Leaf Initiation Research Articles

Varietal Performance of Maize (Zea mays L.) Strains Under Saline Conditions

Crop yields are highly affected due to physiochemical properties of soil and climatic conditions of the region. The yield of the crop is drastically impacted in terms of final economic product due to problems which occurs in life cycle of the plant under the stress conditions like, stunted growth, permanent wilting, and delay in leaf initiation as well as oxidative stresses at molecular level. Maize (Zea mays L.), widely used as staple food has an ample amount of fats and fibres. Salt stress decreases maize yield and in this regard a hydroponic study was carried out to screen maize genotypes against two salinity stress levels i.e., 10 mol m-3 NaCl and 100 mol m-3 NaCl under hydroponic conditions. Nine (09) hybrid genotypes, i.e., Pioneer 3335 (V1), Pioneer 32F10 (V2), Syngenta 8441 (V3), Pioneer: 33H25 (V4), Pioneer: 3233 (V5), Monsanto 6142 (V6), Syngenta 8711 (V7), Monsanto 6528 (V8), Pioneer 31P41 (V9) were selected for experiment. Statistically, the analysis showed the highest root-shoot length, root fresh-dry weight, and shoot fresh-dry weight with V3 (Syngenta 8441) and the minimum with V1 (Pioneer 3335). The results showed that root length increased by 35% shoot length increased by 34% while total length was enhanced by 34% in syngenta 8441. The results clearly depicted that the best suited variety for salt affected areas can be recommended as Syngenta 8441 whereas the least tolerant was Pioneer 3335 in terms of physiological, physical, and growth characteristics.

Phenological variations in relation to climatic variables of moist temperate forest tree species of western Himalaya, India

Phenology, an important ecological attribute, deals with the development of vegetative and reproductive parts of trees called “phenophases”, which are important determinants of primary productivity and sensitive to climate change. The present study recorded various phenophases of major tree species (i.e., Quercus leucotrichophora, Rhododendron arboreum, and Myrica esculenta) as per the two-digit numerical system of Biologische Bundesanstalt, Bundessortenamt, Chemische Industrie (BBCH) scale. A total of 72 individual trees, twenty-four from each species, distributed between 1400 and 1980 m. a.s.l elevations were tagged and measured fortnightly for two consecutive years (2019–2021) in the moist temperate forest of Western Himalaya and compared with earlier existing records. Various phenophases were correlated with climatic factors along with duration and thermal time for each phenological growth stage. We found 24 growth stages for Q. leucotrichophora and M. esculenta and 28 for R. arboreum distributed across seven principal growth stages (e.g. bud development, 0; leaf development, 1; shoot development, 3; inflorescence development, 5; flower development, 6; fruit development, 7; and fruit maturation, 8) of trees as per BBCH scale. Maximum growing degree was 748.87 and 627.95 days recorded for R. arboreum and M. esculenta during leaf development, and 796.17 days for Q. leucotrichophora during fruit development. Flower emergence was observed pre, during, and post-emergence of new leaves for R. arboreum, M. esculenta, and Q. leucotrichophora, respectively, which varied at spatial scale with previous findings. Longevity of fruit development to ripening took 17, 4, and 2 months, respectively in Q. leucotrichophora, R. arboreum and M. esculenta. Duration of leaf initiation and flowering was positively correlated with climatic variables, whereas, the reverse was observed for fruiting in the studied tree species. The study concludes that the variations in phenophases of the three species were strongly influenced by climatic variations, especially minimum temperature. The result of the present study would be important in enabling us to formulate efficient forest management strategies by understanding the short-term adaptation of the climate-sensitive important tree species in the western Himalaya.

All together now: Cellular and molecular aspects of leaf development in lycophytes, ferns, and seed plants

Recent advances in plant developmental genetics together with rapid accumulation of transcriptomic data on plants from divergent lineages provide an exciting opportunity to explore the evolution of plant morphology. To understand leaf origin in sporophytes of land plants, we have combined the available molecular and structural data on development of leaves with different morphologies in different plant lineages: clubmosses, spikemosses, leptosporangiate ferns, ophioglossioid ferns, marattioid ferns, whisk ferns, horsetails, and conifers. Specifically, we address the peculiarities of proximo-distal, ad/abaxial, and lateral development; presence/absence of mesophyll differentiation into palisade and spongy parenchyma; and type of leaf vascular bundles (collateral and bicollateral). Furthermore, taxon-specific and morphology-specific features of leaf development are considered in the context of the organization of shoot apical meristems (SAMs)—monoplex, simplex, or duplex—that produce leaf primordia. The data available imply that cellular patterns of leaf initiation correlate strongly with the structure of the SAMs but not with further leaf development or morphology. The later stages of leaf development are neither correlated with SAM structure nor with taxonomy. Occurrence and, if available, patterns of expression of homologs of the angiosperm genes responsible for the development of adaxial (ARPandC3HDZ) and abaxial (YABBYandKANADI) leaf domains, or establishment of the leaf marginal meristem (WOX) are discussed. We show that there is no correlation in the set of homologs of TFs that regulate abaxial and adaxial leaf domain development between leaves containing only spongy and no palisade mesophyll (of spikemosses, clubmosses, whisk ferns, horsetails, and most conifers), and leaves differentiated into palisade and spongy mesophyll (of leptosporangiate ferns,Ginkgo,Gnetum, and angiosperms). Expression of three out of four regulators of leaf development in primordia of both leaves and sporangia—C3HDZin spikemosses and whisk ferns,YABBYin clubmosses andKANADIin spikemosses and horsetails—indicates that a sporangium developmental program could have been co-opted as a “precursor program” for the origin of microphylls and euphylls. Additionally, expression of leaf development regulators in SAMs of spikemosses (ARP,C3HDZ, andKANADI), clubmosses (YABBY), leptosporangiate ferns (C3HDZ), and horsetails (C3HDZandKANADI) indicates that at least some mechanisms of SAM regulation were co-opted as well in the pre-program of leaf precursors.

Morphogenesis of leaves: from initiation to the production of diverse shapes.

The manner by which plant organs gain their shape is a longstanding question in developmental biology. Leaves, as typical lateral organs, are initiated from the shoot apical meristem that harbors stem cells. Leaf morphogenesis is accompanied by cell proliferation and specification to form the specific 3D shapes, with flattened lamina being the most common. Here, we briefly review the mechanisms controlling leaf initiation and morphogenesis, from periodic initiation in the shoot apex to the formation of conserved thin-blade and divergent leaf shapes. We introduce both regulatory gene patterning and biomechanical regulation involved in leaf morphogenesis. How phenotype is determined by genotype remains largely unanswered. Together, these new insights into leaf morphogenesis resolve molecular chains of events to better aid our understanding.

First Report of Leaf Spot Caused by Phyllosticta capitalensis on Illiciumdifengpi in China.

Illicium difengpi B. N. Changet al., a shrub with aromatic odor in the Illicium genus, is extensively used as a medicinal plant in China. In June of 2020, a leaf spot on I. difengpi with incidence of about sixty percent was observed in a field located in Guilin (25°4'40"N; 110°18'21"E), Guangxi Province, China. Initialleafsymptoms were roundspotswith gray centers, surrounded by yellow halos. The spots gradually spread and merged. Six samples of symptomaticleaveswere collected from six diseased plants, and they were surface disinfested before isolation. Potato dextrose agar (PDA) was used to culture pathogens. Successively, pure cultures were obtained by transferring hyphal tips to new PDA plates. A total of 10 isolates were obtained from the affectedleaves.Two single-spore isolates (GX-1 and GX-2) were obtained and confirmed to be identical based on morphological characteristics. The representative isolate GX-2 was selected for further study on morphological and molecular characteristics. The colony of isolate GX-2 was about 4 cm in diameter on a PDA plate in 5 days, dark green with a granular surface, and irregular white edge. Conidia were hyaline, unicellular, oval, narrow at the end with a single apical appendage, and 8.2 to 13.8 × 3.7 to 7.2 µm (n= 50). Spermatia were hyaline, bacilliform with swollen ends, 3.8 to 8.9 × 1.3 to 1.9 µm (n= 50). Morphological characteristics of isolate GX-2 were consistent with the description of Phyllostictacapitalensis (Wikee et al. 2013). The internal transcribed spacer (ITS) region, translation elongation factor 1-α (tef1-α), glyceraldehyde-3-phosphate dehydrogenase (GPDH) and actin (ACT) were amplified using primers ITS1/ITS4, EF-728F/EF-986R, Gpd1-LM/Gpd2-LM and ACT-512F/ACT-783R, respectively (Wikee et al. 2013). Sequences were deposited in GenBank with accession numbers OL505439 forITS, OL539429 forACT, OL539430 fortef1-α and OL539431 for GPDH. BLAST analysis in GenBank showed that these sequences were 99 to 100% similar to the correspondingITS(MT649668),ACT(MN958710), tef1-α(MN958711) andGPDH (KU716077) sequences ofP. capitalensis. Also, the phylogenetic tree based on genes of ITS, tef1-α, GPDH and ACTby the maximum likelihood method showed that isolate GX-2 clustered together withP. capitalensis.The pathogenicity tests were carried out on a healthy 3 year-old plant in the greenhouse with 80% relative humidity at 25 °C. Four sterilized leaves were wounded with a needle and inoculated with 20 μL spore suspension (1 × 106spores/ml). Another four sterilized leaves were inoculated with 20 μL sterile water as a control. All plants were incubated in a chamber with 98% relative humidity at 25 ± 1°C. After 12 days, disease symptoms similar to the field were observed on leaves, whereas control plants remained healthy.P. capitalensiswas successfully reisolated only from the inoculated leaves and identified based on morphological characters. P. capitalensiscausedleafspotson various host plants around the world (Wikee et al. 2013), including on tea plants in China (Cheng et al. 2019) and oil palm in Malaysia (Nasehi et al. 2020), but it has not been reported on I. difengpi. Thus, this is the first report ofP. capitalensiscausingleafspoton I. difengpi. This study will provide an important reference for the control of the disease. The epidemiology ofthis disease should be investigated in further research.

Phenology, growth and productivity of rice (Oryza sativa l.) under reduced sunlight intensity and foliar nitrogen application

The field experiments related to the study were conducted at Punjab Agricultural University, Ludhiana and Krishi Vigyan Kendra, Bahowal. There were 20 treatment combinations comprising of four levels of sunlight intensity [control (full sunlight), 50% reduction in sunlight light intensity during 15-45(R15-45), 46-75(R46-75) and 76-105(R76-105) DAT] and five levels of foliar nitrogen application [control (only recommended nitrogen, no foliar spray), spray of 3% urea before (NB), midway(NM), afterwards(NA) and midway-afterwards(NMA) the reduction in sunlight intensity in addition to the recommended nitrogen application]. Radiation level of R15-45 significantly preponed (2-5 days) the occurrence of phenological stages from maximum tillering to physiological maturity. Similarly, R46-75 significantly preponed (3-9 days) the occurrences of flag leaf initiation to physiological maturity. The nitrogen level of NB, significantly delayed the occurrence of flag leaf initiation to physiological maturity stages (2-5 days), NM delayed flag leaf initiation to physiological maturity (2-4 days), NA delayed anthesis to physiological maturity (1-4 days) and NMA delayed panicle emergence to physiological maturity (2-5 days). Plant height of rice was significantly increased due to R15-45 (5.21-5.26%) and R46-75 (6.95-7.61%) and also with foliar nitrogen application levels of NB, NM, NA and NMA by 9.95-9.89, 9.65-10.06, 8.06-7.57 and 9.65-9.29 per cent, respectively. Number of tillers m-2 was significantly reduced (4.71-15.99%) under low light conditions and was increased (5.59-23.34%) with foliar nitrogen application. Yield attributes were affected by the reduced sunlight intensity and foliar nitrogen application. Grain yield was significantly reduced as a result of R15-45 (9.19-11.41%), R46-75 (14.29-16.35%) and R76-105 (8.15-10.67%) and foliar nitrogen application levels of NB, NM and NMA resulted in significant increase the grain yield by 9.32-10.19, 5.74-6.38 and 4.59-5.74 per cent respectively, as compared to control.

Linearised Perturbation of Constant Mass Aspect Function Foliation in Schwarzschild Black Hole Spacetime

We study the linearised perturbation of the constant mass aspect function foliation in a Schwarzschild black hole spacetime. In particular, we investigate the linearised perturbation of the asymptotic geometry of the foliation at null infinity. We show that there is a 4-dimensional linear space for the linearised perturbation of the initial leaf inside the event horizon, corresponding to which the linearised perturbation of the asymptotic geometry of the foliation at null infinity is preserved to be round. For such a linearised perturbation of the initial leaf in this 4-dimensional linear space, we calculate the corresponding linearised perturbation of the energy-momentum vector and the Bondi mass at null infinity. We show that the linearised perturbations of the Bondi energy and the Bondi mass both vanish, and every possible linearised perturbation of the linear momentum can be achieved by a linearised perturbation of the initial leaf in the 4-dimensional linear space.

A single nucleotide substitution in the MATE transporter gene regulates plastochron and the many noded dwarf phenotype in barley (Hordeum vulgare L.)

In higher plants, the shoot apical meristem produces lateral organs in a regular spacing (phyllotaxy) and timing (plastochron). The molecular analysis of mutants associated with phyllotaxy and plastochron would increase our understanding of the mechanism of shoot architecture formation. In this study, we identified mutant mnd8ynp5 that shows an increased rate of leaf emergence and a larger number of nodes in combination with a dwarfed growth habit from an EMS-treated population of the elite barley cultivar Yangnongpi 5. Using a map-based cloning strategy, the mnd8 gene was narrowed down to a 6.7-kb genomic interval on the long arm of chromosome 5H. Sequence analysis revealed that a C to T single-nucleotide mutation occurred at the first exon (position 953) of HORVU5Hr1G118820, leading to an alanine (Ala) to valine (Val) substitution at the 318th amino acid site. Next, HORVU5Hr1G118820 was defined as the candidate gene of MND8 encoding 514 amino acids and containing two multidrug and toxic compound extrusion (MATE) domains. It is highly homologous to maize Bige1 and has a conserved function in the regulation of plant development by controlling the leaf initiation rate. Examination of modern barely varieties showed that Hap-1 was the dominant haplotype and was selected in barley breeding around the world. Collectively, our results indicated that mnd8ynp5 is a novel allele of the HORVU5Hr1G118820 gene that is possibly responsible for the shortened plastochron and many noded dwarf phenotype in barley.

First Report of Leaf Spot of Atractylodes macrocephala Caused by Fusarium commune in Zhejiang province, China.

Atractylodes macrocephala Koidz is a very common herbs in China, also famous for its high medicinal value (Lee et al., 2007). In summer of 2019, in Fuyang county of Zhejiang province, the main production area of China, 74 plants of A. macrocephala from a total of about 300 plants, showed black leaf spots . The incidence of the disease was 25% and increased under high temperature and humidity conditions. Initial leaf symptoms appeared as black or tan spots surrounded by brown margins and expanded irregularly. Finally, large blackish brown spots appeared on the leaves, elliptical or irregular, 1.0 to 1.5 cm in diameter, and then lesions turned necrotic. To isolate the pathogen, small pieces (5×5 mm) from the margin of symptomatic leaves were surface-sterilized with 75% ethanol for 30 s and 2% sodium hypochlorite for 2 min, rinsed five times with sterile water, and incubated on potato dextrose agar (PDA) at 28°C in darkness. Purified colonies were white to pink with densely floccose to fluffy aerial mycelium and peach-orange pigmentation. Macroconidia, usually three-septate, were 26.7 to 43.3×3.1 to 5.3μm (n=50), thin-walled, slightly curved, with apical and basal cells curved when cultured in continuous darkness. Microconidia were mostly aseptate, ovate-oblong, straight to slightly curved, and measuring 5.9 to 14.3×2.3 to 3.9μm in size (n=50). Spherical chlamydospores were produced singly or in pairs from mycelium and spores. These characteristics were consistent with the description of Fusarium spp. (Leslie and Summerell, 2006). To identify the species, the translation elongation factor-1 alpha regions (TEF-1α) and the mitochondrial small subunit (mtSSU) were amplified using primers EF-3/ EF-22 (Palmore et al.,2010 and O'Donnell et al., 1998) and MS3F/ MS3R (Stenglein et al., 2010), respectively. Sequences were deposited in GenBank (MT263720, OM203177, OM203178, OM203179, OM203180, OM203181 and MN853662, MZ028170.1, MZ028171.1, MZ028172.1, MZ028173.1, MZ028174.1). These six isolates clustered in the Fusarium commune clade with 100% and 98% similarity, respectively. To test pathogenicity of every isolate, five 8-week-old potted A. macrocephalae plants were wound-inoculated and mycelial discs of 5-mm diameter were used to inoculate. As a control, five plants were inoculated with 5-mm PDA plugs. All plants were individually covered with a plastic bag and kept in a greenhouse at 25 ± 2°C with a 12-h photoperiod at 70 to 80% relative humidity. Typical symptoms similar to those of the field appeared only in inoculated plants after five days. In addition, a conidial suspension (1×105 spores/ml) was sprayed onto young leaves of three potted healthy plants. Three plants sprayed with sterile distilled water served as controls. After 7 days, typical symptoms were observed on all inoculated leaves. Experiments were replicated three times. F. commune was successfully re-isolated from diseased plants. Based on morphological and molecular identification, the pathogen was identified as F. commune. In China, Alternaria alternata (Zhuang, 2005), A. longipes (Tan et al., 2012), Phyllosticta commonsii (Sang et al., 2006) and Phoma exigua (Zhang et al., 2018) were reported as causal agents of the leaf spot disease of A. macrocephalae. To our knowledge, this is the first report of leaf spot disease on A. macrocephalae caused by F. commune in China. Effective control strategies need to be established to reduce the losses.

HDF1, a novel flowering time regulator identified in a mutant suppressing sensitivity to red light reduced 1 early flowering

Arabidopsis SENSITIVITY TO RED LIGHT REDUCED 1 (SRR1) delays the transition from vegetative to reproductive development in noninductive conditions. A second-site suppressor screen for novel genes that overcome early flowering of srr1-1 identified a range of suppressor of srr1-1 mutants flowering later than srr1-1 in short photoperiods. Here, we focus on mutants flowering with leaf numbers intermediate between srr1-1 and Col. Ssm67 overcomes srr1-1 early flowering independently of day-length and ambient temperature. Full-genome sequencing and linkage mapping identified a causative SNP in a gene encoding a Haloacid dehalogenase superfamily protein, named HAD-FAMILY REGULATOR OF DEVELOPMENT AND FLOWERING 1 (HDF1). Both, ssm67 and hdf1-1 show increased levels of FLC, indicating that HDF1 is a novel regulator of this floral repressor. HDF1 regulates flowering largely independent of SRR1, as the effect is visible in srr1-1 and in Col, but full activity on FLC may require SRR1. Furthermore, srr1-1 has a delayed leaf initiation rate that is dependent on HDF1, suggesting that SRR1 and HDF1 act together in leaf initiation. Another mutant flowering intermediate between srr1-1 and wt, ssm15, was identified as a new allele of ARABIDOPSIS SUMO PROTEASE 1, previously implicated in the regulation of FLC stability.

Impacts of Deficit Irrigation on Photosynthetic Performance, Productivity and Nutritional Quality of Aeroponically Grown Tuscan Kale (Brassica oleracea L.) in a Tropical Greenhouse.

Tuscan kale was grown aeroponically with 5, 30 and 60 min nutrient spraying intervals (defined as 5 minNSIs, 30 minNSIs and 60 minNSIs). Four weeks after transplanting, some 5 minNSI plants were transferred to a 60 minNSI (5 minNSI → 60 minNSI) and 90 minNSI (5 minNSI → 90 minNSI) for one more week. Significantly lower light-saturated rates of photosynthesis and stomatal conductance were observed for plants grown with a 60 minNSI than with a 5 minNSI. However, all plants had similar internal CO2 concentrations and transpiration rates. Reduced light use efficiency but increased energy dissipation was observed in plants grown in a 60 minNSI. A higher nitrate concentration was observed in 60 minNSI plants compared to 5 minNSI and 30 minNSI plants, while all plants had similar concentrations of total reduced nitrogen, leaf soluble protein and Rubisco protein. Plants grown with prolonged NSIs (deficit irrigation) had lower biomass accumulation due to the inhibition of leaf initiation and expansion compared to 5 minNSIs. However, there was no substantial yield penalty in 5 minNSI → 60 minNSI plants. Enhancements in nutritional quality through deficit irrigation at pre-harvest were measured by proline and total soluble sugar. In conclusion, it is better to grow Tuscan kale with a 5 minNSI for four weeks followed by one week with a 60 minNSI before harvest to reduce water usage, yield penalty and enhance nutritional quality.

Optical Parameters of the Tilia Cordata Mill. Assimilation Apparatus

Morphometric indicators of trees' assimilative apparatus, including their reflection and light-absorbing properties, largely determine their physiological processes. Leaf initiation and development depend on chlorophyll resulting from photosynthesis, water absorption, its movement through a tree and evaporation. The aim of the paper is to evaluate leaf optical properties of Tilia cordata Mill. It was found that optical coefficients of leaf blades vary depending on the time of sample collection: at the end of the growing season, the leaf blade absorptance (Ab) ranges from 68.9% to 72.4%. During the intensive formation of Tilia flowers, the Ab coefficient decreases to 59.2%. It starts to rise before the beginning of the Tilia fruit maturation. The transmittance, Tr, is also lower at the period of intense flower development. Estimating NDVI (vegetation index) and LAI (leaf area index) from Sentinel-2 satellite imagery showed that the ratio between these indices (NDVI-LAI) changes during the entire growing season. The NDVI-LAI correlation varied up to the strongest one during the entire phenological cycle.

Terminal ear 1 and phytochromes B1/B2 regulate maize leaf initiation independently.

Higher plants generate new leaves from shoot meristems throughout their vegetative lifespan. The tempo of leaf initiation is dynamically regulated by physiological cues, but little is known about the underlying genetic signaling pathways that coordinate this rate. Two maize (Zea mays) mutants, terminal ear1 (te1) and phytochrome B1;phytochrome B2 (phyB1;phyB2), oppositely affect leaf initiation rates and total leaf number at the flowering time: te1 mutants make leaves faster whereas phyB1;phyB2 mutants make leaves slower than wild-type plants. To test whether PhyB1, PhyB2, and TE1 act in overlapping or distinct pathways to regulate leaf initiation, we crossed te1 and phyB1;phyB2 created an F2 population segregating for these three mutations and quantified various phenotypes among the resulting genotypes, including leaf number, leaf initiation rate, plant height, leaf length, leaf width, number of juvenile leaves, stalk diameter, and dry shoot biomass. Leaf number and initiation rate in phyB1;phyB2;te1 plants fell between the extremes of the two parents, suggesting an additive genetic interaction between te1 and phyB1;phyB2 rather than epistasis. Therefore, we conclude that PhyB1, PhyB2, and TE1 likely control leaf initiation through distinct signaling pathways.

Cascading Impacts of Change in Carbon Dioxide Concentration, Temperature and Precipitation on Horticulture Crops: A Review

The impacts of an increase in carbon dioxide concentration, temperature and precipitation on physiology, yield and biochemical contents of horticulture crops including its mitigation measures are evident globally. This study mainly focuses on South-East Asia and Africa. We have reviewed crop-wise published literature mainly from 2000-2021 regarding the impacts of rising carbon dioxide concentration, temperature and precipitation on horticulture. Visible phenophase changes in horticultural crops such as budburst, leaf initiation, flowering, fruiting, seedling and the overall development stages of the crops are evident from the available literature. The prevalence of many diseases like blight, mildew, abaca, black sigatoka and Pierce’s disease are the results of climate change. Changes in the biochemical content of the horticulture crops such as tannins, flavonol, alcohol level, acidic content, starch, amino acids, lipids, chloroplasts, sugar, organic acids and antioxidants were observed. The recommended mitigation measures throughout the literature are delayed sowing dates, efficient seed varieties, controlled fertilizer use, soil moisture conservation and other biotechnological measures. Salinity, moisture and environmental stress-tolerant crops need to develop for better management of climate change. Breeding of short-duration and heat-tolerant varieties, vulnerability quantification and early warning disease forecasting are some of the important research areas.

Efeito do volume de recipiente e do substrato na produtividade comercial de Limonium sinuatum

Abstract The plug cell volume and the quality of the growing medium during nursery stand out as the most important factors affecting the success of ornamental plants, because they significantly affect biomass accumulation and post-transplant yield. These two technological inputs may also be a source of potential abiotic stress capable of modifying the grower´s profit. The aim of this work was to evaluate the physiological mechanisms involved in the growth of Limonium sinuatum plants in three different pre-transplant plug cell volumes and two different growing media as well as in their transplant to pots or to an amended soil. The hypothesis tested was that the negative effects of these combined abiotic stress sources could limit L. sinuatum growth and yield. Our results showed that, in response to limiting situations of root growth, L. sinuatum plants modified the expanded leaf area, the accumulation of fresh-dry weight and the partitioning of photo-assimilates. The physiological processes identified include the capacity for leaf initiation and expansion, the photosynthetic capacity, the growth rate per unit area and time, and the partitioning of photo-assimilates between different plant organs. Since these responses to different types and degrees of abiotic stress are similar to those found in plants depressed in endogenous cytokinins, we speculate that these hormones may be involved in the results obtained in this work.

Early leaf development of Typha domingensis Pers. (Typhaceae)

ABSTRACT Typha domingensis Pers. (cattail) is a globally widespread aquatic plant that causes significant impacts as an invasive species; this ability is dependent on its photosynthetic capacity that is related to leaves. Thus, understanding leaf development is essential for interpreting shoot growth and the formation of its photosynthetic area. This study investigates leaf ontogeny in T. domingensis from early stages until complete development of primary tissues. Plants were collected from natural wetlands and cultivated in a greenhouse. Rhizomes were then selected, and leaves were removed to enable the emergence of new shoots. Rhizome fragments containing leaves were collected at 1-day intervals until day 7 and were subjected to routine procedures in plant microtechnique. New leaves emerged from lateral buds located along the rhizome. The anatomy of scale leaves differs from that of photosynthetic leaves since they contain solid inclusions without palisade parenchyma. Leaf primordia arose laterally from the shoot apical meristem, which was organized as a tunica-corpus. Final leaf shape was influenced by different meristematic zones: the leaf apical meristem, the marginal meristem, the rib meristem, and intercalary meristems. Most leaf tissues developed basipetally, except for xylem and phloem. Within seven days following leaf initiation, all primary tissues were developed and morphologically functional. Leaf formation of Typha domingensis is similar to that of other monocot species. Leaves of T. domingensis develop very early, providing fully functional photosynthetic tissues, which may have implications for its invasive capacity.

Leaf-based induction of protocorm-like bodies, their encapsulation, storage and post-storage germination with genetic fidelity in Mokara Sayan × Ascocenda Wangsa gold

• First report on direct induction of PLBs Mokara Sayan × Ascocenda Wangsa gold. • Earliest and maximum PLB induction occurred on MS medium fortified with 3 mg L –1 TDZ. • Synthetic seeds were developed encapsulating PLBs with 3 % Na-alginate and 75 mM CaCl 2 . • Better storage of synthetic seeds up to 180 days was attained at 25°C in comparison to 4°C. • RAPD marker-based analysis ensured genetic integrity of synthetic seed-derived plantlets. An innovative and accelerated in vitro mass propagation protocol via direct induction of protocorm-like bodies (PLBs) from leaf sections of orchid hybrid Mokara Sayan × Ascocenda Wangsa gold was developed for the first time. Initially, leaf sections were transferred into Murashige and Skoog (MS) medium supplemented with two cytokinin sources namely, thidiazuron (TDZ) and zeatin with variable concentrations. The earliest (∼8 days) induction of PLBs with maximum number (34 PLBs cm –2 leaf section) and induction frequency (82.8 %) were recorded in MS medium fortified with 3 mg L –1 TDZ. The same medium formulation resulted in the highest growth rate (∼93.7 mg day –1 ) with maximum diameter of PLBs (3.4 mm) when compared with other treatments. Observations on proliferating PLBs under variable pressure scanning electron microscopy illustrated their distinctive growth phases wherein proliferating PLBs exhibited globular shape, typical epidermal texture with a rough surface that steadily became more wrinkled, consisting of basal absorbing hair-bodies and the apical zone forming shoot primordia. Stereo microscopic observations revealed gradual maturation of PLBs, initiation of leaf and shoot primordia. PLBs were encapsulated with calcium-alginate for short-term storage and germplasm exchange. Lower concentrations of sodium alginate (1 and 2 %) produced synthetic seeds that were soft to grip and extremely irregular in shape, whereas higher concentration (4 %) resulted in stiffness of synthetic seeds and reduced germination frequency. The most suitable gel matrix to form uniform spherical beads was optimized at 3 % sodium alginate and 75 mM calcium chloride. Synthetic seeds were effectively stored at 25 °C for up to 180 days. The germination efficiency of synthetic seeds gradually declined after storage at both 4 °C and 25 °C, with synthetic seeds stored at 25 °C being more tolerant than those stored at 4 °C. Even after 180 days of storage, the synthetic seeds that were stored at 25 °C exhibited 71.2 % germination frequency and ∼14 days to germination. Synthetic seeds stored at 4 °C deteriorated rapidly and degenerated completely within 180 days. Random amplified polymorphic DNA marker-based analysis carried out with randomly selected synthetic seed-derived plantlets showed 100 % monomorphism with a total 512 bands of molecular size ranging between 130—2100 bp, ensuring post-storage genetic fidelity.

Strong influence of leaf tie formation and corresponding weak effect of leaf quality on herbivory in eight species of Quercus

Abstract Leaf shelter construction by herbivorous insects can improve leaf quality, sometimes changing resultant herbivory. In two experiments in a Missouri (USA) deciduous forest we quantified the impact of leaf tie construction and changes to leaf quality on subsequent leaf damage. First, using eight Quercus species, we compared damage to single leaves versus experimental leaf ties that had been stocked with either Pseudotelphusa quercinigracella (Gelechiidae) or Psilocorsis cryptolechiella (Depressariidae) to determine how initial leaf quality (total phenolics) influenced damage caused by shelter inhabitants. Skeletonization by leaf tying caterpillars and leaf edge chewing by free feeding species were 12.2× and 1.3× greater on tied than on non‐tied leaves, respectively. July and September leaf phenolic content had a slight positive effect on the probability of skeletonization, none on the probability of edge damage, and a weakly positive or negative effect on the intensity of skeletonization and edge damage, depending on leaf position. Second, we created experimental leaf ties, protected from herbivores, on the same Quercus species to determine whether tie formation changes leaf quality (total phenolics, nitrogen, water, toughness). Tie formation decreased phenolics, but this change was predicted to add only 0.8% leaf area loss. Synthesis. Herbivory increased dramatically when leaves were in ties, with the effect mostly due to the tie itself rather than a change in leaf quality. We predict that the advantages of building and using leaf ties in this system are more likely to be escape from natural enemies and changes in abiotic factors.

The Formation of Shapes: Interplay of Genes during Leaf Development Processes

Leaf shape, as one of the clearest manifestations of plant morphology, shows considerable variation owing to genetics and the environment. Leaf initiation occurs in the peripheral zone of the SAM and goes through the three overlapping phases of leaf primordium initiation, leaf dorsiventral development, and leaf marginal meristem establishment. Transcription factors, such as KNOX, WOX, and CUC; hormone-regulating genes, such as GA2ox, GA20ox, and PIN1; and miRNAs such as miR164/165 are tightly involved in leaf shaping through the generation of intricate cooperative networks in different temporal phases and specific tissue zones. Here, we briefly discuss the critical interplay occurring between certain genes and the pivotal role these play in the leaf developmental network and phytohormone regulation, including AS1/AS2–KNOX–GA20ox–GA, miR164–NAM/CUC–PIN1–auxin, and CUC–BAS1/CYP734A–BR, and we attempt to summarize several basic insights into the mechanisms of leaf shape regulation.

Transmission and distribution of Xylella fastidiosa subsp. pauca in olive trees as a parameter for managing olive quick decline syndrome

AbstractSystemic bacteria such as Xylella fastidiosa can be vertically transmitted by using diseased propagative material during nursery tree production. We tested the hypothesis that X. fastidiosa is not transmitted by symptomless olive tree sprouts. In addition, we investigated the distribution of bacteria in olive plants (different parts of canopy and root system) with initial leaf scorch symptoms and with symptoms spread throughout the canopy. In both studies, the presence of bacteria was tested by quantitative real‐time PCR (qPCR). For the first hypothesis, sprouts from a symptomless olive tree were rooted and checked for X. fastidiosa infection 32 months later. A total of 57.7% (41 of 71) of rooted seedlings were positive for X. fastidiosa (Ct from 24.25 to 31.82) but only one plant had scorched leaves. Regarding the distribution of the bacteria in the diseased plants, results based on qPCR showed that X. fastidiosa was systemically distributed through the olive plant canopy (30% to 77% of sampled tissues, with Ct values from 19.56 to 31.59). Samples from trees showing symptoms of olive quick decline syndrome (OQDS), taken 3 m above the lateral branch with symptoms, were positive for the presence of X. fastidiosa, as was the root system. The results demonstrate that vegetative material from olive plants used for rooting must be carefully selected for the absence of X. fastidiosa. Also, based on the qPCR‐positive results, pruning may have a limited effect on eliminating the bacteria from diseased plants, even from the ones showing few OQDS symptoms.