Tattini M, Gravano E, Pinelli P, Mulinacci N, Romani A
1 Istituto sulla Propagazione delle Specie Legnose - Consiglio Nazionale delle Ricerche, Via Ponte di Formicola 76, I-50018 Scandicci, Florence, Italy.
New Phytol. 2000 Oct;148(1):69-77. doi: 10.1046/j.1469-8137.2000.00743.x.
Experiments were conducted on Phillyrea latifolia plants grown under a dense overstorey of Pinus pinea (shade plants) or on seashore dunes (sun plants) in a coastal area of Tuscany (42° 46' N, 10° 53' E). Total integrated photon flux densities averaged 1.67 and 61.4 m mol m d for shade and sun sites, respectively. A leaf morphological-structural analysis, a qualitative and quantitative analysis of phenylpropanoids of leaf tissue and leaf surface, and a histochemical localization of flavonoids were conducted. The area of sun leaves reached 57% of that of shade leaves, whereas leaf angle (β), sclerophylly index (ratio of leaf d. wt:leaf area), and trichome frequency (trichome number mm ) were markedly greater in leaves exposed to full solar radiation than in leaves acclimated to shade. The total thickness of sun leaves was 78% higher than that of shade leaves, mostly owing to a greater development of both palisade parenchyma and spongy mesophyll. The concentration, but not the composition, of leaf tissue phenylpropanoids varied significantly between sun and shade leaves, with a marked increase in flavonoid glycosides in sun leaves. Flavonoids occurred almost exclusively in the upper epidermal cells of shade leaves. By contrast, flavonoids largely accumulated in the upper and lower epidermis, as well as in the mesophyll tissue of leaves that were acclimated to full sunlight. Flavonoid glycosides were found exclusively in the secretory products of glandular trichomes of P. latifolia leaves exposed to high levels of light; luteolin 7-O- glucoside and quercetin 3-O-rutinoside were the major constituents. By contrast, verbascoside and an unidentified caffeic acid derivative constituted 72% of total phenylpropanoids secreted by glandular trichomes of shade leaves, whereas they were not detected in glandular trichomes of sun leaves. These findings suggest that the light-induced synthesis of flavonoids in glandular trichomes of P. latifolia probably occurs in situ and concomitantly inactivates other branch pathways of the general phenylpropanoid metabolism. This is the first report of the key role of glandular trichomes and of flavonoid glycosides in the integrated mechanisms of acclimation of P. latifolia to excess light.
实验在托斯卡纳沿海地区（北纬42°46′，东经10°53′）生长于茂密的海岸松（阴生植物）林下的狭叶海桐植株上进行，或在海滨沙丘（阳生植物）上进行。阴生和阳生环境下总的积分光子通量密度平均分别为1.67和61.4 μmol m⁻² d⁻¹。对叶片进行了形态结构分析、叶片组织和叶表面苯丙烷类化合物的定性和定量分析以及黄酮类化合物的组织化学定位。阳生叶面积达到阴生叶面积的57%，而暴露于全日照下的叶片的叶角（β）、硬叶指数（叶干重与叶面积之比）和毛状体频率（每毫米毛状体数量）明显高于适应阴生环境的叶片。阳生叶的总厚度比阴生叶高78%，这主要归因于栅栏薄壁组织和海绵叶肉的更大发育。阳生叶和阴生叶之间，叶片组织苯丙烷类化合物的浓度而非组成有显著差异，阳生叶中黄酮糖苷显著增加。黄酮类化合物几乎仅存在于阴生叶的上表皮细胞中。相比之下，黄酮类化合物大量积累在适应全日照的叶片的上表皮和下表皮以及叶肉组织中。黄酮糖苷仅在暴露于强光下的狭叶海桐叶片腺毛的分泌产物中发现；木犀草素7 - O - 葡萄糖苷和槲皮素3 - O - 芸香糖苷是主要成分。相比之下，毛蕊花糖苷和一种未鉴定的咖啡酸衍生物占阴生叶腺毛分泌的总苯丙烷类化合物的72%，而在阳生叶的腺毛中未检测到。这些发现表明，狭叶海桐腺毛中光诱导的黄酮类化合物合成可能在原位发生，并同时使一般苯丙烷类代谢的其他分支途径失活。这是关于腺毛和黄酮糖苷在狭叶海桐适应强光综合机制中的关键作用的首次报道。
