Seasonal changes in photoprotective mechanisms of leaves from shaded and unshaded field-grown coffee (Coffea arabica L.) trees
Seasonal changes in photoprotective mechanisms of leaves from shaded and unshaded field-grown coffee (Coffea arabica L.) trees
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DOI：
10.1007/s00468-007-0190-7
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发表时间：
2008-06-01
影响因子：
2.3
通讯作者：
DaMatta, Fabio M.
中科院分区：
文献类型：
--
作者：
Chaves, Agnaldo R. M.;Ten-Caten, Angela;DaMatta, Fabio M.
咖啡原产于阴凉的环境，但通常在没有阴凉的情况下生长和产量更好。因此，可以推断，咖啡叶应该显示出足够的可塑性，以适应不同的光环境。然而，人们对咖啡中与这种可塑性相关的机制知之甚少。因此，这项工作的目的是探讨叶片光保护机制的差异。植物在田间生长并接受48%或100%的自然光。使用外部叶片从维科萨（巴西）的咖啡绿篱面向太阳的侧面在8月和10月，当生长和光合速率预计将分别是最小和最大的，并在12月，当这些变量的临时抑郁症是常见的。无论光照处理，咖啡叶表现出：（1）非常低的光合速率（通常低于2.5 μ mol m（-2）s（-1）），（2）慢性光抑制在8月（干燥，凉爽的季节），伴随着色素浓度的强烈损失，（3）离散，动态光抑制在10月和12月（雨季，温暖的季节）。与遮荫叶片相比，阳光照射下的叶片一般表现出较低的色素浓度，较低的电子传递量子产率，陡峭的倾角和相似的电子传递速率。总抗坏血酸池往往是较大的阳光照射比在阴影的叶子（但具有类似的氧化还原状态），而关键的抗氧化酶的活性，以及丙二醛积累和电解质渗漏，这些叶型之间是相似的。总体而言，咖啡树的光合机构表现出较低的表型可塑性变化的光照。
Coffee is native to shady environments, but often grows and yields better without shade. Thus, it may be reasoned that coffee leaves should display enough plasticity to acclimate themselves to contrasting light environments. However, little is known about mechanisms associated with such plasticity in coffee. This work aimed, therefore, to explore differences in leaf photoprotective mechanisms. Plants were grown in the field and received either 48 or 100% natural light. Evaluations were made using outer leaves from the sun-facing sides of the coffee hedgerow in Vicosa (Brazil) in August and October, when growth and photosynthetic rates are expected to be minimal and maximal, respectively, and in December, when temporary depressions in those variables are common. Regardless of light treatments, coffee leaves showed: (1) very low photosynthetic rates (generally below 2.5 mu mol m(-2) s(-1)), (2) chronic photoinhibition in August (dry, cool season) that was accompanied by strong loss of pigment concentration, and (3) discrete, dynamic photoinhibition in October and December (rainy, warm season). Compared with shaded leaves, sunlit leaves generally exhibited lower pigment concentration, lower quantum yield of electron transport, steeper inclinations and similar electron transport rate. Total ascorbate pool tended to be larger in sunlit than in shaded leaves (but with similar redox state), whereas activities of key antioxidant enzymes, as well as malondialdehyde accumulation and electrolyte leakage, were similar between those leaf types. As a whole, the photosynthetic apparatus of the coffee tree showed a low phenotypic plasticity to varying irradiance.