Effects Of Ca～(2+) On Some Physiological Metabolisms Of The Cucumber Under Cinnamic Acid Stress

Continuous cropping obstacles of cucumber (Cucumis sativus L.) could decrease yieldand quality seriously. Auto-toxic effect is one of the most important factors of cucumbercontinuous cropping obstacles. However, up to date, there is not report about the mechanismof Ca increasing the cucumber's ability of resistance to autotoxicity. In order to offer theorybasis on conquering cucumber continuous cropping obstacles, this article not only studied theeffects of Ca on the physiology metabolize of cucumber seed germination under auto-toxicmaterial (cinnamic acid, CA) stress from seed respiration, conductance rate,α-amylase andproteinase activity, the consumption rate of material, sugar, starch and protein, etc, but alsostudied the mechanism of Ca enhancing the resistance to autotoxicity of cucumber seedlingfrom active oxygen species(AOS) metabolism, the uptaking of nutrition, the content ofhormone . The main results are as follows.1 Effects of Ca on cucumber seed germination under CA stress1．1CA obviously restrained the cucumber seed germination, and the restraint degreeincreased with the concentration of CA increasing. Comparing with CK, germinatingenergies and rates of CA, CA, CA (the subscript number represents the mmol.Lconcentration of CA)were inhibited, except the germinating rate of CA was notsignificantly decreased, the germinating energies and rates of others were signifycantly orpositively significantly decreased.Ca soaking could relieve the inhibition of CA on seedgermination. Comparing with the same concentration CA treatments, applying Ca couldincrease germination energy and rate, except the germinating rate discrepancy betweenCA and CA+Ca(Ca represents soaking with Ca) was not significant, the others'discrepancies were significant or positively significant.1．2CA destroyed cucumber seed membrane structure and enhanced membrane permeability.The conductance rates of CA, CA, CA were positively significantly higher than thatof CK; It was seemed that the longer time of cucumber seed was treated by CA, the less inhi-bition on seed respiration. Ca soaking could variously relieve the destroy on membrane andthe inhibition on seed respiration under CA stress.1．3 CA inhibitedα-amylase and proteinase activity. Their activities decreased with the concentration of CA increasing. When treated with Ca, comparing with the same CAconcentration,α-amylase and proteinase activity were increased, their activities in thetreatments CA+Ca, CA+Ca and CA+Ca were significantly or positively significantlyimproved.1．4 Material metabolism was inhibited by CA. Comparing with CK, the consumption rates ofstarch and protein in treatments CA, CA, CA were positively significantly decreased,except the discrepancy of sugar consumption rate between CA and CK was not significant,the discrepancies between the other two CA treatments and CK were positivelysigmficant.Ca soaking could enhance the metabolizes of protein and starch in seedgermination stressed by CA, comparing with same concentration CA treatments ,theconsumption rate of protein was positively significantly increased, the consumption rates ofsugar and starch were variously increased.2 Effects of Ca on cucumber seedling growth under CA stress.2．1 The inhibition of cucumber seedling growth by CA was mainly on root. Root growthdecreased with the CA concentration increasing. CA decreased the fresh weight, the length oftaproot, the number of laterals and the root activity. Ca soaking could relieve the inhibitionon cucumber seedling growth stressed by CA. The improvement with Ca soaking oncucumber seedling growth and root activity was more obvious in the high CA concentration(≥0．5 mmol.L)treatments.2．2 Under CA stress, the amplitudes of O producing rate and HO content in cucumbercotyledon were higher than that of SOD and POD activity. Comparing with CK, the Oproducing rate in CA, CA, CA increased by 110．45%, 174．63%,361．94% respecttively,the HO content increased by 16．86%, 28．14%, 36．87% respectively, while the activity ofSOD and POD increased by 15．38%, 16．35% ,25．00% and 14．24%, 24．15%, 33．01%respectively. CA stress resulted in CAT activity decreasing, MDA content and membranepermeability increasing. Ca soaking could enhance the SOD and CAT activity of cucumberseedling under CA stress, decrease the O producing rate, HO content, MDA content andmembrane permeability, all these showed that Ca could relieve the damage made by activeoxygen under autotoxicity stress.2．3 Through impacting upon V and K, CA restrained the ability of cucumber seedling on uptaking nutrient (N0-N, HPO and K): the V of uptaking NO-N, HPO and Kwere decreased, the absorbing NO-N's K was increased. Ca treatment could relieve theinhibition by CA on uptaking NO-N, HPO and K of cucumber seedling, enhance theV on absorbing NO-N, HPO, K, while not significantly effect the K of K andHPO,and decrease absorbing NO-N 's K.2．4Comparing with CK, the treatment treated with 1．0 mmol.L CA , the auxin (IAA),mitogen (ZR),gibberellin(GA)and abscisic acid (ABA) content both in shoot and root werepositively significantly increased. Ca treatment adjusted the hormone content in cucumberseedling stressed by CA. Comparing with CA, in the treatment CA+Ca, IAA and ABAcontents in shoot were enhanced while ZR and GA contents were decreased; the four kindshormone contents in root were decreased.