Grafting alleviates potassium stress and improves growth in tobacco

Abstract

Background Potassium is a nutrient element necessary for tobacco growth. Tobacco leaves with high potassium content are elastic and tough, rich in oil. And the same time, potassium can also improve the scent and aromatic value of flue-cured tobacco by regulating the synthesis of aromatic hydrocarbons in leaves.. It is an important quality indicator for flue-cured tobacco. However, the potassium concentration in tobacco leaves in most areas of China is generally lower than the global standard for high quality tobacco. Two tobacco genotypes were grafted to each other under different potassium levels to test whether potassium content and plant growth can be improved by grafting in tobacco. Results The growth of tobacco in all treatments was inhibited under potassium starvation, and grafting significantly alleviated this potassium stress in ‘Yunyan 87’. The trends in whole plant K + uptake and K + transfer efficiency to the leaves corresponded to the growth results of the different grafts. The nutrient depletion test results showed that the roots of ‘Wufeng No.2’ had higher K + absorption potential, K + affinity, and K + inward flow rate. K + enrichment circles appeared at the endoderm of the root section in the energy dispersive X-ray figure, indicating that the formation of Casparian strips may be partly responsible for the lower rate of lateral movement of K + in the roots of ‘Yunyan 87’. Gene expression analysis suggested that energy redistribution at the whole plant level might constitute one strategy for coping with potassium starvation. The feedback regulation effects between scion ‘Wufeng No.2’ and rootstock ‘Yunyan 87’ indicated that the transmission of certain signaling substances had occurred during grafting. Conclusions ‘Wufeng No.2’ tobacco rootstock grafting can increase the K + uptake and transport efficiency of ‘Yunyan 87’ and enhance plant growth under potassium stress. The physiological mechanism of the improved performance of grafted tobacco is related to higher K + uptake and utilization ability, improved xylem K + loading capacity, and up-regulated expression of genes related to energy supply systems.

Response of grafting tobacco to low potassium stress

“…NKT1 is an inwardly rectifying K + channel gene that mediates K + uptake in Shakerlike family expressed in tobacco cells [30]. In our previous studies, it was found that low potassium levels can induce down-regulation expression of this gene [19]. This corresponds to the results of this experiment.…”

“…Regardless of whether there was normal K supply or K starvation, the K content of the plants with the W genotype tobacco rootstock was significantly higher than the plants with the Y genotype. Combined with our previous research [19], grafting not only improved tobacco growth, but also increased the whole-plant K content of the Y genotype tobacco compared with the nongrafted original variety. Another interesting observation in the experiment was that the distribution of K + in the tobacco plant changed under K starvation.…”

“…Therefore, to provide insight into the signaling pathway of grafted tobacco in response to low potassium stress, the co-expression analysis of differentially expressed genes and differentially accumulated metabolites in grafted tobacco will be our next work need to do.. transplanted the plants into hydroponic box, with 12 seedlings planted per container. The nutrient solution for hydroponics was formulated as previous study [19]. Air pumps were adopted to supply oxygen to each container through a hose for oxygen supply to the tobacco seedlings during experiment.…”

“…In the previous study [19], we investigated the alleviation effect of grafting on potassium uptake in roots and tobacco growth inhibition under low potassium stress. However, the effect of grafting on the low potassium stress perception and coping mechanism of tobacco at the whole plant level is not clear.…”

Grafting Tobacco onto Nutrient-efficient Rootstocks Improves Photosynthesis

“…According to our previous studies, grafting affects the absorption and utilization of K 1 in tobacco, especially that of a series of strategies for coping with low potassium stress, and also changes the circulation and redistribution pattern of K 1 in tobacco plants (Hu et al, 2019). This will have a significant impact on the photosynthesis of the tobacco leaves and will directly change the synthesis and transportation of assimilation products.…”