Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: The level of acidity/alkalinity around apple root systems is a very important factor that determines the availability and mobility of nutrients for plant uptake. In this study, we evaluated the effect of acidity/alkalinity on root system development of apple rootstocks using an aeroponics system that was designed for this experiment. We evaluated root growth in three levels of acidity/alkalinity of four Geneva® apple rootstocks (G.210, G.214, G.41, G.890) under nutrient misting. New roots were allowed to grow for 30 days and then imaged using a high resolution camera. The images of developed roots were analyzed using the semi-automated GiA Roots® root architecture analysis software. We found that G.210 roots tended to grow flatter than G.890 roots. In addition, more alkaline solution was associated with increased root growth. Average root width tended to decrease with more alkaline values. We found very little influence on leaf nutrient concentrations of P, K, Ca, Mg, S, B, Zn, Cu, and Fe within the four rootstocks while , the level of acidity/alkalinity had a significant effect on P, Ca, and Mn. This research is the first of its kind investigating the effect of pH on root architecture in soil free (aeroponic) environment and may have implications for apple root behavior in field conditions where pH levels are different.

Technical Abstract: The pH level of the solution in the rhizosphere is a very important factor that determines the availability and mobility of nutrients for plant uptake. Solution pH may also affect root distribution and architecture of apple rootstocks. In this study, we evaluated the effect of solution pH on root system development of apple rootstocks using an aeroponics system that was designed and made at Cornell AgriTech Geneva, USA. Four Geneva® apple rootstocks (G.210, G.214, G.41, G.890) were grown in the aeroponic system under nutrient misting. The nutrient solution’s pH was adjusted to three pH values (5.5, 6.5 and 8.0). Root development was monitored for 30 days and evaluated regularly for distribution and root mass. Images of developed roots grown in the aeroponic system were collected at the end of the experiment using a high-resolution camera and analyzed using GiA Roots® software which generates root architecture parameter values in a semi-automated fashion. Resulting root architecture analysis showed that Geneva® rootstocks were significantly different for two architecture parameters. The length to width ratio analysis represented by two GiA Roots parameters (Minor to Major Ellipse Ratio and Network Width to Depth Ratio) showed that G.210 tended to flatter when compared to G.890 which tended to grow downward. Rootstocks G.214 and G.41 displayed similar growth values. The solution pH affected most root architecture parameter measurements where overall root growth was higher at pH 8 compared to pH 5.5 and 6.5 which showed similar growth. Average root width tended to decrease with higher pH values. While there were no significant differences in leaf nutrient concentrations of P, K, Ca, Mg, S, B, Zn, Cu, and Fe within the four rootstocks, the pH level of the solution had a significant effect on P, Ca, and Mn. This research is the first of its kind investigating the effect of pH on root architecture in soil free (aeroponic) environment and may have implications for apple root behavior in field conditions where pH levels are different.