Tipburn Incidence and Ca Acquisition and Distribution in Lisianthus (Eustoma grandiflorum (Raf.) Shinn.) Cultivars under Different Ca Concentrations in Nutrient Solution

Abstract

Tipburn (calcium (Ca) deficiency disorder) is a major problem in the production of lisianthus cultivars. However, few studies have investigated the influence of different Ca concentrations in nutrient solution on tipburn incidence and Ca acquisition and distribution. Thus, it remains unclear why some cultivars exhibit tipburn under high Ca concentrations. To address this, we used three lisianthus cultivars ‘Azuma-no-Kaori’ (AK), ‘Celeb Wine’ (CW), and ‘Voyage Yellow’ (VY) and compared tipburn incidence and Ca acquisition and distribution under different Ca concentrations in a nutrient solution (low (40 ppm), moderate (80 ppm), and high (120 ppm) Ca). Tipburn severity and incidence in AK and VY significantly decreased with increasing nutritional Ca concentrations; the Ca concentrations in each organ and Ca acquisition competence (RGRCa) increased at higher nutritional Ca concentrations. In contrast, tipburn incidence in CW was 100% for all treatments. In CW, Ca acquisition competence and Ca concentrations in most organs increased with increasing nutritional Ca concentrations, but the Ca concentrations in the tips of the upper leaves did not differ significantly between treatments. Thus, our results suggest that the cause of tipburn under sufficient Ca conditions is an inability of the plant to distribute Ca to the tips of its upper leaves.

Excessive Calcium Accumulation in the Roots Is a Key Factor in Tipburn Incidence under High Ca Supply in Lisianthus (Eustoma grandiflorum) Cultivars

“…By contrast, RW was considered a tipburn-semi-sensitive cultivar, as the occurrence of tipburn could be prevented by supplying high concentrations of Ca in the nutrient solutions. This result was consistent with that reported in Azuma-no-kanori (AK) [13]. VP, in which the tipburn incidence was 100%, was considered a tipburn-sensitive cultivar.…”

“…In rice [16] and barley [17], it has been reported that a high K concentration inhibits Ca uptake. Therefore, a high content ratio of K in the nutrient solution in our previous experiments [10][11][12][13] may have prevented Ca acquisition and distribution in some lisianthus cultivars. It is necessary to investigate the relevance of Ca and K concentrations in lisianthus cultivars.…”

“…These cultivars were selected based on the results for tipburn severity (as high, medium, or low damage) reported previously [10]. Seedlings were developed and raised as previously reported [10][11][12][13].…”

“…Whole leaves were scored from 0 to 1 using an arbitrary tipburn severity index (0, asymptomatic; 0.2, deformed leaf margins; 0.5, leaf-tip chlorosis; 1, leaf-tip necrosis) [10][11][12][13]. Tipburn severity was determined using the following formula: tipburn severity = {(severity index × leaf number)/whole leaves number per pot} × 100…”

“…In addition, it has been suggested that the differences in the humidity and plant growth rate have negligible effects on tipburn incidence in the lisianthus cultivars [11,12]. A study on the responses of three cultivars to different concentrations of Ca supply has been reported [13], but there is no information on how Ca uptake and its distribution change before and after the onset of tipburn under high-Ca conditions. To determine the causes of the physiological disorder, it is necessary to investigate the changes in plants before and after the occurrence of tipburn.…”