| Pinellia tematat (Thunb.) Breit is a perennial herb plant belongs to Pinellia tenore of Araceae. It is one of the important Chinese traditional medicine and used as herbal pieces. P. tematat can be harmed by high temperature in summer. High temperature cause the part of the ground easily withered, which are commonly known as "sprout tumble". This phenomenon affects its yield and contents of effective constituents seriously. Therefore, it is an urgent need to solve the problems which improves the production and thermotolerance of P. ternatat currently.Calcium is not only a major necessary element which is needed for the growth and development of plants but also a second messenger which involved in responding to outside environment. Researches had shown that spraying exogenous calcium can delay sprout of P. ternatat and increase its production.In order to clarify the process of signal transduction which calcium involves and the protective effect of exogenous calcium on P. tematat under high temperature stress. In this study, P. ternatat as plant material, effects of different concentration of calcium ion on photosynthesis and chlorophyll fluorescence of P. tematat were studied under high temperature stress. Effects of pretreatments with Ca2+ inhibitors and CaM antagonist on calcium fluorescence intensity, protein kinase activity and antioxidant enzyme activity were also studied. The growth of seedlings and accumulation of effective constituents were studied under heat stress. And the optimal calcium concentration was found out. The results as follows:1. The result showed that contents of chlorophyll a, b, a+b and ratio of chlorophyll a/b were relatively higher by spaying Ca2+ in heat stress. Compared with the control, spaying 6 mmol ·L-1 Ca2+ significantly enhanced the net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal limitation (Ls), but reduced intercellular CO2 concentration(Ci) in P. Ternata leaves. With the increase of Ca2+ concentration, maximal PSII efficiency (Fv/Fm), actual photo synthetic efficiency (Yield) and photochemical quenching coefficient (qP) initially increased and then decreased, however, minimal fluorescence (Fo) and non-photochemical quenching coefficient (NPQ) went down first and then went up. With the treatment of calcium ion, the inhibition of photosynthesis and the damage of PSII system were relieved under heat stress.2. Calcium fluorescence intensity in leaves of P. ternatat were improved by heat (37℃) and exogenous calcium, and reached the maximum in 4 hour in this experiment. P. ternatat treated by exogenous calcium and different calcium messengers showed that exogenous calcium increased Heat-induced calcium fluorescence intensity significantly but the increase of Heat-induced calcium ion concentration were inhibited by calcium chelator EGTA, calcium channels inhibitor LaCl3, CaM antagonist TFP and mitogen-activated protein kinases (MAPK) activity inhibitor PD98059 significantly. It suggested that heat-induced calcium ion concentration increases mainly came from the internal flow of extracellular Ca2+ possible in P. ternatat leaves, and MAPK was also involved in this process.3. Heat stress led to significant increases in the activity of protein kinase, but PD98059 inhibited Heat-induced protein kinase activity. Compared with heat treatment, exogenous calcium activated protein kinase activity significantly, EGTA, LaCl3 and TFP treatment inhibited heat-induced protein kinase activity highly. It showed Ca2+ was involved in heat-induced MAPK activity.4. Heat stress induced significant increases in the activities of the antioxidant enzymes SOD, POD, APX. Pretreatment with CaCl2 resulted in remarkable increases in the activities of Heat-induced SOD, POD, CAT, APX. But SOD, POD and CAT activities were inhibited by LaCh, EGTA, TFP significantly. These results indicated that Heat-induced the activities of antioxidant enzymes were Ca2+-dependent. Activities of heat-induced SOD, POD, APX were decreased by PD98059, which indicated that MAPK may participate in heat-induced antioxidant protection.5. Our result showed that dry mass of roots, stems, leaf and tubers and total biomass by spaying 2 to 6 mmol·L-1 Ca2+ were higher than the control, and plant high and stem diameter were relatively higher by spaying Ca2+. Compared with the control, dry mass and fresh mass of tubers were significantly increased by Ca2+ treatment. And the most mass of tubers were applied by 2 mmol·L-1 Ca2+. With the increase of Ca2+ concentration, contents of guanosine, adenosin and total alkaloids initially increased and then decreased in general, yield of theirs and polysaccharide tended to went up first and then went down similarly. The applications of medium concentration of exogenous Ca2+ was conducive to promote the growth of Pinellia temate, improved contents of effective constituents and yield of Pinellia temate tubers significantly. |
PDF Full Text Request