Apical Buds Research Articles

Efficient in vitro shoot bud proliferation from cotyledonary nodes and apical buds of Moringa oleifera Lam.

Moringa oleifera Lam. is a quick-growing tree species that has advantages for large-scale production including high yields, high nutrient contents, and diverse industrial applications. To assist such use, we have developed an efficient protocol for in vitro shoot bud proliferation from the plant’s cotyledonary nodes and apical buds. We also investigated the effects of the type of explants, various combinations of plant growth regulators and sucrose contents, and illumination intensity on the proliferation of both types of explants. The results showed that the most suitable tested medium for regenerating shoot buds from cotyledonary nodes was Murashige and Skoog (MS) basic medium supplemented with 1.0 mg/L 6-benzyladenine (BA) and 0.05 mg/L kinetin (KT). This yielded shoots from 66.7% of CNs, and 4.40 shoots per explant on average. In contrast, MS basic medium supplemented with 1.2 mg/L BA and 0.05 mg/L KT was the most suitable tested medium for regenerating shoot buds from apical buds, yielding shoots from 100% of the explants, with 4.13 per explant on average. In addition, increasing the sucrose content of the medium and illumination intensity inhibited their proliferation. MS medium with 0.02 mg/L α-naphthalene acetic acid was suitable for plantlet rooting. The efficient protocol based on these findings reported here may greatly facilitate industrial-scale in vitro generation of uniform seedlings and genetic improvement of the species.

Field Trials to Assess the Growth, Survival, and Stomatal Densities of Five Mexican Pine Species and Their Hybrids under Common Plantation Conditions

Understanding hybridization is important for practical reasons, as the presence of hybrid trees in seed stands can influence the success of natural regeneration and reforestation. Hybridization creates new gene combinations, which can promote or enhance adaptation to new or changing environments. In the present research, we aimed, for the first time, to evaluate and compare the growth and survival of 541 putative hybrid seedlings and 455 seedlings of the pure parental trees of Pinus arizonica, P. durangensis, P. engelmannii, P. leiophylla, and P. teocote, in two reciprocal trials of duration 27 months in the Sierra Madre Occidental (SMO), Durango, Mexico. We also examined the possible correlation between needle stomatal density and seedling growth and survival. The overall analysis of the data showed that the mean height to the apical bud was significantly higher (p = 0.01) in the hybrids than in the pure trees. Considering both trials, the survival rate of P. arizonica (p = 0.002) and P. durangensis (p = 0.01) hybrids was significantly higher than that of the pure trees. The growth parameters were significantly correlated with the mean stomatal density (p < 0.01). Stomatal density and survival at the seed stand level were significantly and positively correlated in the hybrids, but not in the pure trees. In summary, Pinus hybrids generally exhibited the same ability as the pure species (or sometimes a greater ability) to withstand weather conditions, survive, and grow effectively in both growth trials. The systematic use of natural pine hybrids in Mexico could therefore be considered a possible option for sustainable management and as a component of adaptive silviculture.

In Vitro Floral Emergence and Improved Formation of Saffron Daughter Corms

In vitro cormogenesis is a potential tool for improving saffron production under controlled conditions. In this study, the effects of explant type, culture type, and medium supplements on saffron daughter corm formation in vitro were assessed. Saffron flowers emerged 30 days after culture, and the sizes of in-vitro- and ex-vitro-produced flowers and stigmas were similar. In vitro daughter corm formation and the saffron life cycle was completed after 10 and 14 weeks of culture, respectively. Using in vitro intact corms was more effective for corm production than using apical buds. Compared with apical bud explants, mother corm explants produced more corms with a higher fresh weight and diameter. Compared with solid culture, liquid cultures using bioreactors provided corms with a higher fresh weight and diameter, regardless of explant type. An ebb and flow system provided the highest cormlet fresh weight and diameter but the fewest cormlets, whereas an immersion system provided more cormlets with a smaller size. Saffron apical buds cultured with salicylic acid at 75 mg L−1 or glutamine at 600 mg L−1 exhibited the highest cormlet diameter and fresh weight. These findings will improve the process of in vitro cormogenesis and the production of saffron under controlled conditions.

CREATION OF DECORATIVE FORMS OF SCOTS PINE FOR THE GREENING OF URBANIZED ENVIRONMENT

The features of creating decorative forms from Scots pine trees are considered. It has been established that, as a result of mechanical damage (death of an apical bud or an apical shoot) and subsequent regeneration processes in pine trunks, two main directions of post-traumatic deformations of young pine trunks stand out - violation of monopodial branching and occurrence of multi-stemming. In the case of the death of an apical bud or apical shoot, in early spring, the growth of shoots from whorl buds is activated and their vertical reorientation occurs. After a short period of relative multi-stemming, one of the shoots from whorl buds takes the place of the central shoot. Formation of multi-stemming occurs in the case of the death of an apical shoot, mainly in late spring-summer period. There is also an increased growth of shoots from whorl buds and their vertical reorientation. All shoots formed from whorl buds retain their vertical orientation in the future with subsequent formation of several separate stems. It is shown that the processes of mechanical damage-regeneration are also reflected in the condition of trunk wood in the places of damage. In trunk areas where mechanical damage and subsequent regeneration took place, a noticeable increase in the basic density of wood is observed - by 15-20 % in case of shoot replacement and by 25-45 % in case of multi-stemming. The content of late wood also increases - by 10-30 % in case of shoot replacement and by 15-35 % in case of multi-stemming. It is recommended, to create decorative forms, to select pine trees no older than 8-10 years old, with an average growth rate in height. Decorative forms of Scots pine require annual adjustments.

BIOCHEMICAL PROFILE OF EMBRYONIC AND NON-EMBRYONIC CALLUS OF CLERODENDRUM PHLOMIDIS L.

Clerodendrum phlomidis L. (Arani) is a medicinal plant used in the treatment of Diabetes mellitus. Enzymatic studies helps to differentiate between embryonic and non-embryonic callus at very early stage. In vitro experiments were conducted using leaf, stem, node, internode, apical bud as an explant. Callus cultured on MS basal medium supplemented with various combinations of 2, 4-D and Kinetin (1 : 1, 2 : 2, 3 : 3, 4 : 4, 5 : 5 mg/l 2,4-D : Kinetin). Large variations were observed in the callus cultures owing to hormonal variations. Higher hormonal concentration 5 mg/l 2, 4-D + 5 mg/l kinetin resulted in somatic embryoids while lower concentrations 1:1, 2:2, 3:3 mg/l, 2,4-D : kinetin resulted in non-embryonic cells. Enzymatic activities of peroxidase, IAA- oxidase, invertase, protease,  and  amylase, polyphenol oxidase (PPO), catalase and enzyme protein were estimated from cytoplasmic as well as wall-bound fractions of 2, 4, 6and 8 week old callus using standard methods. In two week old culture peroxidase and polyphenol oxidase (both wall bound and cytoplasmic) activity increases in non-embryonic callus and decreases in embryonic callus while IAA oxidase and Protease (both wall bound and cytoplasmic) activity decreases in non-embryonic callus and increases in embryonic callus. Total amylase and α-amylase activity of wall bound enzymes increases in non-embryonic callus and decreases in embryonic callus while cytoplasmic activity decreases in non-embryonic callus and increases in embryonic callus. On the basis of the above study enzymes could serve as a biochemical marker to determine the embryonic and non-embryonic callus at very early stage.

Frequency-dependent predation and seedling fate: Effect of forest litter on regeneration of the Quercus wutaishanica seedling

Rodents attack oak (Quercus wutaishanica) seeds based on their sizes and frequencies before germination. However, the predation of oak seeds post-germination (seedling cotyledons) is not well studied. Here, we not only tested the preference of rodents for oak seedlings from different-sized seeds, but also traced the seedling fate under different litter treatments. We transplanted seedlings with frequency of large and small seed (FLSD) ratios as 1:9, 3:7, 5:5, 7:3, and 9:1, respectively, with each set treated with the litter cleared and covered. Our results showed that small-seeded seedlings were more preferred when the FLSD was 1:9 and 3:7, whereas large-seeded seedlings had a higher preference when the FLSD was 9:1 and 7:3. Moreover, the predation and survival rates of the seedlings decreased when covered with litter, thus indicating that, although forest litter prevented the seedling predation by rodents, it was unfavorable for seedling survival. Furthermore, we found that cotyledon predation by rodents had no significant effect on seedling performance, but their growth was severely inhibited when the apical bud was bitten off, thus suggesting that the apical bud loss was the main cause of seedling recruitment failure. Our study indicates that positive frequency-dependent predation helps maintain the polymorphism of germination type of Q. wutaishanica seedlings. Additionally, in the forest, the presence of litter may change the predation behavior of rodents, which consequently affects the growth and survival of the seedlings. Moreover, future studies should focus on how the forest species’ specific predatory habits and the litter of different thicknesses affect the growth and survival of the oak seedlings, to better understand the renewal mechanism of the oak trees.

Topophysis and Growth Regulators Effects on Buds and Zygotic Embryos Regeneration of African Bush Mango Tree Cultured In vitro

Background: African bush mango tree is an important fruit plant with high nutritional, medicinal, and commercial values. However, its seedling system remained a deep understanding. This study aimed to evaluate the effect of topophysis and growth regulators on the reactivity of different types of buds and zygotic embryos of wild mango.
 Methodology: Ripe fruits from two local varieties (Wossro and Sissro) were pulped. The nuts were extracted and dried for one week under greenhouse. Zygotic embryos were excised from nuts and disinfected with the bleach solution (NaClO 10% with 8% active chloride) for 10 min following by three successive rinsing using sterilized water. The second set of nuts was cultivated for under greenhouse in the polybags containing the sand. One month later, buds from different positions (apical, axillary and cotyledonary) were excised and disinfected with NaClO 10% for 10 min follow by the immersion in a mercuric chloride 0.1% added with two drops of Tween 20 especially for axillary and cotyledonary buds for 5 min while 0.01% of mercuric chloride was used for apical buds. The explants were cultured on ¼MS and ½WPM media supplemented with BAP, KIN at different concentrations (0.2 mg/L and 3.5 mg/L respectively) and NAA (0.05 mg/L).
 Results: The best sprouting rate was obtained with the variety Wossro which showed a high bud break rate (26.47%) against (9.88%) for the variety Sissro. The topophysis significantly influenced the response of the buds in tissue culture. 24.48% of axillary buds were sprouted on ¼ MS medium + 3.5 mg/L BAP+ 0.05mg/L NAA. The in vitro germination of embryos was significantly (p≤ 0.05) influenced by the genotype of the variety. 50.76% of buds were germinated for Wossro while 18.32% were germinated for Sissro. ¼ MS + 0.2 mg/L KIN has significant influenced the plants growth and development.
 Implication: The findings will help to improve the regeneration rate and plantlets production of African bush mango tree.

Frequency-dependent seedling predation by rodents: growth and survival of Quercus wutaishanica in two habitats

Abstract Rodents attack oak (Quercus wutaishanica) seeds based on their sizes and frequencies before germination. However, the predation of oak seeds post-germination (seedling cotyledons) is not well studied. Here, we not only tested the preference of rodents for Q. wutaishanica seedling cotyledons based on the frequency of large- versus small-seeded (FLS), but also evaluated the effects of predation on seedlings growth and survival in different habitats. We transplanted seedlings with the FLS set as 9:1, 7:3, 5:5, 3:7 and 1:9, respectively, in the forest gap and under the canopy in the Liupan Mountains National Nature Reserve in Ningxia Hui Autonomous Region, Northwest China. The results showed that: (i) in 1–7 days after transplanting seedlings, rodents prefer the cotyledon of large-seeded seedings while small-seeded seedlings were preferred in 8–60 days, and the positive frequency-dependent predation was observed. (ii) The cotyledons were preyed on, the apical buds were bitted off, and the whole seedlings were uprooted, which mostly occurred under the forest canopy. At the end of a growing season, the survival rate of seedlings in the forest gaps was more than twice that under forest canopies. (iii) If cotyledons were preyed on, the growth of Q. wutaishanica seedlings would not be affected, but the seedlings growth was severely inhibited when the apical bud was bitten off. These results not only provide new insights into the coexistence between rodents and seedlings of different phenotypes, but also reveal the ecological characteristics of deciduous Quercus regeneration.

A Review on Micropropagational and Phytochemical Aspects of Some Medicinally Important Wetland Plants

Wetlands are places where the soil is always moist. Plants that are found in areas that are always wet are called wetland plants. Sphaeranthus indicus, Eclipta alba and Scoparia dulcis all are wetland plants. The background of this study is to understand the different types of phytochemicals present in these three wetland plants and micropropagation methods using different types of explants. The bioactive constituents contained in these three wetland plants and micropropagation methods using various types of explants were learned from the previous articles. Phytochemicals such as sesquiterpene lactones, eudesmanolides, and flavonoids have been isolated from the plant Sphaeranthus indicus. Eclipta alba has yielded a diverse set of chemical compounds, including coumestans, alkaloids, thiopenes, saponins, quinines, flavonoids, polyacetylenes, triterpenes and their glycosides. The main bioactive compounds contained in the plant Scoparia dulcis are flavonoids, polyphenols, tannins and terpenoids. Micropropagation using different types of explants has been done very successfully for these three wetland plants. Phytochemicals mainly contained in these plants are alkaloids, terpenoids, steroids, flavonoids, coumestan. Explants used for micropropagation are leaf, shoot tip, nodal segments, apical buds, axillary buds and seeds. The main conclusion of this study is that all these plants have many medicinal properties that are yet to be discovered. All of which should be exposed to the latest technologies available in the field. However, the extent to which plant tissue culture can be used in these plants is also a possibility that should be considered.

Growth and Flowering of Saffron (Crocus sativus L.) with Three Corm Weights under Different LED Light Qualities

• Saffron (Crocus sativus L.) is referred ‘red gold’ worldwide as it is the most expensive spice. • The cultivation of saffron has been limited due to low flower yields. • Light emitting diode (LED) emits monochromatic light, which can improve crop quality and yield. • The effects of LED supplementation on growth and flowering of saffron ( Crocus sativus ) with three corm weights were studied. • Monochromatic red light significantly promoted saffron growth and increase stigmas yields with three corm weights. Saffron ( Crocus sativus L.) is a flowering plant whose dried stigma is an expensive and well-known spice. The major goal in saffron cultivation is to improve flower quality and yield. The present research aimed to understand the influence of LED light quality on the growth and flowering of saffron and provide valuable guidance to explore modern techniques to promote flower and stigma yield. The growth characteristics, flowering characteristics, hormone and nutrient content, and stigma quality and value were determined at three different corm weights (20–25 g, 25–30 g, 30–35 g per corm) under six LED light qualities [white (control, CK); monochromatic blue light (B); monochromatic red light (R); red and blue light at 1:2 ratio (R1B2); red and blue light at 1:1 ratio (R1B1); red and blue light at 2:1 ratio (R2B1)]. Monochromatic red light reduced corm biomass loss, accelerated apical bud growth, enhanced flower size and number, and advanced flowering. Monochromatic red light significantly increased the indole-3-acetic acid (IAA), soluble protein (SP), and zeatin riboside (ZR) levels in the mature corms compared with CK. Besides, red light demonstrated the highest hormone and nutrient content for the 30–35 g corm weight. Furthermore, monochromatic red light improved stigma yield (total dry weight), total crocin production, and the practical value ratio of saffron. The present study's observations indicate that monochromatic red light promoted saffron growth, advanced flowering, and increased stigma yield by regulating the corm phytohormones and enzyme activity. The study provides valuable guidance to explore modern techniques to promote saffron flower and stigma yield.

Effect of priming with gibberellic acid on acorn germination and growth of plants of Quercus robur and Q. rubra (Fagaceae)

The effect of pre-sowing priming with gibberellic acid (GA3) solution (50 mg/L) on acorn germination and growth characteristics of 47-day-old plants of Quercus robur and Q. rubra was studied under laboratory conditions. The priming effect varied depending on the oak species and development phase of the plants. After priming, 86% of Q. robur acorns germinated that exceeded the control by 25%, while the number of sprouted acorns of Q. rubra was at the control level and amounted to 85%. The 47-day-old plants of Q. robur were divided into three groups: (1) sprouted acorns with cracked pericarp and main root; (2) seedlings with formed epicotyl and apical bud; (3) seedlings with unopened true leaves of juvenile type. The plants of Q. rubra were divided into two groups: (1) seedlings with formed epicotyl and apical bud; (2) seedlings with open true leaves. In plants of Q. robur, priming caused decrease of biomass in cotyledons, while no visible changes were found for those of Q. rubra. An increase in growth characteristics, fresh and dry biomass accumulation was noted for all Q. robur plants whereas thickening of shoots was observed only in seedlings of the second group. Instead, hormone treatment of acorns of Q. rubra led to inhibition of growth processes in plants of both groups. In general, priming with GA3 solution enhanced germination of acorns and stimulated growth of Q. robur plants and, conversely, slowed the growth of Q. rubra plants. Exogenous GA3 did not eliminate the syndrome of unfriendly seedlings of the studied oak species, but improved the viability of acorns and increased the number of seedlings/shoots.

The Effects of Growth Regulators and Apical Bud Removal on Growth, Flowering, and Corms Production of Two Gladiolus Varieties

Gladiolus is commonly propagated from corms. The multiplication rate of corms is low and to increase the propagation rate, we examined a combination of apical bud removal and the application of growth regulators. The experiments were conducted in two varieties, ‘Rose Supreme’ and ‘White Prosperity’, and over two seasons. The apical buds on the planting corms were either removed or left intact before the same corms were soaked in a suspension with either 100 ppm of benzyladenine (BA), 100 ppm of gibberellic acid (GA3), or pure water. The results showed that apical bud removal increased the number of corms and shoots. GA3 had limited the effect on corm and shoot production, but instead resulted in increased total leaf area and leaf weight per shoot. BA, on the other hand, increased the number of corms and shoots. Overall, the removal of the apical bud plus application of BA increased the number of corms and shoots but reduced the average corm diameter and leaf weight per shoot. This was clearer in ‘Rose Supreme’ than in ‘White Prosperity’. To maximize flower production for the coming season, farmers need to produce a high number of planting corms, but they also need to balance this with a sufficient corm size and the production of flowers of good quality. The application of growth regulators in combination with apical bud removal should be fine-tuned to avoid a situation that leads to the production of too many small or too few large corms.

Induction of dwarf and early flowering phenotypes in Tricyrtis sp. by ectopic expression of LEAFY from Arabidopsis thaliana.

LEAFY (LFY), which encodes a plant-specific transcription factor, plays an important role in the transition from vegetative to reproductive development. Ectopic expression of LFY has been reported to induce dwarfism and early flowering in some model plants. In order to examine the possibility of using LFY for molecular breeding of ornamental plants, we produced and characterized transgenic plants ectopically expressing LFY from Arabidopsis thaliana (AtLFY) in the liliaceous ornamental plant Tricyrtis sp. Nine independent transgenic plants have been obtained, and all of them exhibited dwarf phenotypes compared with the vector control. These transgenic plants could be classified into three types according to the degree of dwarfism: one showed an extreamly dwarf phenotype with smaller leaves (Type I); two showed moderately dwarf phenotypes (Type II); and six showed slightly dwarf phenotypes (Type III). All of Type I, Type II and Type III transgenic plants produced flower buds 1-3 weeks earlier than the vector control. Vector control and Type III transgenic plants produced 1-4 apical flower buds, whereas Type I and Type II transgenic plants produced only a single apical flower bud. Type I and Type II transgenic plants often produced non-fully-opened flowers. Quantitative real-time reverse transcription-polymerase chain reaction analysis showed that the AtLFY expression level generally correlated with the degree of dwarfism. These results indicate that morphological alterations observed in the transgenic plants was induced by ectopic expression of AtLFY. Lower levels of ectopic expression of LFY may be valuable for producing dwarf and early flowering ornamental plants.

EARLY GENERATION SELECTION IN DIFFERENT LOCATIONS IN POTATO BREEDING PROGRAM

In variety development studies through hybridization, it is necessary to make hybridization with the parents suitable for the purpose, to obtain the tubers in seedling generation from the hybrid seeds obtained, and then to proceed to the clonal selection process. In this study, it was aimed to select clones suitable for tuber shape, earliness, table and industrial use in different locations in the first clonal generation stage from the variation created by hybridization between some commercially registered potato varieties, local potato varieties and some clones with superior characteristics. The study was conducted with 3316 clones in Artova and Kazova districts in Tokat province in Turkey. In this year, which was the first clonal selection stage, besides phenotypic characteristics such as breeder's preference, maturity group, tuber defects, skin roughness, skin and tuber flesh color, characteristics such as the number of tubers per hill, tuber yield per hill, average tuber weight, depth of lateral (eye) and apical buds were examined and data on clones belonging to each hybrid family were obtained. Thus, it was decided to proceed to the next selection stage with 918 clones selected due to their compliance with the criteria determined in the first clonal generation stage.

Transcriptomic Analysis of Mature Transgenic Poplar Expressing the Transcription Factor JERF36 Gene in Two Different Environments.

During the last several decades, a number of transgenic or genetically modified tree varieties with enhanced characteristics and new traits have been produced. These trees have become associated with generally unsubstantiated concerns over health and environmental safety. We conducted transcriptome sequencing of transgenic Populus alba × P. berolinensis expressing the transcription factor JERF36 gene (ABJ01) and the non-transgenic progenitor line (9#) to compare the transcriptional changes in the apical buds. We found that 0.77% and 1.31% of the total expressed genes were significant differentially expressed in ABJ01 at the Daqing and Qiqihar sites, respectively. Among them, 30%–50% of the DEGs contained cis-elements recognized by JERF36. Approximately 5% of the total number of expressed genes showed significant differential expression between Daqing and Qiqihar in both ABJ01 and 9#. 10 DEGs resulting from foreign gene introduction, 394 DEGs that resulted solely from the environmental differences, and 47 DEGs that resulted from the combination of foreign gene introduction and the environment were identified. The number of DEGs resulting from environmental factors was significantly greater than that resulting from foreign gene introduction, and the combined effect of the environmental effects with foreign gene introduction was significantly greater than resulting from the introduction of JERF36 alone. GO and KEGG annotation showed that the DEGs mainly participate in the photosynthesis, oxidative phosphorylation, plant hormone signaling, ribosome, endocytosis, and plant-pathogen interaction pathways, which play important roles in the responses to biotic and abiotic stresses ins plant. To enhance its adaptability to salt-alkali stress, the transgenic poplar line may regulate the expression of genes that participate in the photosynthesis, oxidative phosphorylation, MAPK, and plant hormone signaling pathways. The crosstalk between biotic and abiotic stress responses by plant hormones may improve the ability of both transgenic and non-transgenic poplars to defend against pathogens. The results of our study provide a basis for further studies on the molecular mechanisms behind improved stress resistance and the unexpected effects of transgenic gene expression in poplars, which will be significant for improving the biosafety evaluation of transgenic trees and accelerating the breeding of new varieties of forest trees resistant to environmental stresses.

Integrative mRNA and Long Noncoding RNA Analysis Reveals the Regulatory Network of Floral Bud Induction in Longan (Dimocarpus longan Lour.).

Longan (Dimocarpus longan Lour.) is a tropical/subtropical fruit tree of significant economic importance. Floral induction is an essential process for longan flowering and plays decisive effects on the longan yield. Due to the instability of flowering, it is necessary to understand the molecular mechanisms of floral induction in longan. In this study, mRNA and long noncoding RNA (lncRNA) transcriptome sequencing were performed using the apical buds of fruiting branches as materials. A total of 7,221 differential expressions of mRNAs (DEmRNAs) and 3,238 differential expressions of lncRNAs (DElncRNAs) were identified, respectively. KEGG enrichment analysis of DEmRNAs highlighted the importance of starch and sucrose metabolic, circadian rhythms, and plant hormone signal transduction pathways during floral induction. Combining the analysis of weighted gene co-expression network (WGCNA) and expression pattern of DEmRNAs in the three pathways, specific transcriptional characteristics at each stage during floral induction and regulatory network involving co-expressed genes were investigated. The results showed that sucrose metabolism and auxin signal transduction may be crucial for the growth and maturity of autumn shoots in September and October (B1-B2 stage); starch and sucrose metabolic, circadian rhythms, and plant hormone signal transduction pathways participated in the regulation of floral bud physiological differentiation together in November and December (B3-B4 stage) and the crosstalk among three pathways was also found. Hub genes in the co-expression network and key DEmRNAs in three pathways were identified. The circadian rhythm genes FKF1 and GI were found to activate SOC1gene through the photoperiod core factor COL genes, and they were co-expressed with auxin, gibberellin, abscisic acid, ethylene signaling genes, and sucrose biosynthesis genes at B4 stage. A total of 12 hub-DElncRNAs had potential for positively affecting their distant target genes in three putative key pathways, predominantly in a co-transcriptional manner. A hypothetical model of regulatory pathways and key genes and lncRNAs during floral bud induction in longan was proposed finally. Our studies will provide valuable clues and information to help elucidate the potential molecular mechanisms of floral initiation in longan and woody fruit trees.

DPC can inhibit cotton apical dominance and increase seed yield by affecting apical part structure and hormone content

The plant growth regulator mepiquat chloride (1,1-dimethylpiperidinium chloride, DPC) has been successfully used worldwide in cotton production. Fortified DPC (DPC+) can slightly damage young tissues of the epidermis, which has shown potential in cotton chemical topping in China. The underlying mechanism remains unclear. We investigated whether apical meristem and leaf morpho-physiological traits contribute to delayed growth of the main stem and increased seed yield in DPC or DPC+ as a chemical inhibitor. Two different DPC-sensitive varieties (Xinluzao 60, L60; Jinken 1402, JK1402) were field-grown using three different topping treatments manual topping (MT), no topping (NT) and chemical topping (DPC+ and DPC) in irrigated arid lands of Xinjiang for two years. The plant height decreased by 1.4–13.6% for the DPC+ and DPC treatments compared with the NT treatment and increased by 3.8 –9.2% compared with the MT treatment. The thickness of the leaves, palisade tissue (Pt) and spongy tissue (St) increased by 5.1–21.5% under DPC treatment compared with other treatments. The 3-indoleacetic acid (IAA) content of the leaves significantly increased by 25.0–93.8% at 10 days under the DPC treatment compared with that under the MT and NT treatments. The zeatin riboside (ZR) content of the leaves and apical buds increased up to 7.5 times at 40 days under the DPC+ and DPC treatments compared with that under the NT treatment. The accumulation of reproductive organ biomass and proportion of reproductive organ dry matter to total dry matter under the DPC+ and DPC treatments increased by 2.0–39.7% compared with that under the MT and NT treatments. The seed cotton yield between the DPC+ and DPC treatments showed no significant difference. However, the seed cotton yield of JK1402 under the DPC+ and DPC treatments significantly increased by 9.5–11.7% compared with that under the MT and NT treatments. The main stem length was significantly correlated with the stem length of the upper part and gibberellin (GA) content in the apical buds. The leaf Pt and ZR contents were significantly correlated with the boll weight and seed cotton yield. Collectively, the data suggest that improved morpho-physiological traits of the apical part, such as an increase in the IAA and GA contents in the apical buds, leaf Pt and ZR contents, and boll weight, inhibited growth of the main stem and increased seed cotton yield for DPC, which is cheaper than DPC+ as a chemical inhibitor under chemical regulation during the whole growth period.

Gibberellic Acid 4+7 Influences Shoot Growth of Seedling Pecan and Bitternut Hickory

Abstract Shoot development of seedling hickories is slow, limiting their success as viable crops using standard growing techniques. Because hickories are predominantly propagated by seed, we questioned whether gibberellic acid (GA) could be used on seedlings to overcome slow shoot development during juvenility. Treatments of one-year-old seedlings of bitternut hickory [Carya cordiformis (Wangenh.) K. Koch], pignut hickory [C. glabra (Mill.) Sweet], pecan [C. illinoinensis (Wangenh.) K. Koch], kingnut hickory [C. laciniosa (F. Michx.) Loud.], shagbark hickory [C. ovata (Mill.) K. Koch], and mockernut hickory [C. tomentosa (Lam.) Nutt.] began at bud break by applying a solution of 500 ppm GA4+7 dissolved in 95% ethanol directly to apical buds or stem tissue at three-day intervals for 27 days. After 160 days, neither treatment affected caliper of any taxon, although species differences were observed. Compared to nontreated control plants, treatment of buds resulted in a 234% and 144% increase in shoot height of bitternut hickory and pecan, respectively. In a second experiment, the same treatments were implemented on seedlings of bitternut hickory shortly after germination. Only shoot height and dry weight were affected (increased) by application of GA4+7. This study indicates plant growth regulators could be effective at increasing shoot extension of some hickories. Chemicals used in this study: Gibberellic acid 4+7 (GA4+7). Species used in this study: bitternut hickory [Carya cordiformis (Wangenh.) K. Koch]; pignut hickory [C. glabra (Mill.) Sweet]; pecan [C. illinoinensis (Wangenh.) K. Koch]; kingnut hickory [C. laciniosa (F. Michx.) Loudon]; shagbark hickory [C. ovata (Mill.) K. Koch]; and mockernut hickory [C. tomentosa (Lam.) Nutt.].

In vitro establishment and multiplication of Aechmea fasciata (Lindl.) Baker, a bromeliad of commercial interest

Objective: To develop a protocol for the aseptic in vitro establishment and multiplication of Aechmea fasciata (Lindl.) Baker. Design/Methodology/Approach: Different concentrations of NaClO (2, 3, 4, and 5%) were assessed for the aseptic establishment of A. fasciata. During the shoot induction stage, the three following treatments were tested: T1 = 6-benzyladenine + naphthalene-1-acetic acid (BA + ANA; 5 + 2 mg L-1); T2 = zeatin + 2,4-dichlorophenoxyacetic acid (Zea + 2,4-D; 5 + 2 mg L-1); and T3 = control with no plant growth regulators. During the shoot multiplication stage, three more treatments were assessed: T1 = Zea + 2,4-D (2.5 + 1 mg L-1); T2 = Zea + 2,4-D (5 + 2 mg L-1); and T3 = Zea + 2,4-D + gibberellic acid (AG3) (2.5 + 1 + 3.5 mg L-1). To assess the number of cellular events, different nitrate concentrations were tested in the medium (18.8, 39.4, and 60 mM NO3-). Finally, during the shoot regeneration stage, nine treatments derived from the combination of three concentrations of kinetin (KIN: 0, 0.1, and 0.5 mg L-1) and of indole-3-acetic acid (AIA: 0, 0.3, and 0.4) were assessed. Completely randomized designs were used in each stage. Duncan’s test (p ≤ 0.05) was used to compare the means during the shoot induction and multiplication stages. A regression analysis was carried out to study the aseptic establishment and a non-parametric test (Kruskal-Wallis) was made to assess the “amount of microshoots during regeneration” variable. Results: A. fasciata aseptic explants with 4% NaClO were established. Shoot induction was most effective with the BA + ANA (5 + 2 mg L-1) treatment. The highest callus production was reported with the Zea + 2,4-D (5 + 2 mg L-1) treatment. The largest number of microshoots was obtained with high nitrate doses. Meanwhile, the most successful regeneration was achieved with the 0.1 mg KIN L-1 and 0.4 mg AIA L-1 treatment. Study Limitations/Implications: The application of Zea and 2,4-D during multiplication induced callus formation. Findings/Conclusions: Apical bud explants in an MS medium with BA and ANA present organogenesis. The use of Zea and 2,4-D forms calluses in the already established in vitro shoots, which regenerate with the use of KIN and AIA. Better microshoot coloring and development were achieved with MS salts, which have a medium nitrate content.

MdGRF11, a growth-regulating factor, participates in the regulation of flowering time and interacts with MdTFL1/MdFT1 in apple

GROWTH-REGULATING FACTORs (GRFs) are plant-specific transcription factors that play important roles in regulating plant growth, development, and tolerance to stresses. However, there has been no in-depth research on the GRF genes and their roles in apple. A total of sixteen GRF genes were identified in the apple genome (GDDH13 V1.1), that expressed differentially in various tissues, in which the highest expression levels were observed particularly in shoot tips and apical buds. Among MdGRFs, the MdGRF11 was cloned and further investigated. Overexpression of the MdGRF11 in Arabidopsis plants promoted flowering, root elongation and leaf size. Further investigation indicated that MdGRF11 interacts with key flower genes FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1). The transient assays demonstrated that MdGRF11 represses the expression of knotted-like homeobox (MdKNOX19). Furthermore, MdTFL1 can compete with MdFT1 for complex formation with MdGRF11 to regulate the expression of MdKNOX19. Taken together, our results suggest that MdGRF11 protein is involved in fine-tuning of the floral transition possibly through interaction with the MdFT1 and MdTFL1 proteins.