| Dwarf culture and compact planting of apple has become a development trend of modern apple production due to its earlier bearing and high yield, good quality and facilitated mechanization management. One of the main ways to achieve dwarf and compact planting cultivation was breeding and utilizing dwarf rootstocks. In this reasearch, the tetraploid SH40 which obtained by artificial induction was used as materials, and diploid SH40 as the control, to study its morphological, photosynthetic characteristics, enzyme activity,endogenous hormone content and its effect on scion varieties, which would provide a new approach to the breeding of apple rootstocks. The main results were as follows:1. Ploidy variation leaded to the decreased growth of plants. The plant height, stem diameter, the length of internode and petiole of tetraploid SH40 were 89.75%, 91.80%,88.89% and 91.6% of the diploid respectively. The lenticel density, stomatal density,catheter density and the proportion of catheter total area in xylem of tetraploid SH40 were 42.29%,38.29%,68.75% and 86.61% of the diploid respectively. Meanwhile the leaves index decreased; while the leaf thickness, lenticel size, stomata length and width and branch-cortex ratio increased, which were 1.18, 1.91,1.34,1.26 and 1.14 times of the diploid respectively.2. The chlorophyll a, chlorophyll b, total chlorophyll and chlorophyll a/b ratio of tetraploid SH40 leaves were less than the diploid significantly. The diurnal variation of photosynthesis of tetraploid SH40 was unimodal curve, which had no "midday depression", and the net photosynthetic rate at 12:00 was 18.40% higher than the diploid.Meanwhile,the diploid was bimodal curve, and the peak appeared at 10:00am and14:00pm; Besides,the net photosynthetic rates of tetraploid SH40 were 41.95%, 62%higher than the diploid at 6:00 and 18:00; the light saturation point and light compensation points of tetraploid SH40 reduced to 87.26% and 94.55% of the diploid respectively. Apparent quantum efficiency increased to 1.18 times of the diploid. The units area absorption of light(ABS/CSO), units area capture of light(TRO/CSO), units area of hot dissipation(DIO/CSO) and the reaction center of density(RC/CSO) of tetraploid SH40 were higher than the diploid significantly, which were 1.05,1.02,1.21 and 1.16 times of the diploid respectively. However, the units area electronic passed of quantum produced amount(ETO/CSO) had no significant differences to the diploid;and the maximum light chemical efficiency(φPo) and quantum yield for electron delivery(φEo) of the tetraploid were less than the diploid. Meanwhile, the quantum ratio for heat dissipation(φDo) of the tetraploid was higher than the diploid significantly; and the photochemical property index(PIABS) of the tetraploid was less than the diploid.3. The average contents of the IAA and ZR in the tetraploid were less than that of the diploid, while the ABA content was more than the diploid, GA3 content did not differ significantly, IAA/ABA, and GA3/ABA, ZR/ABA and(IAA+GA3+ZR)/ABA ratio were less than the diploid, coinciding with its dwarfism.4. The activities of IOD, POD, PAL and SOD in tetraploid SH40 leaves were significantly higher than the diploid control both on May 25 and October 15.5. The contents of boron in leaves had no significant difference between the tetraploid and the diploid SH40. The contents of Mg, Fe and Mn in tetraploid SH40 leaves decreased to 87.48%, 80.44% and 60.22% of the diploid respectively. While the contents of P, K, Ca, Cu and Zn increased to 1.10, 1.45, 1.10, 1.11 and 1.16 times of the diploid.6. The semilethal temperature of tertraploid SH40 and the diploid before the frost hardening were-29.37℃ and-33.46℃ respectively by conductivity method, while after the frost hardening they decreased to-32.10℃ and-37.70℃ separately,cold resistance decreased compared with the diploid. The contents of soluble sugar, soluble protein and proline associated with winter resistance declined in tetraploid, consistent with changes in cold hardiness. After the inoculation of physalospora piricola nose in the field, the morbidity of tetraploid was 8.23%, lower than the diploid. Disease index was 70.57% of the control, the resistance ability of SH40 to physalosporais enhanced significantly compared with the diploid.7. The affinity of tetraploid SH40 with the main cultivars had no significant difference with that of the diploid, and the survival rates of the Tianhong No.2, Gala, and Ryoka grafted on tetraploid SH40 interstock were 92.0%, 92.7% and 92.3%, and the diploid were 94.3%, 95.0% and 95.3% respectively. The affinity of tetraploid SH40 with Robusta was lower than diploid, and the grafting survival rate was 82.7% on average, while the diploid was 92.3%, which had a significant difference.8. The growth of Tianhong No.2 and Gala which grafted on the interstock of tetraploid SH40 were reduced. The height, roughness and internode length of Tianhong No.2 grafted on tetraploid SH40 were 87.88%, 80.93% and 93.55% of diploid respectively; while these indexes of Gala grafted on tetraploid SH40 were 88.24%, and91.42% and 91.18% of diploid respectively.9. The results indicated that the chlorophyll a, chlorophyll b and tatal chlorophyll contents of Tianhong No.2 grafted on the tetraploid SH40 interstock were more than those on the diploid, but the value of chlorophyll a/b had no significant differences; thediurnal variation of photosynthesis of Tianhong No.2 grafted on tetraploid or diploid SH40 interstock were both unimodal curves.The net photosynthetic ratios of Tianhong No.2 on tetraploid SH40 were less than that on the diploid between 7:00 am and 11:00am, but higher than that on the diploid combination after11:00. Meanwhile tetraploid combination showed no " midday depression ", while the diploid combination declined apparently after 12:00 in photosynthetic rate.Chlorophyll fluorescent parameter ABS/CSO and TRO/CSO of Tianhong No.2 on tetraploid SH40 interstock were higher than those on the diploid, DIO/CSO and φDo from 6:00 to 13:00 were higher than those on the diploid, while between 13:00 and 18:00 were less than those on the diploid; theφPo、ψO、φEo and PIABS of Tianhong No.2 on tetraploid SH40 interstock were less than those on the diploid from 6:00 am to 13:00 pm, but more than those on the diploid from13:00 pm to 18:00 pm.10. The activities of IOD, POD and PAL in Fuji and Gala leaves grafted on tetraploid SH40 were significantly greater than the diploid control both on May 25 and October 15, but PPO enzyme had no significant difference.11. The IAA and GA3 contents of both Fuji and Gala on tetraploid SH40 interstock were less than that of the diploid, but the ABA content was more than that of diploid, ZR content did not differ significantly both on May 25 and October 15. The value of IAA/ABA, GA3/ABA, and(IAA+GA3+ZR)/ABA in above two cultivars on tetraploid SH40 were less than that of the diploid.12. For Tianhong No.2 and Gala grafted on tetraploid SH40 interstock, the Mn content in leaves declined to 79.3% and 78.7% of those on the diploid control. But for Tianhong No.2 grafted on tetraploid SH40 interstock, the contents of P, K, Ca, Mg, Fe, B,Cu and Zn were 1.13, 1.22, 1.26, 1.28, 1.05, 1.70, 1.12, 1.47 and 1.83 times of those on the diploid, respectively; for Gala apple, the contents of mentioned nutrition elements were 1.21, 1.06, 1.32, 1.03, 1.16, 1.47, 1.32, 1.25 and 1.42 times of those on the diploid. |
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