed in Escherichia coli. The recombinant TAXI-I protein inhibited glycoside hydrolase (GH) family 11 xylanases in Aspergillus niger (Anx; a fungal xylanase), and Thermomonospora fusca (Tfx; a bacterial xylanase), and also inhibited hybrid xylanases Atx (a hybrid xylanase whose parents are T. fusca and A. niger) and Btx (a hybrid xylanase whose parents are T. fusca and Bacillus subtilis). Among the tested xylanases, A. niger xylanase was the most inhibited one by wheat xylanase inhibitor TAXI-I, while T. fusca xylanase was the least inhibited one. The profile of TAXI-I gene expression in wheat in response to phytohormones was also investigated. TAXI-I gene expression was drastically induced by methyl jasmonate (MeJa), and hardly detected in gibberellic acid (GA) treatment. Therefore, TAXI-I might be involved in plant defense against fungal and bacteria xylanases.

Short-time direct and indirect effects of 25 μM Cd on the growth of dicotyledon (Phaseolus coccineus) and monocotyledon (Allium cepa) plants were investigated in the presence of inhibitors of ethylene synthesis, NADPH oxidase, and the octadecanoid pathway. Only 5 min-long action of Cd was enough for inhibition of growth in bean roots, but its recovery time was extended to several days. After 7 h treatment, Cd was significantly accumulated in bean roots, but maximum H₂O₂ accumulation was seen after 1 h. Cd-induced H₂O₂ accumulation decreased especially after addition of ethylene inhibitor silver thiosulphate (STS). Low Cd accumulation and high growth inhibition were observed also in bean leaves and in A. cepa roots. The inhibitors of the octadecanoid pathway greatly weakened the inhibitory effect of Cd in P. coccineus roots, while no significant effect was observed in A. cepa. NADPH oxidase and ethylene blockade reversed (in the case of bean plants and indirectly treated A. cepa plants) or significantly diminished Cd action. Cd-induced growth inhibition of P. coccineus leaves was also alleviated by most inhibitors of the jasmonate pathway and by STS. These results indicate that Cd may have indirect and direct effects on growth processes.

In this study we identified and characterized a major latex lectin - designated as EtLLH - with antimicrobial activity from the succulent African milk tree Euphorbia trigona. The lectin is highly concentrated in the latex of E. trigona and appears to be composed of at least two subunits with a molecular mass of 32 kDa. EtLLH shares significant similarities to known plant lectins - ricin from Ricinus communis and agglutinin from Viscum album coloratum - which specifically bind D-galactose and N-acetyl-D-glucosamine, the major building blocks of many fungal cell walls. Antimicrobial activity assays revealed an impact of EtLLH on three phytopathogenic filamentous ascomycetes. The germination of the conidiospores and the hyphal growth of Aspergillus niger and Fusarium graminearum were severely inhibited by EtLLH already at concentrations below 0.1 mg cm^-3, while the effect on germination of the melanized conidiospores of Botrytis cinerea was less significant.

This study was carried out to investigate the in vitro competition in tissue culture of three flax (Linum usitatissimum L.) cultivars using different distances among hypocotyl explants cultured. Hypocotyl fresh and dry masses, shoot regeneration percentage, shoot number per hypocotyl, regenerated shoot length and total chlorophyll content were examined during shoot regeneration, while plantlet height, number of roots and length of roots were recorded during rooting. With decreasing distance among explants we observed increased shoot regeneration and rooting till a certain point from where stress initiated and significant decreases in all parameters observed. Explants cultured at distance 1.0 cm were found to be at their optimum.

The elucidation of molecular mechanisms underlying the leaf development can be facilitated by the detailed anatomical study of leaf development mutants. We present an analysis of leaf anatomy and morphogenesis during early developmental stages in has mutant of Arabidopsis thaliana. The recessive has mutation affects a number of aspects in plant development, including the shape and size of both cotyledons and leaves. The earliest developmental observations suggest almost synchronous growth of the first two leaf primordia of has mutant. No significant disruption of the cell division pattern in the internal tissue is observed at the earliest stages of development, with the major anatomical difference compared to wild type primordia being the untimely maturation of mesophyll tissue cells in has mutant. At the stage of leaf blade formation, structure disruption becomes clearly evident, by irregular arrangement of the cell layers and the lack of polarity in juvenile has leaves. One distinguishing feature of the mutant leaf anatomy is the absence of mesophyll tissue differentiation. Altered has mutant leaf morphology could be at least partially accounted for by the ectopic STM activity that was found at the base of leaf primordia during early stages of leaf development in has plants.