Leaf Morphoanatomy and Biochemical Variation on Coffee Cultivars Under Drift Simulation of Glyphosate

ABSTRACT: The most widely used herbicide in coffee crop is glyphosate, it inhibits the biosynthesis of secondary metabolites, responsible for structures and substances of plant defense. This work aimed to evaluate the morphoanatomy, total phenols, flavonoids and caffeine in leaves of Arabica coffee submitted to different sub-doses of glyphosate. The treatments were combinations of three coffee cultivars (MGS Travessia, Oeiras MG 6851 and Catuaí IAC 144) and five sub-doses of glyphosate (0.0, 57.6, 115.2, 230.4 and 460.8 g a.e. ha-1). The total thickness of the leaf blade, thickness of adaxial and abaxial epidermis, palisade and spongy parenchyma, in addition to the total phenol, total flavonoids and caffeine were evaluated 30 days after spraying. Catuaí showed a reduction in the total leaf thickness, while the others cultivars had an increase. The thickness of adaxial and abaxial epidermis and palisade parenchyma was reduced, and the spongy parenchyma increased with increasing doses of glyphosate, regardless of the cultivars. There was an increase on the total phenols up to 115.2 g ha-1 glyphosate, and above this dose, the concentrations of phenols were reduced. The Travessia and Oeiras cultivars obtained a reduction of flavonoids up to 115.2 g ha-1; and above this dose, the concentration of flavonoids increased. The Catuaí cultivar showed an opposing behavior of the concentration of flavonoids. Oeiras and Catuaí showed a decrease of caffeine up to 115.2 g ha-1 and an increase at higher doses. Travessia showed an increase of caffeine in sub-doses above 115.2 g ha-1. The three cultivars showed a higher concentration of phenols in the palisade parenchyma after the application of glyphosate drift. Glyphosate reduces the thickness of the adaxial and abaxial epidermis and palisade parenchyma, and increases the thickness of spongy parenchyma. Doses of glyphosate above 230.4 g ha-1 result in the reduction of total phenols. The concentration of flavonoids and caffeine has varying effects with glyphosate application.

摘要：咖啡种植中应用最广泛的除草剂为草甘膦（glyphosate），其可抑制植物防御结构与防御物质合成所需的次生代谢物生物合成过程。本研究旨在评估经不同亚剂量（sub-doses）草甘膦处理后的阿拉比卡咖啡（Arabica coffee）叶片的形态解剖学（morphoanatomy）特征、总酚类物质（total phenols）、黄酮类化合物（flavonoids）及咖啡因（caffeine）含量。试验设置为3个咖啡品种（cultivars：MGS Travessia、Oeiras MG 6851与Catuaí IAC 144）与5个草甘膦亚剂量（0.0、57.6、115.2、230.4及460.8 g a.e. ha⁻¹）的完全组合。于喷施（spraying）后30天，测定叶片总厚度、上表皮（adaxial epidermis）与下表皮（abaxial epidermis）厚度、栅栏薄壁组织（palisade parenchyma）及海绵薄壁组织（spongy parenchyma）厚度，同时测定总酚类物质、总黄酮类化合物及咖啡因含量。
Catuaí品种的叶片总厚度出现下降，其余两个供试品种的叶片总厚度则有所上升。无论供试品种类型如何，随着草甘膦施用剂量升高，上下表皮厚度与栅栏薄壁组织厚度均呈降低趋势，而海绵薄壁组织厚度则随剂量升高而增加。总酚类物质含量随草甘膦剂量升高至115.2 g ha⁻¹时呈上升趋势，超过该剂量后酚类物质浓度逐渐降低。Travessia与Oeiras品种的黄酮类化合物含量在剂量达115.2 g ha⁻¹时呈下降趋势，超过该剂量后黄酮类化合物浓度则有所上升；而Catuaí品种的黄酮类化合物浓度变化趋势则与之相反。Oeiras与Catuaí品种的咖啡因含量在剂量达115.2 g ha⁻¹时出现下降，高剂量下则有所上升；Travessia品种在亚剂量高于115.2 g ha⁻¹时咖啡因含量持续升高。
经草甘膦喷施雾滴漂移（glyphosate drift）处理后，3个供试品种的栅栏薄壁组织中酚类物质浓度均有所升高。草甘膦可降低咖啡叶片上下表皮与栅栏薄壁组织厚度，并提升海绵薄壁组织厚度。当草甘膦剂量高于230.4 g ha⁻¹时，会导致叶片总酚类物质含量下降。黄酮类化合物与咖啡因浓度对草甘膦喷施的响应效应存在品种间差异。