Root Architecture, Leaf Nutrient Levels and Photosynthesis of Columnar and Standard Apple Seedlings are Different

Abstract

The columnar apple tree is a valuable apple breeding resource, which differs from the standard apple tree in tree architecture. In this study, we used two-year-old F ₁seedlings of columnar and standard apple trees to study their differences in root architectures, nutrient uptake and photosynthesis. The results showed that 1) the numbers of root tips, forks and crossings of the columnar trees were significantly higher than those of the standard trees; 2) F ₁progenies of columnar genotypes had more average root tip numbers, total root lengths and root volumes than those of the two standard genotypes; 3) leaves of the columnar trees had significantly higher (1.77-2.34-fold) Ca, Mg, Fe, Zn and Cu concentrations than the leaves of standard trees, and macronutrient K concentration for standard trees was higher (1.03-1.1-fold) than for columnar trees; 4) leaves of the columnar trees had significantly higher chlorophyll a, chlorophyll b and chlorophyll a+b concentrations; 5) diurnal variations of both net photosynthetic rate (Pn) and transpiration rate (Tr) showed bimodal curves with a "siesta" phenomenon, and Pn and Tr of the two columnar genotypes were higher than those of the standard trees.