Graham Centre for Agricultural Innovation (NSW Department of Primary Industries and Charles Sturt University), School of Agricultural & Wine Sciences, Locked Bag 588, Charles Sturt University, Wagga Wagga NSW 2678, Australia.
Am J Bot. 2013 Dec;100(12):2307-17. doi: 10.3732/ajb.1300034. Epub 2013 Dec 9.
Solanum elaeagnifolium (silverleaf nightshade), having originated in the Americas, is now a serious summer-growing, perennial weed in many countries, including Australia. Most surfaces of the plants have a dense covering of trichomes, giving them a silvery-white appearance, hence the common name. We aimed to identify structural and functional properties of its leaves, especially the trichomes, that may affect the uptake of foliar-applied tracer dyes.
The structure of leaves of Solanum elaeagnifolium was examined by light and scanning electron microscopy. The potential for transport of materials between trichomes and veins was studied with symplastic (carboxyfluorescein diacetate) and apoplastic (lucifer yellow) tracer dyes.
Mature leaves had a dense covering of complex, stellate trichomes on both surfaces, particularly the abaxial. The basal cells of Solanum elaeagnifolium trichomes penetrated into the underlying palisade mesophyll layers. The innermost lobes of these basal cells sometimes contacted the bundle sheath of the veins, but were not observed to directly contact the xylem or phloem. We found that neither symplastic nor apoplastic dyes were transferred between the basal cells of the trichomes and the vascular tissues. The trichome layer repelled water-based tracer dyes, while one of four adjuvants tested facilitated entry of both symplastic and apoplastic dyes.
Our results did not support a transport function for the trichomes. The trichomes may protect the mesophytic leaves from invertebrate herbivory, while also probably decreasing radiation absorbed resulting in cooler leaves in this summer-growing species.
茄属植物银叶茄（silverleaf nightshade）起源于美洲，现已成为包括澳大利亚在内的许多国家夏季生长的多年生杂草。植物的大部分表面都有密集的毛状体覆盖，使它们呈现出银白色的外观，因此有了这个常见的名称。我们旨在确定其叶片的结构和功能特性，特别是毛状体，这些特性可能会影响叶面应用示踪染料的吸收。
通过光镜和扫描电子显微镜观察银叶茄叶片的结构。通过使用质体（羧基荧光素二乙酸酯）和质外体（荧光素黄）示踪染料研究物质在毛状体和叶脉之间的运输潜力。
成熟叶片的两面，特别是背面，都有密集的复杂星状毛状体覆盖。银叶茄毛状体的基细胞穿透到下面的栅栏状叶肉层中。这些基细胞的最内层裂片有时与叶脉的鞘接触，但没有观察到它们与木质部或韧皮部直接接触。我们发现，无论是质体染料还是质外体染料都没有在毛状体的基细胞和维管束组织之间传递。毛状体层排斥水基示踪染料，而我们测试的四种助剂中的一种促进了质体和质外体染料的进入。
我们的结果不支持毛状体的运输功能。毛状体可能保护中生叶免受无脊椎动物的侵害，同时也可能减少吸收的辐射，使这种夏季生长的物种的叶片更凉爽。
