In order to determine the optimal substrate combinations, and to provide scientific theories and technical guidance for container seedling nursery of tung tree seedlings with hypocotyle rootstocks.

Using yellow soil, peat, perlite, vermiculite, and coir as substrate raw materials, a total of 8 different substrate formulations were designed. The survival rate, growth traits, fruiting capacity, biomass, root indexes, root indicators, and photosynthetic properties were measured on the grafted seedlings of shoot anvil cultivated by different substrate formulations, and the quality of the grafted seedlings were comprehensively evaluated by combining the correlation analysis, principal component analysis and the value of the subordinate function.

1）The grafted seedlings cultivated with T1 (pure yellow soil) and T6 (60% yellow subsoil + 20% peat soil + 20% vermiculite) exhibited high graft survival rate and final survival rate, reaching over 87% and 74% respectively. In contrast, the T5 treatment (10% yellow soil +50% peat soil +20% vermiculite +20% perlite) had the lowest initial graft survival rate and final survival rate, which were only 71.11% and 57.78% respectively. This indicates that the substrate ratio treatments with higher yellow soil content yielded higher seedling initial graft survival rate and final survival rate compared to those with lower yellow soil content; 2) During seedling growth, the bud-seedling rootstock grafted seedlings of Vernicia fordii (tung oil tree) showed the best growth performance under the T6 substrate ratio. In the same year, their seedling height reached 27.31 cm, which was 98.47% and 99.49% higher than those of T7 and T8 respectively, with significant differences (P<0.05). The ground diameter was 10.06 mm, second only to that of T5. The total fresh weight was 34.03 g, which was 126.41% and 155.86% higher than those of T1 and T7 respectively, with significant differences (P<0.05). The total root length was 1 062.70 cm, which was 180.93% and 167.00% higher than those of T7 and T8 respectively, with significant differences (P<0.05); 3) Bud-seedling rootstock grafting technique enables flowering and fruiting of grafted seedlings in the following year. Among them, the grafted seedlings under T5 and T6 substrate ratios showed high fruiting rates, which were 26.47% and 23.33% respectively. The seedling height of fruiting branches under all substrate ratios was significantly lower than that of non-fruiting branches. Therefore, to achieve high yield in the 3rd year, it is recommended to prioritize removing fruits in the 2nd year after grafting; 4) A comprehensive analysis of 15 indicators (including seedling height, ground diameter, total fresh weight, total dry weight, total root length, root surface area, root diameter, root volume, chlorophyll a content, chlorophyll b content, etc.) was conducted using the entropy weight method. Among these, the T6 substrate ratio obtained the highest score of 1.007, followed by T2, T3, T4, and T5 substrate ratios (ranging from 0.425 to 0.531), while T7 had the lowest score of 0.111. The comprehensive scores of grafted seedlings under different substrate ratios ranked from highest to lowest as T6, T4, T5, T3, T2, T8, T1, T7.

The grafted tung tree seedlings with hypocotyle rootstocks grown in the T6 substrate mixture performed best and can be used as a suitable substrate for grafting and seedling cultivation in production.

This study investigated the effects of improved bark grafting on scion-rootstock healing, growth, and fruiting in low-yield Camellia oleifera forests after top-grafting, aiming to provide technical support for variety improvement.

Four cultivars (‘Huajin’, ‘Huaxin’, ‘Huashuo’, ‘Xianglin 210’) were grafted onto low-yield trees using modified bark grafting. Bud sprouting, wound healing, crown width, shoot length, basal diameter, and yield were monitored over three years.

1) Grafting in mid-June (vs. mid-May) accelerated bud sprouting, increased shoot height, and enhanced branching; 2) ‘Huajin’ and ‘Huashuo’ formed dense callus rings at graft unions by 60 days post-grafting, with wound healing observed in ‘Xianglin 210’ ‘Huajin’ and ‘Huashuo’ by day 75; 3) ‘Huajin’ exhibited superior branching, leaf expansion, and shoot growth in the first year; 4) After two years, graft unions tightened, callus expanded, and ‘Huajin’/‘Huaxin’ showed optimal healing; 5) Three-year-old ‘Huajin’ grafts achieved the largest basal diameter and tree height

The best time to perform high-grafting crown replacement on low-yielding Camellia oleifera forests using the improved bark-inlay grafting technique is mid-June. Grafting with ‘Hua Jin’ and ‘Hua Xin’ as scions shows good results in scion and rootstock healing. ‘Hua Jin’ has a significant advantage in the base diameter of new shoots and tree height growth. Grafting with ‘Hua Xin’ and ‘Hua Shuo’ as scions leads to a relatively higher increase in fruit yield in the first three years. The average fruit yield per tree of the four varieties after three years of grafting reached 8.2 kg, among which the fruit yield per tree of ‘Xiang Lin 210’, ‘Hua Xin’, and ‘Hua Shuo’ was all above 7.5 kg, and that of ‘Hua Jin’ was close to 7.5 kg.

This study investigated the response mechanism of tung tree seedlings to chromium stress, in order to provide technical support for the application of tung trees in repairing soil environment polluted by chromium.

A pot experiment was carried out by using the one-year-old tung tree seedlings as the materials, to study the application of different concentrations of Cr (0, 50, 100, 200 and 500 mg·kg^-1 soil) on the photosynthesis, chlorophyll (Chl) content, peroxidase (POD), superoxide dismutase(SOD), malondialdehyde (MDA) content, relative conductivity, stomatal width, leaf structure and chromium content of tung trees.

1) The result indicated that when the soil Cr³⁺ concentration was 50 mg·kg^-1, the growth of tung tree seedlings showed no significant difference in comparison with the control; 2) With a soil Cr³⁺ concentration of 100 mg·kg^-1, the net photosynthetic rate(P_n), chlorophyll (Chl) content, and soluble protein content of leaves were significantly reduced (P < 0.05); 3) When the soil Cr³⁺ concentration exceeded 200 mg·kg^-1, the photosynthesis of tung tree seedlings was significantly decreased (P < 0.05), the contents of MDA and SOD increased, and the stomatal width and the thickness of leaves was significantly reduced (P < 0.05); 4) After long-term chromium stress (60 d) of 500 mg·kg^-1 Cr³⁺, the photosynthetic system of tung tree seedlings was severely damaged. P_n decreased by 89.02% compared with the control, and the total chlorophyll content decreased by 24.35%. The MDA content increased by 47.18%, resulting in membrane lipid peroxidation, the relative conductivity increased by 1.43%, and the blade thickness decreased by 26.71% (P < 0.05); 5) The content of Cr³⁺ in each part of the tung tree seedlings increased with the increase in the chromium concentration of soil. The accumulation of Cr in the roots of tung tree seedlings was the highest, and the accumulation of Cr in the roots of the tung tree seedlings in the 5 treatment groups were 61.51, 22.30, 61.77, 64.18 and 38.25 times that of the leaves, respectively.

Taken together, tung tree seedlings can absorb chromium in soil when the chromium concentration does not exceed 100 mg·kg^-1 in soil, playing a role in remediating heavy metal soil.

Due to the immaturity of the asexual propagation technology system of tung tree, the seedlings are mainly produced by sowing seeds, which leads to the failure to maintain the excellent traits of the female parent. The study of the effects of different factors on the survival and growth of tung tree branches, and the most suitable grafting combination for tung tree grafting can provide a reference for improving the technical system of vegetative propagation of tung oil, and have certain theoretical and practical significance for the quality, efficiency and healthy development of tung oil industry.

The effects of grafting time, grafting method and scion type on the survival and growth of tung tree branches were investigated by using the current year-old semi-lignified bud stem segment of the ‘Huatong No. 1’ family as the scion, and the excellent single-plant seedlings of the Aleurites montana family were used as rootstocks.

The best grafting period was the summer solstice, and the highest survival rate was 91.67%, which was 10%, 10% and 4.77% higher than the highest survival rates of the beginning of spring, beginning of autumn and winter solstice, respectively, with no significant difference (P > 0.05), and 25.71%, 388.91%, 25.71% and 25.01% higher than the highest survival rates of spring equinox, beginning of summer, autumn equinox and beginning of winter, respectively (P < 0.05); The grafting method with the highest survival rate during the summer solstice was the splitting method, with a survival rate of 87.50%, which was 9.09% higher than that of the cutting method, and the difference was not significant (P > 0.05), but 33.32% higher than that of the joining method, and the difference was significant (P < 0.05). The best type of scion was apical bud at the beginning of spring, autumn equinox, beginning of winter and winter solstice, which was 940.63%, 113.61%, 899.74% and 323.85% higher than that of axillary bud grafted at the same period, respectively, with significant differences (P < 0.05). The best way to unwrap the film is to gently cut the grafted film on the side of the rootstock. The grafted seedlings at 8 stages were basically healed after 60 days of germination.

The best season for grafting is the summer solstice, and the scion type is axillary bud, although the grafting method with the highest survival rate is the splitting method, but considering the grafting cost and grafting efficiency, the suitable grafting method is the cutting method, and the cutting operation is simple, and more than 800 plants can be grafted per person per day, which provides a practical way for the asexual seedling breeding of improved varieties of tung tree.