Morphological Characterization and Transcriptional Regulation of Corolla Closure in Ipomoea purpurea

Corolla closure protects pollen from high-temperature stress during pollen germination and fertilization in the ornamental plant morning glory (Ipomoea purpurea). However, the morphological nature of this process and the molecular events underpinning it remain largely unclear. Here, we examined the cellular and gene expression changes that occur during corolla closure in the I. purpurea. We divided the corolla closure process into eight stages (S0–S7) based on corolla morphology. During flower opening, bulliform cells appear papillate, with pigments in the adaxial epidermis of the corolla. These cells have distinct morphology from the smaller, flat cells in the abaxial epidermis in the corolla limb and intermediate of the corolla. During corolla closure, the bulliform cells of the adaxial epidermis severely collapse compared to cells on the abaxial side. Analysis of transparent tissue and cross sections revealed that acuminate veins in the corolla are composed of spiral vessels that begin to curve during corolla closure. When the acuminate veins were compromised, the corolla failed to close normally. We performed transcriptome analysis to obtain a time-course profile of gene expression during the process from the open corolla stage (S0) to semi-closure (S3). Genes that were upregulated from S0 to S1 were enriched in the polysaccharide degradation pathway, which positively regulates cell wall reorganization. Senescence-related transcription factor genes were expressed beginning at S1, leading to the activation of downstream autophagy-related genes at S2. Genes associated with peroxisomes and ubiquitin-mediated proteolysis were upregulated at S3 to enhance reactive oxygen species scavenging and protein degradation. Therefore, bulliform cells and acuminate veins play essential roles in corolla closure. Our findings provide a global understanding of the gene regulatory processes that occur during corolla closure in I. purpurea.

Organization of leaf vascular system and gas exchange in seedlings of Guazuma ulmifolia Lam. in different light conditions

In tropical forests, different physiological characteristics of leaves in tree species are evidenced by variations in different incident light conditions. We aim to evaluate gas exchange and organization of leaf vascular system in Guazuma ulmifolia Lam. seedlings under different light conditions. Seedlings were obtained from seeds germinated under greenhouse conditions with controlled environment. Ninety days after germination, seedlings in 8kg pots were transferred to the experimental site to allow acclimatization under sun and shade conditions. The experimental design was completely randomized, with two treatments: full sunlight and artificial shading, limiting the luminosity to about 5% of irradiance. Seedlings were maintained under these conditions for 120 days before measuring gas exchange parameters. We measured photosynthetic rate, stomatal conductance, sub-stomatic CO2 concentration, transpiration, and chlorophyll content. Anatomical analysis measured distance between veins, distance from veins to abaxial epidermis, distance from veins to adaxial epidermis, distance from veins to stomata, total leaf thickness, abaxial epidermis thickness, adaxial epidermis thickness, palisade parenchyma thickness, and spongy parenchyma thickness of foliar gas exchange of G. ulmifolia which presented significant differences between light environments. Photosynthetic rate and stomatal conductance were reduced by 78% and 39%, respectively, in shade, while stomatal conductance increased by 31% in full sunlight. Transpiration showed no significant difference between the two treatments, but chlorophyll content was 30% lower in full sunlight. Distance between veins and distance from veins to stomata showed no difference between treatments, but the other parameters increased in full sunlight. Thus, the results showed that the pioneer species G. ulmifolia presented leaf gas exchange acclimated to environments with high luminosity.

Effects of Preplantation Phosphate on the Inner Morphology of Sugarcane Leaves

Phosphorus is considered an essential element for sugarcane, assuming great importance in rooting, tillering and final stem yield. In order to evaluate the effects of pre-planting phosphating on the internal morphology of sugarcane leaves, an experiment with the RB867515 variety was carried out in a randomized block design with 4 replications, in a factorial scheme 2x4, being two sources of phosphorus (decanted phosphate and monoammonium phosphate) and four doses of phosphorus (0; 80; 120; 160 kg ha-1 P2O5). At 120, 240 and 362 days after planting the following characteristics were evaluated: Abaxial epidermis thickness, adaxial epidermis thickness, mesophyll thickness, phloem vessel diameter and phloem vessel diameter. Phosphorus doses influenced the development of sugarcane leaf-bearing vessels at harvest. Concentrations above 160 kg ha-1 the P2O5 presented lower mean phloem diameter values in sugarcane leaves. Concentrations with 80 kg ha-1 the P2O5 presented greater xylem diameter in sugarcane leaves.

Cortical Microtubule Organization during Petal Morphogenesis in Arabidopsis

Cortical microtubules guide the direction and deposition of cellulose microfibrils to build the cell wall, which in turn influences cell expansion and plant morphogenesis. In the model plant Arabidopsis thaliana (Arabidopsis), petal is a relatively simple organ that contains distinct epidermal cells, such as specialized conical cells in the adaxial epidermis and relatively flat cells with several lobes in the abaxial epidermis. In the past two decades, the Arabidopsis petal has become a model experimental system for studying cell expansion and organ morphogenesis, because petals are dispensable for plant growth and reproduction. Recent advances have expanded the role of microtubule organization in modulating petal anisotropic shape formation and conical cell shaping during petal morphogenesis. Here, we summarize recent studies showing that in Arabidopsis, several genes, such as SPIKE1, Rho of plant (ROP) GTPases, and IPGA1, play critical roles in microtubule organization and cell expansion in the abaxial epidermis during petal morphogenesis. Moreover, we summarize the live-confocal imaging studies of Arabidopsis conical cells in the adaxial epidermis, which have emerged as a new cellular model. We discuss the microtubule organization pattern during conical cell shaping. Finally, we propose future directions regarding the study of petal morphogenesis and conical cell shaping.

Cross-sectional anatomy of leaf blade and leaf sheath of cogon grass (Imperata cylindrica L.)

Histology of leaf blade and sheath of cogon grass (Imperata cylindrica L.) Beauv., indicated typical C4 Kranz anatomy. Cells of adaxial epidermis were smaller and bulliform cells were present on the adaxial epidermis. The shape of bulliform cells was bulbous; 3-7 cells were present in a group and 3-5 folds larger than epidermal cells. Three types of vascular bundles in respect of size and structure were extra large, large and small and they were part of leaf blade histology. These three sizes of vascular bundles were arranged in successive manner from midrib to leaf margin. Leaf sheath bundles were of two types: large and small. Extra large bundles were flanked by five small and four large bundles but small bundles were alternate found to be with large typed bundles. Extra large bundles were of typical monocotyledonous type but the large type had reduced xylem elements and the small typed was found to be transformed into treachery elements. Small be bundles occupied half the thickness of the flat portion of leaf blade topped by large bulliform cells of the adaxial epidermis. Extra large and large bundle had been extended to upper and lower epidermis. Kranz mesophyll completely encircled the bundle sheath and radiated out into ground tissue. Midrib was projected in abaxial direction and had a central vascular bundle with large and small bundles on either side of it along the abaxial regions. The midrib vascular bundle was devoid of chlorenchymatous bundle sheath and was of non-Kranz type. Continuous sub-epidermal sclerenchyma girders were noted as adaxial hypodermis. Anatomical traits exhibited an important adaptive defense against draught and saline stress of the plant. Quantitative measurement of various anatomical traits indicated strong variations among them.J. bio-sci. 25: 17-26, 2017

Anatomía vegetativa de Ctenitis melanosticta (Dryopteridaceae, Pteridophyta)

The root, rhizome, petiole and blade anatomy of Ctenitis melanosticta was studied and compared with the available information for closely related genera. Root is diarc with sclerenchyma and parenchyma cells in the cortex, with fungal hyphae exclusively in the latter. The occurrence of sclereid nests in the rhizome is shared with Dryopteris and Campyloneurum. A cortical band was present in petiole and lamina, as in Dryopteris and other genera of the most derived ferns. The lamina had unifacial mesophyll and under the adaxial epidermis there were several layers of the fiber, as described for Elaphoglossum and Thelypteris, but differed from Asplenium, Dryopteris, and Polybotrya with collenchyma. The anatomy of C. melanosticta was similar to that of most species studied of Dryopteridaceae, although with some differences. Additional anatomical studies in species of Dryopteridaceae will allow to confirm the diagnostic value of several anatomical features, such as the lack of cortical band in the rhizome, the sclereid nests, the unifacial mesophyll, and the cortical band in the lamina.

Morphology and epidermal characters of Ginkgo pilifera Samyl. leaves and distribution of this species in the Late Cretaceous of Northern Asia

In the result of investigation of new findings, the variability of leaf shape and epidermal characters of Ginkgo pilifera Samyl. were studied. Geographical and stratigraphic ranges of this species were analyzed on the base of new material and earlier published data. This species was described by Samylina (1967) from the upper part of the Timmerdyakh Formation exposed in the Lena-Vilyui depression in Eastern Siberia. After that many new occurrences of this species were reported. G. pilifera was widely distributed from late Albian to Maastrichtian in Asian part of the Siberian-Canadian paleogeographical region. The earliest occurrence was documented from the late Albian-lower Turonian deposits of the Krivorechenskaya Formation, Grebenka River basin, Northeastern Russia. Approximately in the same time (in the Cenomanian) remains of G. pilifera appeared in the lower part of the Timmerdyakh Formation in the Lena-Vilyui depression. In Western Siberia in the late Albian and Cenomanian other species of Ginkgo were found: G. sertensis N. Nosova et Golovn. and G. chlonoviae N. Nosova et Golovn. were described from the Kiya Formation and G. ragosinii N. Nosova et Golovn. and G. tjukansis Kiritch. were described from the Simonovo Formation. In the Turonian and Coniacian G. pilifera was discovered in the upper part of the Timmerdyakh Formation, in the Valizhgen Formation of Yelistratov peninsula in Penzhina Bay area, in volcanogenic deposits of the Kolyma River basin and in the Derevyannye Gory Formation of New Siberia Island. In the Santonian-Campanian this species was reported from the Arkagala Formation of the Kolyma River basin and from two localities in the Amur River basin: from upper part of the Kundur Formation in Russia and from the Taipinglinchang Formation in China. The last occurrence is the most southern finding of this species. In Maastrichtian G. pilifera penetrated in Western Siberia, that significantly increased its area in western direction. The most variable character in G. pilifera morphology is the leaf shape. Leaves change from entire to deep-dissected into several wide lobes with rounded or truncate apices. Dissected forms occured from late Albian to Coniacian and predominated in the Krivorechenskaya (late Albian-lower Turonian) and the Valizhgen (Turonian-Coniacian) Formations Northeastern Russia.During Santonian-Maastrichtian only entire forms were distributed. The variability of epidermal characters is insignificant. The most variable characters are degree of undulation of the anticlinal cell walls, degree of development of cuticular thickenings and number of stomata on adaxial epidermises and number of trichomes on of abaxial and adaxial epidermises. The specific diagnosis of this species was emended. Remains of G. pilifera occur in allochtonous taphocenosis together with other plants characteristic to riparian habitats. Probably, this species was confined to river valleys and was not connected with swamp environments.Paleoecological implication of great number of papillae and trichomes is steel unclear. Emended diagnosis. Leaves broadly fan-shaped, entire with undulate upper margin with several shallow incisions, or, more rarely, dissected into several wide lobes with rounded or truncate apices. Leaves amphistomatic. Anticlinal cell walls of adaxial epidermis sinuous with amplitude up to 2–3 μm; in costal zones sometimes slightly sinuous or straight. Periclinal walls with cuticular dome-shaped thickenings and rare trichomes. Number and development of cuticular thickenings vary in different areas of leaf lamina and in different leaves. Weak development of thickenings usually correlates with increased number of trichomes. Stomata at abaxial epidermis rare; the papillae of subsidiary cells do not cover the stoma completely. Anticlinal cell walls of abaxial epidermis slightly sinuous or straight. Periclinal walls usually with papillae (12-20 μm long), more rarely, smooth. Trichomes (up to 60–100 μm long) occur rather often. Big trichomes usually consist of 2-3 cells. Stomata at adaxial epidermis orientated irregularly, without formation of regular rows, surrounded by five to seven subsidiary cells. Each subsidiary cell bears a proximal papilla up to 15–25 μm long. These papillae completely cover the stoma.

Anatomical features of leaves of three cultivars of winter wheat (Triticum aestivum L.) and settling the plants by cereal leaf beetles, Oulema spp. (Coleoptera, Chrysomelidae)

Investigations of flag leaves anatomy of three winter wheat cultivars: Almari, Gama and Weneda were carried out as it was state that there are great differences in the intensity of cereal leaf beetle feeding on the leaves. In order to determine the features conditioning the differentiated resistance of these cultivars following parameters were measured: the thickness of leaf blade, the length of trichomes and their density in the adaxial epidermis, the number of silicon cells in 1 mm² epidermis and the thickness of the external cell walls of epidermis. The observations of cross section of the leaves were made in a light microscope and that of surface of the adaxial epidermis in a scanning electron microscope. In this study it was shown that Gama cv. distinguishes of the shortest trichomes with poor density, the lowest number of the silicon cells in 1 mm² and epidermis cells with the thinest walls. This features indicate a poor resistance of Gama cv. against feeding of the pests and give reasons for the presence a much higher number of the cereal leaf beetle larvae (about 100%) than at the extant two cultivars. Dependence between the thickness of leaf blades and the number of larvae of the infesting pests has not been stated.