Comparison of photosynthetic characteristics between the root tiller seedlings and grafted seedlings of Ziziphus jujube ‘Lingwuchangzao’

The objective of this study was to compare the differences in photosynthetic characteristics between root tiller seedlings and grafted seedlings of Ziziphus jujube ‘Lingwuchangzao’, to provide a theoretical basis and scientific support for the cultivation and selection of Lingwuchangzao with a high light efficiency, high quality and high yield.

In this study, the differences in leaf area, leaf nutrient content, relative chlorophyll content, transpiration rate, stomatal conductance, intercellular carbon dioxide concentration, net photosynthetic rate, water use efficiency, chlorophyll fluorescence parameters and so on were compared between root tiller seedlings and grafted seedlings of Lingwuchangzao. The results showed that the leaf area of the grafted seedlings was always larger than that of root tiller seedlings throughout the growth period, and the growth rate of leaf area was slightly different, but the overall trend was the same. The leaf nutrient content changed continuously throughout the growth period, the N content continued to decrease, and the P content of the root tiller seedlings reached the peak value of 6.82 g/kg in mid-July, which then decreased and subsequently increased slightly in late September. The P content of the grafted seedlings decreased continuously. The K content of both root tiller seedlings and grafted seedlings showed a trend of first increasing and then decreasing, both reaching the maximum values of 23.92 g/kg and 23.58 g/kg on August 10. In general, the contents of N and P in the grafted seedlings of Lingwuchangzao were higher than those in the root tiller seedlings, while the accumulation of K elements in the grafted seedlings was lower than that of the root tiller seedlings. In the whole growth period, the chlorophyll SPAD value of the root tiller seedlings was significantly higher than that of the grafted seedlings, reaching the peak value in mid-August, which was 12.88% higher than that of the grafted seedlings. The chlorophyll fluorescence parameters showed that the initial fluorescence of the root tiller seedlings of Lingwuchangzao was 12.35% lower than that of the grafted seedlings, while all the other parameters were higher than those of the grafted seedlings, among which the maximum light energy conversion rate Fv/Fm, potential light energy conversion rate of PSⅡ, the maximum fluorescence under light Fm' and the actual photochemical efficiency Y (Ⅱ) of PSⅡ showed significant differences.

The results of this study showed that the root tiller seedlings of Lingwuchangzao have higher light energy utilization and photosynthesis as well as greater high-yielding potential than the grafted seedlings, which can be used as the next key material for the selection and breeding of high-light efficiency, high-yielding and high-quality varieties of Lingwuchangzao.