Study On Responsing Mechanism To Shading And High Temperature Stress In Pinellia Ternate (Thunb.) Breit

Pinellia ternate (thunb.) Breit. is herbaceous monocots of Aareeae Pnielll’a. It is one ofthe numeorus traditional Chinese l herbs，with its tubers used for medicine and there is ahigher requirement for it in recent years.Men has cultivated Pinellia ternate (thunb.) Breit.for30years.The growth of Pinellia ternate (thunb.) Breit. is greatly affected by cultivationconditions.In addition, the cost of cultivation is high and many diseases affect the tuber yieldof Pinellia ternate (thunb.) Breit. The research objects in the paper are Pinellias from threedifferent ecological production areas (Taizhou of Jiangsu, Weifang of Shandong, Anguo ofHebei), cultivated under the same environmental condition.Studies were taken that thePinellia’s physiological response to shading and high tempreture stress,and that the effect onmedicinal ingredients of Pinellia ternata Breit. tubers of shading conditions. Shading test setfour shading degrees, as follows:0%,30%,50%,70%, adjusting with different shade nets ofdifferent densities. The research materials were cultivated under the same environmental plots.High temperature test set four temperature treatments (day/night):25°C/20°C,30°C/20°C,35°C/20°C,40°C/20°C.The materials were planted in a seedling nursery andmoved into light incubato until the leaf unfolding for tempreture treatments.The main resultsare as follows:1.With the increasing of shading degree, the duration of sprout tumble of the Pinelliaternate (thunb.) Breit. become longer. The result was different in three P. ternata.s fromdifferent areas.The duration of P. ternata.from Shandong and Jiangsu was shorter,and the theduration of P. ternata.from Hebei was longer.Shade significantly reduced the total output of Pinellia, but it is conducive to thegeneration of Pinellia bulbils. With the increase of shade, the proportion of first level tuberwas significantly lower, fourth level tubers significantly increased.The output order of Pinelliafrom three sources was Shandong,Jiangsu,Hebei;and the difference was significant. Plantingin the same area continuously cause the degradation of the species. In order to avoidcuts,Breit in producing areas of the similar geographical environment should be selected forthe introduction.In0%-50%relatively light intensity conditions, the curve of leaf net photosynthetic dailyvariation of Pinellia ternata(Thunb.) Breit had two peaks and obvious phenomena of middaydepression.In70%relatively light intensity conditions, the diurnal net photosynthetic rate(NPR) exhibited a single peak curve to avoid phenomena of midday depression. Thegreater degree of shading，the maximum of diurnal net photosynthetic rate(NPR) was lowerwith time delay. Leaf total Pn/day and mean Pn/day of Pinellia ternata(Thunb.) Breit wassmaller with degree of shading increaseing. Pinellia ternate (Thunb.) Breit from three sourceshad the same result. With the growth of plant, the photosynthetic rate was lessening with thedegree of shading increasing.Shade could improve total chlorophyll content and the value of chlorophyll component.The greater degree of shading，photoinhibition had appeared in Pinellia ternate (Thunb.) Breitleaf. But this photoinhibition was reversible, the state of Chlorophyll fluorescence parametersrestored to its former good condition in the morning with reducing degree of shading aftermidday.Shading can reduce the content of soluble sugar and starch in leaves and tubers. And thekey enzyme’s activity also decreased along with the increase of shading degree. At the sametime, the synthesis of soluble sugar and the transport to the tubers would be restrained. So itreduced the starch content and influenced the yield.Shading reduced the SOD、POD and CAT enzymes’ activity of leaves and tubers. Therewas no significant difference in the treatments between the first sprout tumble and the secondtime. In the early time of the growth period, the air temperature and soil temperature werehigher. With the more shading degree leaves and tubers’ protection enzymes’ activity wouldincrease and the MDA content was lower. And in the later time of the growth period with themore shading degree the MDA content was higher.Shading increased the tuber’s total alkaloid content significantly, but the total alkaloidyield decreased along with the increase of shading degree. Alkaloid content and tuber’s sizehave negative correlation and its mechanism needs further research. Alkaloid yield in thethree places were the relationship that Shandong> Jiangsu> Hebei.2.High temperature stress significantly reduced the photosynthetic rate of Pinellia;withthe increase of temperature stress and the extension of time, leaf photosynthetic rate rapidlyreduced. High temperature reduced the content of chlorophyll, exacerbated the decompositionof chlorophyll, caused the light system damage irreversible, leaf senescence accelerating. Thehigh temperature significantly reduced the initial fluorescence,maximal fluorescence,maximum photochemical efficiency and PS Ⅱactual photochemical efficiency.Non-photochemical quenching increased significantly with temperatures rising and thendeclined with leaf senescence. High temperature stress destroyed protective enzyme system of the leaves and the tubers.The SOD and CAT enzymes’ activity in the leaves would increase at first and thensignificantly reduce with the increasing of the processing temperature and time but the PODenzyme’s activity continued to decrease. The protection enzymes’ activity of the tubers wouldincrease at first and then reduce with the increasing of the processing temperature and time.But the activity of the enzyme was reducing later in tubers than in leaves. MDA’s contentincreased significantly with the processing temperature and time. The increasing rate was lessin the early time than late. The there sources were all having this performance.High temperature significantly reduced the starch content in the Pinellia leaves andtubers.soluble sugar content increased first and then reduced significantly and SS, SPS, SSSactivity significantly reduced. High temperature stress reduces the accumulation ofassimilates, exacerbating their consumption, resulting in lower yields.