Nutritional deficiency symptoms of young ‘cedro doce’ plants grown under macronutrient omission

ABSTRACT ‘Cedro doce’ [Pochota fendleri (Seem) Alverson & Duarte] is a native forest species in Amazon with great ecological and economic importance. Understanding nutritional requirements of the species allows cultivating Pochota fendleri with more efficient fertilization practices since its initial growth, as a seedling. Thus, this research aimed to evaluate the symptoms of nutritional deficiency of young ‘cedro doce’ plants. The experiment was carried out from September to December 2016, under greenhouse conditions, at Embrapa Roraima, in Boa Vista, RR, Brazil. The experiment was a randomized complete block design with seven treatments [complete solution and individual omission of the macronutrients (N, -P, -K, -Ca, -Mg, -S)] and three replications. Each experimental plot corresponded to a pot with one plant, corresponding to 21 plots. At 77 days after transplanting the seedlings to the pots, the plants were evaluated for symptoms of nutritional deficiency: total height, collar diameter, leaf number, chlorophyll a and b, chlorophyll a/b index ratio, shoot and root dry mass, and root/shoot ratio. The macronutrients omission caused nutritional deficiency symptoms in all ‘cedro doce’ plants. In general, P and N omission caused the least development of plants. This result is an indicative that ‘cedro doce’ is a high demanding species for both nutrients, especially phosphorus.摘要：‘甜雪松’（Cedro doce）[学名：Pochota fendleri (Seem) Alverson & Duarte]是亚马逊原生森林树种，兼具极高的生态与经济价值。明晰该物种的营养需求，可为其苗期高效施肥栽培提供科学支撑。本研究旨在评估幼龄甜雪松植株的营养缺素症状。本实验于2016年9月至12月在巴西罗赖马州博阿维斯塔市的Embrapa罗赖马研究中心温室环境中开展。实验采用完全随机区组设计，设置7个处理组：全素营养液组与单个大量元素缺素组（缺氮、缺磷、缺钾、缺钙、缺镁、缺硫），共3次重复。每个实验小区为定植1株植株的盆栽，总计21个实验小区。待幼苗移栽至盆中77天后，对植株的营养缺素相关指标进行测定，包括总株高、地径、叶片数、叶绿素a与叶绿素b含量、叶绿素a/b比值、地上部与地下部干重以及根冠比。结果显示，所有大量元素缺素处理均使甜雪松植株出现营养缺素症状。总体而言，缺磷与缺氮处理下植株生长发育状况最差，该结果表明甜雪松对这两种养分，尤其是磷素，具有较高的养分需求。