Embryo position of Castanopsis sclerophylla (Fagaceae) seeds with recalcitrant storage behavior differs from Quercus genus, but response to desiccation shows no difference

In many -but not all- recalcitrant Quercus seeds, water loss during drying only occurs through the scar. Consequently, the embryo axis sitting on the opposite side of the scar is well protected from desiccation. However, whether such a mechanism is common throughout Fagaceae species is unexplored. Similarly, little is known about the desiccation response of other Fagaceae genera. Germination and desiccation tolerance of Castanopsis sclerophylla (Fagaceae) were studied by drying the seeds with silica gel. Fresh seeds had a moisture content (MC) of 36% and germinated to 92.5% when incubated at 15/20°C. Drying seeds to 22.5 and 20.7% MC decreased germination to 27 and 5%, respectively; indicating that seeds are recalcitrant. X-ray computed tomography and photomicrographs showed that the embryo axis of C. sclerophylla is located just below the scar. Regardless of drying occurring either through only scar or the whole pericarp, embryo drying was deemed unavoidable. Nevertheless, germination percentage during drying showed exceptional similarities with the other Fagaceae species.

Morphological, Histological, and Protein Profiling of Tea Embryo Axis at Early Stage of Culture

Tissue culture is an alternative choice of plant propagation either through somatic embryogenesis or in vitro organogenesis techniques. TRI2025 tea clone has been cultured successfully, however, the scientific information related to morphology, histology, and protein profile at an early event of culturing time has not been reported yet. This study aimed to determine the differences between those pathways, in the context of morphology, histology, and protein profile. The explants were the embryo axis of TRI2025 tea clone cultured on two different induction mediums; somatic embryogenesis and in vitro organogenesis induction medium. The results showed that most of the explants cultured on A medium developed to be a globular-like structure at 11-day after culture (DAC), while all explants cultured on B medium showed the initiation stage of in vitro organogenesis. Histological analysis showed meristem reconstruction at shoot apical meristem (SAM) and root apical meristem (RAM) at 11-DAC at explants cultured on B medium, while explants cultured on A medium showed callusing at 21-DAC. Protein profile analysis using SDS-PAGE showed protein bands of 54 and 81 KDa that only appeared at explants cultured on A medium start from 14-DAC, and those two protein bands thought to be a differentiator at the early stages of the two tissue culture techniques. Thus, these parameters can be used as early detection for plant tissue culture, especially in tea.

Anterior expansion and posterior addition to the notochord mechanically coordinate embryo axis elongation

How force generated by the morphogenesis of one tissue impacts the morphogenesis of other tissues to achieve an elongated embryo axis is not well understood. The notochord runs along the length of the somitic compartment and is flanked on either side by somites. Vacuolating notochord cells undergo a constrained expansion, increasing notochord internal pressure and driving its elongation and stiffening. Therefore, the notochord is appropriately positioned to play a role in mechanically elongating the somitic compartment. We use multi-photon cell ablation to remove specific regions of the notochord and quantify the impact on axis elongation. We show that anterior expansion generates a force that displaces notochord cells posteriorly relative to adjacent axial tissues, contributing to the elongation of segmented tissue during post-tailbud stages. Unexpanded cells derived from progenitors at the posterior end of the notochord provide resistance to anterior notochord cell expansion, allowing for stress generation along the AP axis. Therefore, notochord cell expansion beginning in the anterior, and addition of cells to the posterior notochord, act as temporally coordinated morphogenetic events that shape the zebrafish embryo AP axis.

Intermediate Epicotyl Physiological Dormancy in the Recalcitrant Seed of Quercus chungii F.P.Metcalf with the Elongated Cotyledonary Petiole

Control of seed germination and dormancy is important in seed plant adaptation and evolution. When studying seed dormancy of Quercus species, we observed a substantially delayed shoot emergence following a fast root emergence in Quercus chungii F.P.Metcalf. Since epicotyl physiological dormancy (PD) has not been reported in Quercus section Cyclobalanopsis, we examined seed morphology and germination in Q. chungii and aimed to document epicotyl PD in the seeds. The embryo was fully developed in fresh ripe seeds. The elongating cotyledonary petiole pushed the embryo axis out of the seed during germination, which differed from observations in other Quercus species. Shoots emerged from seeds with developing roots after 3 months of warm stratification (35/25 °C), reaching the highest percentage of shoot emergence in seeds after 5 months. Seeds were recalcitrant and displayed a yet unreported epicotyl PD type, for which we propose the formula Cnd(root) ‒ Cp’’ 2b(shoot). Early emergence and development of the root system in Q. chungii seeds with epicotyl PD appears to be a mechanism to maintain a constant water supply to the shoot during plumule development and emergence. Our documentation of seed germination will provide guidance for the conservation and restoration of this species from seeds.

EFFECTIVENESS OF GIBBERELLINS IN BREAKING DORMANCY OF SNAKEFRUIT SEEDS (SALACCA SNAKEFRUIT GEARTNER)

This study aims to examine the effectiveness of gibberellins in breaking dormancy to produce high viability snakefruit (Salacca snakefruit Geartner) seeds. The materials used are snakefruit seeds from Tamareja Village, Donggala Regency, sterile sand media, aquades, and GA3 solution. This research was arranged using a completely randomized design (CRD) with one factor, namely the provision of gibberellin, consisting of five levels of concentration, namely P0 = control (without treatment), P1 = 30 ppm and P2 = 40 ppm P3 = 50 ppm P4 = 60 ppm. each treatment was repeated five times so that there were 25 experimental units. Each experimental unit used 20 seeds. Observation data were analyzed using analysis of variance (ANOVA), followed by Tukey' HSD test if the treatment tested showed a significant effect. The results showed that gibberellin administration effectively broke snakefruit seeds' dormancy and produced seeds with high viability. The higher the gibberellins' concentration would increase germination speed plumule length, radicle length, and faster embryo axis emergence. Gibberellin 60 ppm resulted in germination power 98%, germination rate 20.97 days, plumule length 5.52 cm, radicle length 5.15 cm, and embryo axis emergence 9.2 days.

Polyamine-Mediated Transcriptional Regulation of Enzymatic Antioxidative Response to Excess Soil Moisture during Early Seedling Growth in Soybean

This study examined the expression patterns of antioxidative genes and the activity of the corresponding enzymes in the excess moisture-stressed seedlings of soybean in response to seed treatment with polyamines, spermine (Spm) and spermidine (Spd). At the 4 day after planting (DAP) stage, the excess moisture impaired the embryo axis growth, and this effect is associated with the downregulation of superoxide dismutase (GmSOD1) expression and SOD activity in the cotyledon. Seed treatment with Spm reversed the effects of excess moisture on embryo axis growth partly through enhancing glutathione reductase (GR) activity, in both the cotyledon and embryo axis, although no effect on the GmGR expression level was evident. Excess moisture inhibited the shoot and root growth in 7 DAP seedlings, and this is associated with decreased activities of GR in the shoot and SOD in the root. The effect of excess moisture on shoot and root growth was reversed by seed treatment with Spd, and this was mediated by the increased activities of ascorbate peroxidase (APX), catalase (CAT) and GR in the shoot, and APX in the root, however, only GR in the shoot appears to be regulated transcriptionally. Root growth was also reversed by seed treatment with Spm with no positive effect on gene expression and enzyme activity.

Dissecting the Seed Maturation and Germination Processes in the Non-Orthodox Quercus ilex Species Based on Protein Signatures as Revealed by 2-DE Coupled to MALDI-TOF/TOF Proteomics Strategy

Unlike orthodox species, seed recalcitrance is poorly understood, especially at the molecular level. In this regard, seed maturation and germination were studied in the non-orthodox Quercus ilex by using a proteomics strategy based on two-dimensional gel electrophoresis coupled to matrix-assisted laser desorption ionization/time of flight (2-DE-MALDI-TOF).Cotyledons and embryo/radicle were sampled at different developmental stages, including early (M1–M3), middle (M4–M7), and late (M8–M9) seed maturation, and early (G1–G3) and late (G4–G5) germination. Samples corresponding to non-germinating, inviable, seeds were also included. Protein extracts were subjected to 2-dimensional gel electrophoresis (2-DE) and changes in the protein profiles were analyzed. Identified variable proteins were grouped according to their function, being the energy, carbohydrate, lipid, and amino acid metabolisms, together with protein fate, redox homeostasis, and response to stress are the most represented groups. Beyond the visual aspect, morphometry, weight, and water content, each stage had a specific protein signature. Clear tendencies for the different protein groups throughout the maturation and germination stages were observed for, respectively, cotyledon and the embryo axis. Proteins related to metabolism, translation, legumins, proteases, proteasome, and those stress related were less abundant in non-germinating seeds, it related to the loss of viability. Cotyledons were enriched with reserve proteins and protein-degrading enzymes, while the embryo axis was enriched with proteins of cell defense and rescue, including heat-shock proteins (HSPs) and antioxidants. The peaks of enzyme proteins occurred at the middle stages (M6–M7) in cotyledons and at late ones (M8–M9) in the embryo axis. Unlike orthodox seeds, proteins associated with glycolysis, tricarboxylic acid cycle, carbohydrate, amino acid and lipid metabolism are present at high levels in the mature seed and were maintained throughout the germination stages. The lack of desiccation tolerance in Q. ilex seeds may be associated with the repression of some genes, late embryogenesis abundant proteins being one of the candidates.

SWEET Transporters for the Nourishment of Embryonic Tissues during Maize Germination

In maize seed germination, the endosperm and the scutellum nourish the embryo axis. Here, we examined the mRNA relative amount of the SWEET protein family, which could be involved in sugar transport during germination since high [14-C]-glucose and mainly [14-C]-sucrose diffusional uptake were found in embryo tissues. We identified high levels of transcripts for SWEETs in the three phases of the germination process: ZmSWEET4c, ZmSWEET6b, ZmSWEET11, ZmSWEET13a, ZmSWEET13b, ZmSWEET14b and ZmSWEET15a, except at 0 h of imbibition where the abundance of each ZmSWEET was low. Despite the major sucrose (Suc) biosynthesis capacity of the scutellum and the high level of transcripts of the Suc symporter SUT1, Suc was not found to be accumulated; furthermore, in the embryo axis, Suc did not decrease but hexoses increased, suggesting an efficient Suc efflux from the scutellum to nourish the embryo axis. The influx of Glc into the scutellum could be mediated by SWEET4c to take up the large amount of transported sugars due to the late hydrolysis of starch. In addition, sugars regulated the mRNA amount of SWEETs at the embryo axis. These results suggest an important role for SWEETs in transporting Suc and hexoses between the scutellum and the embryo axis, and differences in SWEET transcripts between both tissues might occur because of the different sugar requirements and metabolism.