Tipburn Severity and Calcium Distribution in Lisianthus (Eustoma Grandiflorum (Raf.) Shinn.) Cultivars under Different Relative Air Humidity Conditions

Abstract

Tipburn is a major problem for the production of lisianthus (Eustoma grandiflorum (Raf.) Shinn.) cultivars. Relative air humidity is regarded as a key environmental factor affecting tipburn severity in commercial crops. However, there are limited studies comparing the occurrence of tipburn and calcium (Ca) distribution in lisianthus cultivars under different relative air humidity conditions. Accordingly, we investigated the effect of relative air humidity on tipburn severity, transpiration rate, and Ca content in seven lisianthus cultivars. Under a high humidity treatment (70%), only two cultivars (“Voyage pink” (VP) and “Azuma-no-kaori” (AK)) showed significantly higher tipburn severity than those under a low humidity treatment (50%), which suggests that high humidity conditions do not always increase tipburn severity in lisianthus. Transpiration rates of all cultivars, except for AK, were either significantly lower under the high humidity treatment than under the low humidity treatment, or did not vary significantly between the treatments. In contrast, total Ca concentrations in all cultivars, except for “Piccolosa snow” (PS), were significantly higher under the high humidity treatment than under the low humidity treatment. These results suggest that Ca acquisition and distribution in lisianthus cultivars are strongly influenced by Ca uptake from root pressure.

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

“…, Tokyo, Japan): 0.4 mL/L) and its nutrient concentrations were same as that used in previous studies [17,18,26]. Five weeks after transfer to the phytotron, plugs were transplanted into 0.25 L polyethylene pots filled with Metro Mix 350.…”

“…Whole leaves were scored using an arbitrary tipburn severity index with ranking from 0 to 1 (0, asymptomatic; 0.2, deformed leaf margins; 0.5, leaf-tip chlorosis; 1, leaf-tip necrosis) [26]. The severity of tipburn in each plant was defined as Tipburn severity = {(severity index × leaf number)/whole leaves number per pot} × 100…”

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

“…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].…”

“…A previous study on 14 lisianthus cultivars indicated that tipburn-sensitive cultivars have a low ability to distribute Ca to the tips of upper leaves [10]. 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.…”