Growth Rhythm And Physiology Characteristic Of Parakmeria Yunanensis Seeding Under Different Tranceparences

Parakmeria yunnanensis fell into the third-ranking protection category of China, and it was widely used in city greening for the past few years, however, now the problems are lacking of germplasm resources and seedlings. The annual average temperature was 21.8℃ and such high temperatures keep on a long time every year in Nanning, but the suitable temperature for Parakmeria yunnanensis was 12.9℃-15.7 ℃, and there was no research on the shading of Parakmeria yunnanensis, so in this study we dealt with the Parakmeria yunnanensis seedlings in different transparence （100%NS、37.3%NS、17.9%NS and 7.1%NS）, and measured the parameters of the growth、physiology and photosynthesis, so we can analyse the relationship between different indicators and the light transmission, understand the effects and provide certain guidance for the seeding conservation, the results showed that:1.Under different transparences, the fastest growth rate of the seedlings’height and ground diameter happened in full exposure, the shading would restrain the growth of the Parakmeria yunnanensis obviously. With deeper shading, the absolute yield of seedling’s height、diameter and the relative growth rate would fall off. The increment of seedling’s height in full exposure respectively were 2.64 times of the 37.3%NS、3.14 times of the 17.9%NS and 4.56 times of the 7.1%NS; the increment of seedling’s ground diameter in full exposure respectively were 2.09 times of the 37.3%NS、3.14 times of the 17.9%NS and 4.00 times of the 7.1%NS;the sort of the single seedling’s biomass was the 100%NS> 37.3%NS> 17.9%NS> 7.1%NS,and the biomass of single seedling in full exposure was 1.46 times of the37.3%NS、1.91 times of the 17.9%NS and 2.35 times of the 7.1%NS.We found the seedlings of the Parakmeria yunnanensis were adaptable to the shade environment, they could even keep slowly growth under the 10%NS. The shading could influence the height deeper than the ground diameter, and affected the biomass of stems harder than the leaves. The remarkable fact was:37.3%NS could promote the growth of Parakmeria yunnanensis’roots.2.Under different transparences, the relative electrolytic leakage of Parakmeria yunnanensis showed a trend of decreased first and fell later, the maximum relative electrolytic leakage appeared in full exposure（17.32%）,and then went down to the minimum（2.59%） quickly in 37.3%NS; the contents of MDA ranked100%NS（17.75umol/g）>7.1%NS（17.63umol/g）>17.9%NS（17.20umol/g）>37. 3%NS（16.51umol/g）; the contents of soluble sugar ranked of:100%NS（0.41%）> 7.1%NS（0.29%）>17.9%NS（0.25%）>37.3%NS（0.24%）;the contents of free proline rankedof:100%NS（2549.79ug/g）>7.1%NS（2220.42ug/g）>17.9%NS（2095.39ug/g）> 37.3%NS（2026.83ug/g）;the activity of POD showed a trend decreased first and fell later, the sort was:37.3%NS（10.77u/（g·min））>100%NS（9.18u/（g·min））> 17.9%NS（8.34 u/（g·min））> 7.1%NS（7.74u/（g-min））;the activity of SOD ranked of:7.1%NS（302.55u/g）>100%NS（302.19u/g）>17.9%NS（301.41u/g）>37.3%NS（297. 18u/g）。3. Under different transparences, with the increasing degree of shade, the contents of chlorophyll a and chlorophyll b and their summation were all raised. In comparison to the situation of full exposure, the contents of chlorophyll a for the Parakmeria yunnanensis under 37.3%NS,17.9%NS and 7.1%NS respectively increased by 7.06%、43.53% and 54.12%, and at the same time the contents of the chlorophyll b respectively increased by 25.81%、64.52% and 100.00%; the Pn of the Parakmeria yunnanensis under 100%NS kept adding with the increase of the PAR, but the Pn of those seedlings under different transparences all increased to the greatest then began to drop. The rank of Pn was:17.9%NS(6.95 umolCO2m^-2s^-1)>100%NS(6.48 umolCO2CO2m^-2s^-1)>7.1%NS(5.67 umoCCO2m^-2s^-1)>> 37.3 %NS;the maximum Tr of different transparences appeared in different PAR:100 %NS (2000 umolm^-2s^-1),37.3 %NS(1000 umolm^-2s^-1),17.9 %NS(1000 umolm^-2s^-1)、7.1 %NS(1500 umolm^-2s^-1), and the greatest Tr were (2.24 mmolH₂Om^-2s^-1)、37.3%NS(1.54 mmolH₂Om^-2s^-1).17.9%NS (1.90 mmolH₂Om^-2s^-1)、7.1%NS (1.73 mmolH₂Om^-2s^-1); the Ci of those seedlings showed a trend of decreasing, all of the maximum appeared in the Oumolm^-2s^-1, the minimum Ci appeared in 2000umolm2s-1（204.93umolCO2mol-1） under the 100%NS、appeared in 1200umolm-2s1（212.28umolCO2mol-1） under the 37.3%NS、 appeared in 1000umolm^-2s^-1（143.14umoICO2mol-1） under the 17.9%NS and appeared in 800umolm^-2s^-1（236.40umolCO2mol-1） under the 7.1%NS; with the increased PAR, the Cond of those seedlings under the 100%NS kept increasing, the Cond under the 37.3%NS first added slowly and then dropped soon, and reached the minimum when the PAR was 2000umolm^-2s^-1,the Cond under 17.9%NS showed the similar rule but added fast after decreased slowly, the range ability of the Cond under 7.1%NS was the smallest, its maximum was 0.0673molH₂Om^-2s^-1 and the minimum was 0.0541 molH₂Om^-2s^-1.