Effect Of Crop Development On The Emission Of Volatile From Tomato Leaf And Their Response To Oligosaccharide

A large variety of volatile organic compounds(VOCs)are synthesized by a range of physiological processes in many different plant tissues and themselves also extremely diverse(30 000 compounds),and include alkanes,alkenes,alcohols, aldehydes,ethers,esters and carboxylic acids.Most of them can be assigned to the following classes(in order of decreasing size):terpenoids,fatty acid derivatives including lipoxygenase pathway products,benzenoids and phenylpropanoids,and various nitrogen and sulfur containing compounds.Those low-molecular-weight volatiles that have different functional groups play a vital role in the plant life cycle by providing a way for plants to interact with the surrounding environment.Many factors could effects the quantity and quality of VOCs emitted from plants,including developmental stage,growth condition,and all sorts of stresses.Most of VOCs have the inhibited activity on microbe growth and are a part of plant chemical defense. Some of VOCs have the activity to enhance defense genes expression,and are an intercommunion signal molecular between plants themself or neighbor.In plant-microbe interaction,when older leaves/plants display increased resistance or reduced susceptibility to pathogens,this form of resistance often is referred to as age-related resistance(ARR).The onset of some ARR forms correlates with flowering,while others correlate with plant age,leaf size,or the synthesis of secondary metabolites or defense proteins.In this paper,we studied developmental-dependent variations of VOCs emission and their inhibitory activity to Botrytis cinerea and Fusarium oxysporum,and systemic acquire resistance(SAR)in tomato leaves in order to investigate the role of VOCs in plant ARR.The effects of crop development on the emission of volatile in tomato leaves and their antifungal activity towards chitosan oligosaccharide(CO)and Burdock fructooligosaccharide(BFO)were investigated.The ability of BFO to induce systemic acquire resistance(SAR)in tomato was studied.The cotyledons of cucumber were used to investigate the protection of Nd³⁺on plant against the oxidative stress,and the effects of Nd³⁺and La³⁺on physiological characters in respect of plant resistance.The mainly results are as followed:1.VOCs emitted from the leaves of tomato at different developmental stages(the two-,ten-leaf and anthesis periods)were collected by gas absorbing method and analyzed by GC/MS.The expressions of several key genes of the VOCs synthesis ways including lipoxygenase D(Lox D),phenylalanine transaminase 1(Pall)and 4-coumarate CoA ligase(4-CL)were investigated by SQ-PCR.The effects of VOCs emitted from tomato on B.cinerea and F.oxysporum were examined by a modified hanging drop methods.The resistances of tomato leaves at three developmental stages to B.cinerea in vitro were also studied.The results demonstrated that plant developmental stage variations in the levels and composition of VOCs emitted from leaves were notably.With plant developing,VOCs emitted from the leaves of tomato were significantly increased.In total 13,19,and 33 constituents were identified in VOCs emitted from leaves of tomatoes at two-,ten-leaf and anthesis periods, respectively.The amounts of VOCs emitted from ten-leaf and anthesis plants were 5.36 and 11.3 folds of those emitted from two-leaf plant,respectively.The expressions of LoxD,Pal1 and 4-CL,and the activities of LOX and PAL have a positive correlation with VOCs emitted from leaves of tomato at different developmental stages.The antifungal activities of VOCs emitted from leaves and the resistances of leaves to B.cinerea were enhanced with plant growth.2.Age-dependent variations of VOCs emission,its inhibitory activity,and resistance to B.cinerea in tomato leaves were investigated.The results demonstrated that volatile emitted from tomato decreased with leaf age(based on the leaf positions on the plant).Contents of VOCs decreased steadily with leaf age,from 452.4μg/g·Fw in young leaf to 146.6μg/g·Fw in old leaf.VOCs emitted from young leaf demonstrated the best antifungal activity on spores germination and hyphal growth against B.cinerea and F.oxysporum.The leaves of tomato become more susceptible to B.cinerea with age increasing.3.Several resistance related factors including isozyme,β-1,3-glucanase and chitinase activities in leaf of tomatoes at different development stages were analyzed. The results demonstrated that the isozymes of POD,SOD and EST in the same age leaves were enhanced with plant growth.Effects of leaf age on these isozymes were much lower than plant developmental stage.The activities ofβ-1,3-glucanase were enhanced significantly in anthesis plant,while chitinase were the highest of all in six-leaf plant.β-1,3-glucanase activities were enhaced with leaf age increasing,while chitinase activities were not significantly different in three age leaf.4.Developmental change in leaf volatile emission and several resistance factors in response to CO were studied.The results demonstrated that the leaves of tomato become less susceptible to oligosaccharide inducement with plant growth.The amount of VOCs and several mainly compounds emitted from leaves of two-leaf tomato decreased a little in 48 h,and then significantly increased after CO treatment. Although the total amount of VOCs emitted from the leaf of six-leaf tomato decreased a little,the kinds of VOCs were markedly increased by CO elicited.The amount of VOCs emitted from anthesis plant decreased significantly.After CO treatment.LOX andβ-1,3-glucanase activities in two-leaf plant were significantly enhanced,and become more susceptible than six-leaf and anthesis plants.Chitinase activities were markedly increased in leaves of six-leaf and anthesis plants at 72 h after CO treatment. There were no significantly changes in leaf of two-leaf plant after CO treatment.5.To investigate the influence of leaf age(based on the leaf positions on the plant) on volatile emissions and leaf resistance response to elicitation,the anthesis tomatoes were treated with CO.The results demonstrated that the leaves of tomato become more susceptible to CO with age increasing.The responses of young leaf to CO treatment that were attenuated or delayed included the quantity and quality of VOCs. VOCs released from old and adult leaves were dramatically increased after treatment with CO.In contrast,VOCs emitted from young leaf was decreased to 88.4%of the control at 72 h after CO treated.Resistances of leaves at three ages to B.cinerea were all enhanced by CO treated.There were an increase of 33.1%,39.4%and 34.2%in the resistance of young,adult and old leaf compared to the control group.6.The effects of plant development on the VOCs emission and defense-related enzymes response to BFO were studied.The results demonstrated that the response of tomato leaf to BFO depended on the plant developmental stages.VOCs emitted from six-leaf plant response to BFO were increased,and detected fifteen new compounds. The amounts of VOCs,aromatic compounds,monoterpene and sesquiterpenoids emitted from leaf of six-leaf plant were enhanced markedly after BFO elicited.For BFO treatment,VOCs emitted from leaf of two-leaf plant were significantly enhanced and 138.8%higher than the control.After BFO treatment,VOCs emitted from anthesis plant changes greatly in quantity and total amount of VOCs decreased sharply.The amount of oxygenated aliphatic compounds and sesquiterpenoids emitted from anthesis plant were significantly decreased,but the amounts of aromatic compounds and monoterpene were markedly enhanced after BFO treated.β-1,3-glucanase activity in two-leaf plant was notbly enhanced by BFO treatment. Chitinase activity response to BFO was enhanced with plant growth. 7.To investigate the influence of leaf age on volatile emissions and their antifungal activity of VOCs,defense-related factors and leaf eliciting resistance,the anthesis plant leaf were treated with Burdock fructooligosaccharide.The results demonstrated that the leaf of tomato become more susceptible to BFO with leaf age increasing.After BFO treatment,the synthesis and release were attenuated or delayed in young leaf in terms of the quality and quantity of VOCs.VOCs emitted from young leaf were significantly reduced after BFO treated.After BFO treatment,the amount of oxygenated aliphatic compounds and aromatic compounds were significantly enhanced,but there were no significantly different in the amount of monoterpene and sesquiterpenoids different in adult leaf.VOCs emitted from old leaf were markedly enhanced after BFO elicited,especially in the content of monoterpene.The inhibitory activity of volatile emitted from adult and old leaves increased significantly against two fungi after BFO,while VOCs emitted from young leaf were not changes.After BFO treatment the generation rate of O₂^-·become more susceptible in tomato leaf with leaf age increasing.The changes ofβ-1,3-glucanase activity were similar in three leaf age,while the increase in young leaf were the most in three leaf ages after BFO treatment.For BFO treatment,chitinase activity was enhanced significantly in adult leaf,and a little in old leaf.The isozymes of POD and SOD were markedly enhanced by BFO eliciting in young leaf,and were increased in adult leaf after BFO treated.For BFO elicited,resistances of leaves at three ages to B.cinerea were all enhanced.An increase of resistance in old leaf was higher to BFO than adult and young leaves.8.We studied the ability of BFO to induce SAR in tomato.It is revealed that after BFO eliciting,level of SA and SAG in the first leaf sprayed with BFO and the untreated leaf of the same seedling increased sharply.The changes of SA and SAG in untreated leaf were lower than this change in local leaf after BFO treatment.BFO treatment enhanced markedly the expressions of PR2,Chit,LoxD,and Pal1 in local leaf,and PR2,Chit,and in systemic leaf Pal1 expression also increased significantly. In addition,the generation rate of O₂^-·reached the highest at 3h in local leaf and 12h in systemic leaf,and the extent of oxygen burst in systemic leaf was much lower than this in local leaf.β-1,3-glucanase and chitinase activities significantly increased both in the first leaf treated with BFO and in systemic leaf.9.The protection of Nd³⁺on the cotyledons of cucumber against the oxidative stress by H₂O₂ was studied.The result revealed that both Nd³⁺pretreatments and Nd³⁺treated with H₂O₂ synchronous decreased the injury of H₂O₂ effectively.The permeability of cell membrane,the generation rate of O₂^-·and the content of MDA were obviously lower than that of H₂O₂ treatment.The cucumber cotyledons were sprayed with Nd³⁺ and La³⁺,and the changes on SA and SAG contents,the generation rate of O₂^-·,and the activities ofβ-1,3-glucanase and chitinase were measured.The results demonstrated that the yields of endogenous SA and SAG in cucumber cotyledons were enhanced significantly in a short time in response to Nd³⁺and La³⁺treatments. The generation rate of O₂^-·increased gradually after Nd³⁺or La³⁺treatments,and then decreased in cucumber at 12 h.β-1,3-glucanase and chitinase activities were significantly enhaced by Nd³⁺and La³⁺treatments.In summary,the emission of VOCs,some defense related factors,and the resistance to pathogen of tomato leaf were affected by plant developmental stage and leaf age. Most compounds of VOCs have the inhibitory microbe growth activity and play a key role in plant chemical defense.Thus,VOCs emitted from tomato leaf play a role in plant age-related resistance.VOCs emission,several PR genes expression and PR activities of tomato leaf in response to oligosaccharide elicit varied with plant developmental stage and leaf age.Studies of these forms of resistance may help us to evaluate more exhaustively the plethora of levels of regulation during development, the variability of the defense potential of developing hosts and may have practical application,making it possible to reduce pesticide applications.Furthmore,we also confirmed that BFO may induce the SAR response through an SA dependent signal pathway to enhance defense related genes expression and improve PR enzymes activities.Due to the low cost and abundant supply of substandard Arctium lappa roots,we believed that the activation of plant defenses using the BFO elicitor could be a valuable tool that would contribute to a new alternative strategy for developing plant protection.Rare earth(RE),a kind of natural mineral,has been used as the beneficial elements to enhance crops resistance to abiotic and biotic stress for quite a long time. The mechanism about RE biological activities is not clear yet.In this paper,these results suggest that RE can enhance the resistance of plant to stress factors and diseases due to directly decrease the injury of free radical to plant and through the signal pathway of salicylic acid.