Trichomes Study On The Morphological Structure And Chemical Composition Of Rosa Roxburghii

Rosa roxburghii Tratt(RR)belongs to the Rosaceae.The fruit and sepal of RR is covered with a thick visible coat of prickles(Special form trichomes).The dense trichomes in fruit surface of RR is inconvenient to improve the quality of fresh and processed products.Rosa roxburghii Tratt.f.esetosa K u(RRE)is generally considered a smooth-fruit variant that arose from RR.At present,the morphological structure,developmental process and chemical composition of trichomes in RR have not been systematically studied,and its formation and regulation mechanism are still unclear.In this study,RR of ‘Guinong 5’ and its related species RRE were used as materials,and LM,SEM,TEM,FTIR and other technologies were used to study the morphological structure,development pro cess and chemical composition of trichomes in two germplasm.The main results obtained are as follows:1.Distribution and morphology of trichomes in RR and RRE.Binate prickles arose on the stem nodes in both germplasms.Trichomes on the fruit of RR were macroscopic and of acicular shape.Though the fruit of the RRE looked macroscopic smooth,under scanning electron microscopy(SEM),RRE exhibited polymorphic trichomes of flagelliform,triangular,capitate glandular,and elliptic glandular shapes on the pericarp.O n the surfaces of sepals in RR,there are thick macroscopic acicular trichomes.In contrast,RRE sepals presented flagelliform trichomes and capitate glandular trichomes.It is interesting that no trichomes were found on the surfaces of the marginal lobule of sepals(MLS)in the two germplasms.However,stomata were densely packed on the MLS of RRE when compared to RR.Under stereo microscopical observation,the leaf surfaces of RR and RRE only have long stem capitate glandular trichomes on the principal vains,and there were no trichomes on the leaf blade adaxially and abaxially,but symmetrical 2-row trichomes was found on both sides of the petiole.Interestingly,with increasing of leaf age,the principal vains of two germplasm are found the capitate glandular trichomes development of four stages: The ? stage of trichomes,with a long stem structure,the capitate glandular trichomes which the head cells haven’t periclinal and anticlinal division is not obvious;The ?? stage of trichomes,the head cells are periclinal and anticlinal division,the capitate glandular trichomes appear round and head cells;The ??? stage of trichomes,the head cells burst;The ?V stage of trichomes,with disappearing of the head cells,the capitate glandular trichomes transform into acicular prickle.2.Internal structure of trichomes in RR and RRE.SEM and transmission electron microscopy(TEM)showed that a transection of stem prick les in the two germplasms were composed of epidermis,meristematic layer,and parenchyma cells.Although the transection of acicular trichomes in sepal and fruit of RR was composed of epidermal layer and parenchyma cells,there were significant differences in the morphology of the cells.Former the epidermal cells morphology show polygon,oval for a variety of configuration,and latter the epidermal cells morphology only have oval.The cells of stem prickle both RR and RRE are oval in shape,with large vacuole,large nuclei,it had not prominent nucleoli and other organelles;The cells wall of stem prickle in RR is thick,and other substances are contained in the intercellular space of RR,while the cells wall of stem prickle in RRE is thin,and the substances were no observed in the intercellular space of RRE.The fruit acicular prickle of RR and the fruit flagelliform trichomes as well as the capitate glandular trichomes in RRE were similar at cells morphology,arrangement of cells,the size of the vacuole,and intercellular space,however,the cells in fruit acicular prickle of RR have a few of mitochondrias and golgi apparatus.The both of the fruit flagelliform trichomes as well as the capitate glandular trichomes in RRE exist a small amount of osmium particles,and the capitate glandular trichomes in RRE still exist the endoplasmic reticulum and white body.The cells of sepal acicular prickle in RR and the capitate glandular trichomes of sepal in RRE were similar vacuole size,arrangement of plasmids in cells,content of cytoplasm,and intercellular space.However,the cells morphology of them are different,and there were endoplasmic reticulum and a few osmiophilic granules in the capitate glandular trichomes of RRE;The flagelliform trichomes in sepal of the two germplasm are composed of oval and long as well as narrow cells.Although the flagelliform trichomes in sepal of the two germplasm had the same internal structure that it have the white bod y,endoplasmic reticulum and jagged structure,approximately,the flagelliform trichomes in sepal of RR show a few of mitochondria,with thin wall,high content of cytoplasm and evenly distribution,to the contrary,the cells wall was thickness and low content of cytoplasm of the flagelliform trichomes in sepal of RRE,and we had also found a small amount of heavy particles of osmium of the flagelliform trichomes in sepal of RRE.This difference in cell structure may be related to different developmental processes or biological functions of the trichomes.3.Chemical components of trichomes in RR and RRE.The chemical compositions of stem prickles two germplasms as well as sepals and fruit surface prickles of RR were analyzed by Fourier transformed infrared(FTIR).The results showed that the histochemical compositions of prickles mainly included four kinds of substances,such as lignin,cork,cellulose and hemicellulose,b ut there were significant differences in their contents.O n the whole,the content of lignin and cork in stem prickle of RR was higher than that of RRE,while the content of cellulose and hemicellulose was lower,and the content of components at the base of stem prickle was higher than that at the top of prickle.The results showed that the content of corkscrew,cellulose and hemicellulose in acicular prickle was the highest,followed by stem prickle and sepal acicular prickle was the lowest.The lignin content was the highest among stem thorns,followed by acicular fruit prickles,and the lowest among sepal prickles,which were consistent with their hardness.The fruit acicular prickle of RR has higher content of cork,lignin,cellulose and hemicellulose than the base.The acicular prickle base of sepal in RR contains higher content of cork than the top,while the lignin content is the opposite,cellulose and hemicellulose content is almost the same.Further observation of lignin staining showed that the lignin in both the fruit and sepals of RR was deposited from top to bottom,from the outside to the inside,leading to a similar hardening process.In addition,there was no obvious lignin staining limit at the base of stem thorn of RR,while the stem thorn o f RRE was more obvious,which may lead to different degree of shedding difficulty.Flow cytometry analysis showed that there was no significant difference in the size of trichomes cells and epidermal cells as well as the DNA content(2 C)of fruit in the RR and RRE,indicating that ploidy changes of cell chromosomes were not involved in the formation mechanism of trichomes.