Purple leaf basil plants express micronutrient deficiencies symptoms differently than green leaf basil plants

Abstract

All living organisms need essential nutrient elements to survive and thrive. For plants, of the 14 essential nutrient elements, over half show deficiency symptoms that include chlorosis. However, this is for plants with green leaves. For purple leaf basil, there has been no reported research on how microelement deficiency is expressed, diagnosed and/or corrected. The purpose of this research was to visually and quantitatively identify micronutrient element deficiencies, specifically, iron (Fe), manganese (Mn) and zinc (Zn), in ‘Red Rubin’, a purple leaf basil. To do this, three cultivars of basil, Italian Large Leaf, a green leaf basil; Aromatto, a mottled purple and green leaf basil; and Red Rubin, a purple leaf basil, were grown for 13–16 weeks. The experiment design was a split-plot with four treatments and the three cultivars. Data included visual observations, relative greenness (SPAD) measurements and tissue nutrient analysis. ‘Red Rubin’ leaves had similar SPAD values to both of the other cultivars. When Fe, Mn or Zn was deficient, purple pigment was lost. However, visual deficiencies such as yellowing and an increase in green color either veinally, interveinally or on the leaf margins varied. Based upon overlapping symptoms and based on tissue analysis, it is possible that there exists a 3-way or even 4-way interaction/balance among the minor elements Fe, Mn, Zn and possibly copper (Cu).