Research Progress of Flower Bud Differentiation of Apple

Flowering is a prerequisite for apple fruiting,and apple flower buds are mixed buds,that is,the vegetative organs and flower structure exist in the same terminal bud simultaneously,which are formed in the year before flowering and fruiting,mainly including spur terminal buds and axillary buds.The infrequent formation of flower buds during its growth and biennial bearing are closely related to flower bud differentiation.Therefore,this paper reviews the research progress of flower bud differentiation of apple from the morphological differentiation,plant hormones and flowering-related genes,in order to provide a theoretical reference for efficient cultivation and stable yield of apple.

Effect of Shoot Control on Flower Bud Differentiation,Flowering,and Fruit Setting in Zanthoxylum armatum DC.

In this study,newly sprouted shoots of Zanthoxylum armatum(Z.armatum),which were collected after the harvesting period,were used as the primary experimental specimens.A randomized block design and paraffin sectioning method were used to investigate the flower bud differentiation process and the quantity and vitality of buds.Furthermore,the study examined the response of flowering and fruiting to cultivation methods for shoot growth,including layering and plant growth regulator application.The results showed that(a)layering and application of plant growth regulators for Z.armatum accelerated the process of flower bud differentiation by approximately 20 days compared to the control group.Additionally,both shoot control methods generated more and larger bud primordia and perianth primordia during the same differentiation phase.(b)The application of plant growth regulators resulted in well-developed buds,exhibiting higher levels of flower bud differentiation than the layering method.The quality of flower bud formation for both shoot control methods was superior to that of the control group.(c)The flowering phenological period was relatively consistent between the two cultivation methods,but the fruit maturity phase for shoot-controlled trees occurred 20 days earlier than the control group.(d)Both layering and the application of plant growth regulators significantly decreased the rates of unfertilized flower shedding and fruit shedding.However,no significant difference was noted in fruit setting per inflorescence and per flower between the two methods and the control.The effect of altitude for both methods on the fruit setting was not significant.Under both shoot control methods,the Z.armatum exhibited earlier morphological differentiation of flower buds,faster differentiation process,improved flower bud quality,and significantly decreased rates of flower and fruit shedding.Thus,these cultivation methods demonstrated the potential to promote flowering,improve fruit setting,and reduce fruit shedding in Z.armatum.

Paraffin section observation of flower bud differentiation of Chimonanthus praecox in Kunming and comparison of the differentiation processes in different regions,China

Chimonanthus praecox is an important ornamental plant and cut flower material in China.It blooms in the freezing winter and its flower emits charming fragrance.However,in different region the flowering time is variable.In order to understand the flowering mechanism of Ch.praecox in the winter,we studied the flower bud differentiation in Spring City-Kunming using paraffin sectioning method in the present study.Meanwhile we compared the differentiation process difference from different regions.It was found that the temperature is the key factor for its flower bud differentiation and blossom of Ch.praecox.In the process of bud differentiation,the temperature 20℃was the optimum for inducing changes from vegetative axillary buds to reproductive buds and subsequent morphological differentiation in Ch.praecox.Furthermore in the first three differentiation periods—tepal primordial stage,staminal primordial stage and pistil primordial stage,Kunming took the shortest time to finish the process due to very rapid temperature rise to 20℃,whereas,in Zhengzhou the time for these differentiations was the longest,which may be caused by the slow temperature rise.After May,the high temperature stress forced the flower buds into the first long dormant period in all regions except Kunming.In Kunming,the average temperature was only 20–25℃,so the flower bud continued to differentiate.In all regions,Kunming is the first to complete whole flower bud differentiation even on the early August,and started the second dormancy very early but very long.In the other regions,the plants went through a shorter dormancy and the low temperature broke the dormancy rapidly.Contrarily the plants of Kunming spent a longer period for the low temperature.Thus,the low temperature less than 10℃is a key factor to breaking the second dormancy.Surely the regular effects of temperature on flower bud differentiation and blossom is very helpful for florescence regulation of Ch.praecox.

Changes in Nutritive Materials in Off-season Mango in Flower Bud Differentiation Stage

Under off-season production mode, change laws of nutritive materials in leaves of fruiting mother branches of mango in flowering process induced by dif- ferent agents were investigated. The results showed that the flowering time of manga trees in the potassium nitrate treatment was earlier than the ethephon treatment by 7 d, and changes trends of materials in leaves of the potassium nitrate and ethephon treatments were substantially the same. The nutritive materials in leaves showed trends of increasing at first and decreasing then. In early flower bud differentiation stage, soluble sugar and starch in leaves increased rapidly, and content of soluble protein also increased rapidly and showed its their peak values, thereby providing energy substances and structural substances demanded by flower bud formation. With flower bud differentiation going on, soluble sugar, starch and soluble protein decreased gradually. It was indicated that the accumulation of soluble sugar, starch and soluble protein is beneficial to flower bud differentiation.

Expression of AP1 Gene During Off-season Flower Bud Differentiation of Mango

This study was conducted to investigate changes in the expression of AP1 gene in flowering process. Potassium nitrate and ethephon were sprayed on 7- year-old Guifei trees out of season. The results showed that AP1 gene had a higher expression level in terminal buds, and especially, the expression level increased significantly in late stage of flower bud differentiation. Potassium nitrate and ethephon promoted flower bud differentiation, and the expression level of AP1 gene in- creased in flowering process remarkably. Expression ofAP1 gene of the potassium nitrate treatment was significantly greater than that of the ethephon treatment and the CK.

Observation on Flower Bud Differentiation of Crape Myrtle in Red Soil Environment

Flower bud differentiation is a key component of plant blooming biology and understanding how it works is vital for flowering regulation and plant genetic breeding,increasing the number and quality of flowering.Red soil is the most widely covered soil type in the world,and it is also the most suitable soil type for crape myrtle planting.The flower buds of crape myrtle(Lagerstroemia indica)planted in red soil were employed as experimental materials in this study,and the distinct periods of differentiation were identified using stereomicroscopy and paraffin sectioning.We optimized the steps of dehydration,transparency,embedding,sectioning and staining when employing paraffin sections.When seen under a microscope,this optimization can make the cell structure of paraffin sections obvious,the tissue structure complete,and the staining clear and natural.The flower bud differentiation process is divided into 7 periods based on anatomical observations of the external morphology and internal structure during flower bud differentiation:undifferentiated period,start of differentiation period,inflorescence differentiation period,calyx differentiation period,petal differentiation period,stamen differentiation period,and pistil differentiation period.The differentiation time is concentrated from the end of May to mid-June.Crape myrtle flower bud differentiation is a complicated process,and the specific regulatory mechanism and affecting elements need to be investigated further.

The structures of floral organs and reproductive characteristics of an ornamental bamboo species,Pleioblastus pygmaeus

As a woody grass,bamboo has special reproductive habits with an extremely long vegetative phase.Pleioblastus pygmaeus is a kind of ornamental dwarf bamboo species with high ecological and economic value in China.There was no documentary record of the flowering of P.pygmaeus until 2015,which bloomed in the Bamboo Garden of Nanjing Forestry University.Generally,bamboo plants rarely bear fruit or have a low seed setting rate,but this species has a high seed production.This study explores developmental reasons using anatomical methods.The process of flower bud differentiation and a series of important reproductive development processes including anther wall development,microsporogenesis,megasporogenesis,male and female gametophyte development,and embryonic development were investigated sequentially.Each stamen contained three tetrasporangiate anthers and the development of anther wall was of Monocotyledonous type.The microspores finally matured into 3-celled pollen grains by two successive mitoses.The pistil was composed of three carpels,with an anatropous,tenuinucellate and bitegmic ovule in a single ovary.The formation of embryo sac belonged to Polygonum type.With three mitoses,functional megaspore developed into the embryo sac with eight nuclei within seven cells.The development of stamen and pistil was synchronous in the same floret.The development of embryo followed Grass type and the development of endosperm belonged to Nuclear type.The development of endosperm was earlier than that of embryo.The study enriches basic knowledge of reproductive biology of bamboo plants and is of great fundamental significance to furtherly explore flowering mechanism of P.pygmaeus and to cultivate bamboo plants sustainably.

Effect of Different Growth State of Broccoli (Brassica oleracea var. italica) on Low Temperature Induction

In order to study the responding of different growth state on low temperature in Broccoli (Brassica oleracea var. italica), we took prematurity broccoli hybrid as the objects. It was found that growth state was varied under different sowing time , moreover, stem became wider with the increasing of light density at the same leaf age. Seedling age of responding to low temperature vernalization only when they grew five leaves above and with over 3.03 ±0.07 centimeter stalk width in 'Qingfeng Broccoli 103'. The older leaf age was and the stronger plant was, the more sensitive and the shorter demanded duration time on low temperature was, and the shorter time required when the plants entered into critical period of floral bud differentiation.

Endogenous phytohormones and the expression of flowering genes synergistically induce flowering in loquat

Flowering is an important process for the reproduction of higher plants.Up to this point,the studies on flowering have mostly focused on the model plant Arabidopsis thaliana,and the flowering mechanism of fruit trees remains mostly unknown.The diversity of the flowering time of loquat(Eriobotrya japonica Lindl.)makes it an ideal material to study the regulation of flowering.In this study,we first observed the inflorescence bud differentiation in two varieties of loquat that had different blooming times(cv.Dawuxing(E.japonica),that blooms in the fall and cv.Chunhua(E.japonica×Eriobotrya bengalensis Hook.f.)that blooms in the spring)and found that the starting time of inflorescence bud differentiation and the speed of inflorescence development were responsible for the difference in blooming times.The determination of endogenous phytohormones by high performance liquid chromatography(HPLC)indicated that abscisic acid(ABA),zeatin(ZT),and gibberellin(GA3)promoted flowering in loquat,while indole-3-acetic acid(IAA)was mainly involved in inflorescence bud differentiation in Chunhua.A transcription level analysis illustrated that multiple flowering-related genes could respond to different signals,integrate to the TFL1,AP1 and FT genes,and then synergistically regulate flowering in loquat.Thus,this study provides a new insight into flowering regulation mechanisms in loquat.

Flower Development and Anatomy of Agapanthus praecox ssp. orientalis (Leighton) Leighton

Floral buds of Agapanthus praecox ssp. orientalis were observed under dissecting and optical microscope to characterize floral organs development and to study relationships between anther development and microsporogenesis. Floral organs differentiation was comprised of 6 distinct stages including nought differentiation, inflorescence bud differentiation, floret primordia differentiation, tepal primordia differentiation, stamen primordia differentiation, and pistil primordia differentiation. Six tepals differentiated almost simultaneously which cross arranged in space and appeared in hexagonal distribution pattern. Six stamens were differentiated inside the tepals at the same time. Finally, 3 carpel primordia differentiated and formed syncarpous pistil. The whole process of floral bud differentiation took approximately 40 d with the first 3 stages developing more slowly than the later 3 stages. Morphology and color of the anther underwent obvious changes during the period between stamen primordia differentiation and anther maturation. Microspores also underwent significant development during this same interval. The relationship between the process of microsporogenesis and anther development has already been made clear by the sauash techniaue.

Study on Reproductive Growth Characteristics and Seed Germination of Eucalyptus dunnii in Sichuan Province

Studying the flowering development and seed germination of Eucalyptu dunnii and mastering the reproductive growth law can provide a theoretical basis for seed garden construction. In this study,a blooming plant growing in Zitong County was selected as the experiment subject. The results were as follows： florescence date of Eucalyptus dunnii was Mid-late February to mid to late October. Depending on morphologic change,flowering can be divided into 6 phases： Flower bud differentiation stage,inflorescence formation stage,opercle color change stage,capsule enlargement and shedding ring formation stage,flowering period,seed development stage. The development process of the buds on the same inflorescence was basically the same,the growth of buds near the base of the same branch was faster than that of the top buds,and the development of flower buds in different positions was random. There were 3-4 ovary cavities in a capsule. The number of shriveled seeds was far more than the number of effective seeds,and the average of each capsule contained five normal seeds which could develop into seedlings.

Sorbitol induces flower bud formation via the MADS-box transcription factor EjCAL in loquat

Sorbitol is an important signaling molecule in fruit trees. Here, we observed that sorbitol increased during flower bud differentiation(FBD) in loquat(Eriobotrya japonica Lindl.). Transcriptomic analysis suggested that bud formation was associated with the expression of the MADS-box transcription factor(TF) family gene, EjCAL. RNA fluorescence in situ hybridization showed that EjCAL was enriched in flower primordia but hardly detected in the shoot apical meristem. Heterologous expression of EjCAL in Nicotiana benthamiana plants resulted in early FBD. Yeast-one-hybrid analysis identified the ERF12 TF as a binding partner of the EjCAL promoter. Chromatin immunoprecipitation-PCR confirmed that EjERF12 binds to the EjCAL promoter, and β-glucuronidase activity assays indicated that EjERF12 regulates EjCAL expression.Spraying loquat trees with sorbitol promoted flower bud formation and was associated with increased expression of EjERF12 and EjCAL. Furthermore, we identified EjUF3GaT1 as a target gene of EjCAL and its expression was activated by EjCAL. Function characterization via overexpression and RNAi reveals that EjUF3GaT1 is a biosynthetic gene of flavonoid hyperoside. The concentration of the flavonoid hyperoside mirrored that of sorbitol during FBD and exogenous hyperoside treatment also promoted loquat bud formation. We identified a mechanism whereby EjCAL might regulate hyperoside biosynthesis and confirmed the involvement of EjCAL in flower bud formation in planta. Together,these results provide insight into bud formation in loquat and may be used in efforts to increase yield.

Comparative transcriptional analysis and identification of hub genes associated with wing differentiation of male in Aphis gossypii

Background:Aphis gossypii Glover(Hemiptera:Aphididae),a worldwide polyphagous phloem-feeding agricultural pest,has three wing morphs(winged parthenogenetic female,gynopara,and male)in the life cycle.The exclusive males could fly from summer hosts to winter hosts,which are essential for gene exchanges of cotton aphid populations from different hosts or regions.However,the molecular mechanism of wing differentiation of male in A.gossypii remains unclear.Results:Morphological observation of male A.gossypii showed that there is no distinct difference in the external morphologies of the 1st and 2nd instar nymphs.The obvious differentiation of wing buds started in the 3rd instar nymph and was visible via naked eyes in the 4th instar nymphal stage,then adult male emerged with full wings.According to morphological dynamic changes,the development of wings in males were divided into four stages:preliminary stage(the 1st instar to 2nd instar),prophase(the 3rd instar),metaphase(the 4th instar),anaphase(the 5th instar).Results of feeding behavior monitoring via EPG(electrical penetration graph)technology indicated that although the male cotton aphids had strong desire to feed(longer duration of C 55.24%,F 5.05%and Pd waves 2.56%),its feeding efficiency to summer host cotton was low(shorter E13.56%and E2 waves 2.63%).Dynamic transcriptome analysis of male aphid at 5 different developmental periods showed that in the 3rd instar nymph,the number of up-regulated DEGs was significant increased,and time-course gene transcriptional pattern analyses results also showed that numerous genes categorized in clusters 3,5,and 8 had the highest expressed levels,which were consistent with morphological changes of wing buds.These results indicate that the 3rd instar nymph is the critical stage of wing bud differentiation in males.Furthermore,through pathway enrichment analysis of DEGs and WGCNA,it revealed that the neuroactive ligand-receptor interaction,Ras signaling pathway,dopaminergic synapse,circadian entrainment and the corresponding hub genes of PLK1,BUB1,SMC2,TUBG,ASPM,the kinesin family members(KIF23,KIF20,KIF18-19)and the novel subfamily of serine/threonine(Aurora kinase A and Aurora kinase B)probably played an important role in the critical stage of wing bud differentiation.Conclusion:This study explored morphological changes and genes transcriptional dynamics males in cotton aphid,revealed the phenomenon of low feeding efficiency of winged males on summer host cotton,and identified key signaling pathways and potential hub genes potentially involved in wing bud differentiation of male in A.gossypii.

Floral gradient in flowering tobacco in relation to free amino acids

By employing TCLs (thin cell layers) culture, the floral gradient in flowering tobacco of different developmental stages was confirmed. The TCLs from early flowering tobacco regenerated more floral buds than those from the tobacco plants in full blooming or fruiting stages. Analysis of free amino acid levels revealed the acropetal gradient of Pro in flowering tobacco stem. L-Pro. L-Trp. D,L-Met and L-Arg were respectively added into the culture medium for testing their influence on floral bud formation from tobacco pedicel segments. Only L-Trp evidently enhanced the floral bud neoformation.