Clarkson D T, Robards A W, Stephens J E, Stark M
Division of Plant Sciences, University of Bristol, Long Ashton Research Station, Bristol BS18 9AF.Department of Biology. University of York, York YO1 5DD, U.K.
Plant Cell Environ. 1987 Jan;10(1):83-93. doi: 10.1111/j.1365-3040.1987.tb02083.x.
The development of suberin lamellae in the hypodermis of Zea mays cv. LG 11 was observed by electron microscopy and the presence of suberin inferred from autoliuorescence and by Sudan black B staining in nodal (adventitious) and primary (seminal) root axes. Suberin lamellae were evident at a distance of 30-50 mm from the tip of roots growing at 20°C and became more prominent with distance from the tip. Both oxygen deficiency and growth at 13°C produced shorter roots in which the hypodermis was suberized closer to the root tip. There were no suberin lamellae in epidermal cells or cortical collenchyma adjacent to the hypodermis. Plasmodesmata were not occluded by the suberin lamellae: there were twice as many of them in the inner tangential hypodermal wall (1,14 μn ) as in the junction between the epidermis and hypodermis (0.54 μm ). Water uptake by seminal axes (measured by micropotometry) was greater at distances more than 100 mm from the root lip than in the apical zone where the hypodermis was unsuberized. In the more mature zones of roots grown at 13°C rates of water uptake were greater than in roots grown at 20°C even though hypodermal suberization was more marked. Sleeves of epidermal/hypodermal cells (plus some accessory collenchyma) were isolated from the basal 60 mm of nodal axes by enzymatic digestion (drisclase). The roots were either kept totally immersed in culture solution or had the basal 50 mm exposed to moist air above the solution surface. In both treatments the permeabilities to tritiated water and Rb were low (circa 10 mms ) in sleeves isolated from the extreme base. In roots grown totally immersed, however, the permeability of sleeves increased 10 to 50-fold over a distance of 40 mm. In roots exposed to moist air the permeability remained at a low level until the point where the root entered the culture solution and then increased rapidly (> 50-fold in a distance of 8 mm). Growth of roots in oxygen depleted (5% O ) solutions promoted the development of extensive cortical aerenchymas. These developments were not associated with any reduction in permeability of sleeves isolated from the basal 40 mm of the axis. It was concluded that the presence of suberin lamellae in hypodermal walls does not necessarily indicate low permeability of cells or tissues to water or solutes. The properties of the walls (lamellae?) can be greatly changed by exposure to moist air, perhaps due to increased oxygen availability.
通过电子显微镜观察了玉米品种LG 11下胚轴中栓质化薄片的发育情况，并通过自发荧光以及在节（不定）根和初生根轴中用苏丹黑B染色推断栓质的存在。在20°C下生长的根，距根尖30 - 50毫米处栓质化薄片明显可见，并随着距根尖距离的增加而更加显著。缺氧和在13°C下生长都会使根变短，其中下胚轴在更靠近根尖处就发生了栓质化。与下胚轴相邻的表皮细胞或皮层厚角组织中没有栓质化薄片。胞间连丝未被栓质化薄片阻塞：在内切向的下胚轴细胞壁（1.14μm）中的数量是表皮与下胚轴交界处（0.54μm）的两倍。初生根轴（通过微量测压法测量）在距根冠超过100毫米处的水分吸收比下胚轴未栓质化的根尖区域更大。在13°C下生长的根的更成熟区域，即使下胚轴栓质化更明显，水分吸收速率也比在20°C下生长的根更高。通过酶解（drisclase）从节根轴基部60毫米处分离出表皮/下胚轴细胞套（加上一些附属厚角组织）。根要么完全浸没在培养液中，要么基部50毫米暴露在溶液表面上方的潮湿空气中。在这两种处理中，从最基部分离出的细胞套对氚化水和铷的渗透性都很低（约10毫米/秒）。然而，在完全浸没生长的根中，细胞套的渗透性在40毫米的距离内增加了10到50倍。在暴露于潮湿空气中的根中，渗透性一直保持在低水平，直到根进入培养液的位置，然后迅速增加（在8毫米的距离内增加超过50倍）。在缺氧（5% O₂）溶液中生长的根促进了广泛的皮层通气组织的发育。这些发育与从轴基部40毫米处分离出的细胞套的渗透性没有任何降低相关。得出的结论是，下胚轴细胞壁中栓质化薄片的存在并不一定表明细胞或组织对水或溶质的渗透性低。细胞壁（薄片？）的特性可能会因暴露于潮湿空气中而发生很大变化，这可能是由于氧气供应增加所致。
