Leaf anatomy and morpho-physiological mechanisms of acclimation to high irradiance in heliconia genotypes

ABSTRACT The amount of solar irradiation available in the growing environment can cause significant changes in physiology and leaf anatomy that enable crops to acclimate to different light conditions. In this sense, the objective was to characterize the leaf anatomy and to elucidate the morpho-physiological mechanisms of acclimation to high solar irradiance of heliconia genotypes during the initial stage of development under semiarid conditions. The experiment was conducted in the municipality of Petrolina, Pernambuco state, Brazil (09° 19’ 14” S, 40° 32’ 40” W, and 387 m of altitude) and the behavior of three heliconia genotypes (Heliconia rauliniana; H. bihai cv. Lobster Claw Two, and H. rostrata) grown in full sun and shading (50%) environments were evaluated. At 30 days after the implementation of the experiment, leaf anatomy, chlorophyll index, plant height, number of leaves, and number of tillers were analyzed. Heliconia leaves are characterized as amphistomatous with tetracytic stomata. In its main vein there are aerenchyma structures and hypodermis on the abaxial and adaxial sides. The responses to different light conditions in plants of H. bihai, H. rauliniana, and H. rostrata are genotype-specific. Furthermore, the anatomical structures and physiological changes observed in H. bihai and H. rauliniana plants demonstrate that these genotypes present greater plasticity and consequently greater potential for acclimation to high solar irradiation conditions. Thus, the genotypes H. rauliniana and H. bihai emerge as a potential alternative for cultivation in gardens or in open areas and for exploration as cut flower in regions with high solar irradiation availability.

摘要
生长环境中的太阳辐射量可显著改变作物的生理特性与叶片解剖结构，使其能够适应不同光照条件。基于此，本研究旨在对半干旱条件下生长初期的蝎尾蕉（Heliconia）基因型进行叶片解剖结构表征，并阐明其适应高太阳辐射的形态生理机制。
本试验于巴西伯南布哥州佩特罗利纳市（南纬09°19′14″，西经40°32′40″，海拔387米）开展，评估了3种蝎尾蕉基因型——雷氏蝎尾蕉（Heliconia rauliniana）、比亥蝎尾蕉栽培变种‘龙虾爪二号’（H. bihai cv. Lobster Claw Two）以及喙状蝎尾蕉（H. rostrata）——在全光照与50%遮阴环境下的生长表现。试验实施30天后，对叶片解剖结构、叶绿素指数、株高、叶片数及分蘖数进行了测定分析。
蝎尾蕉叶片为上下表皮均分布气孔的两面气孔型，气孔类型为四胞型（tetracytic stomata）。其主脉的远轴面与近轴面均具有通气组织（aerenchyma）与下皮组织（hypodermis）。
比亥蝎尾蕉、雷氏蝎尾蕉与喙状蝎尾蕉对不同光照条件的响应均具有基因型特异性。此外，在比亥蝎尾蕉与雷氏蝎尾蕉植株中观测到的解剖结构与生理变化表明，这两种基因型具有更高的表型可塑性，因此具备更强的高太阳辐射环境适应潜力。综上，雷氏蝎尾蕉与比亥蝎尾蕉可作为高太阳辐射区域园林露地栽培或切花生产的潜在优选品种。