青藏高原东缘高寒草甸19种马先蒿属植物种皮纹饰特征及其生物学意义

Ornamentation characteristics of seed coats in nineteen plants of Pedicularis from alpine meadow in east Qinghai-Xizang plateau and its ecological significance

对分布于青藏高原东缘高寒草甸的19种常见的马先蒿属植物的种皮纹饰进行了扫描电镜观察研究,结果发现,该属植物种子表面纹饰有4种不同类型,即网纹型、膜质网纹、海绵质网纹和条纹型;膜质网纹可能是最进化的类型,海绵质网纹次之;网底为平滑的膜、膜下为精细网状,可能是网纹中较进化的类型,网底为精细网状结构的网纹次之,网底为密集不规则突起的网纹是网纹中的原始类型。条纹是原始特征,并向网纹演化;种皮纹饰具有一定的生物学意义,膜质的结构可能对种子有保温作用;另一方面海绵质网状结构及网纹中网底的精细网状结构可能还有利于种子在萌发时吸收水分。

The ornamentations of testa in nineteen plants of Pedicularis in the alpine meadows of east Qinghai--Xizang Plateau were studied by SEM. The results showed four types of testa ornamentations in the genus： reticulation, membraneous reticulation, spongy reticulation, and stria. Membranous reticulation ornamentation of testa is possibly the most evolutionary type in this genus and spongy reticulation takes second place. The type with subtle reticulation under a membrane ot bottom reticulation is more evolutionary among reuculation types. There may be evolvement in reticulation types from those with irregular tuber in the bottom reticulation to the ones with subtle reticulation in the bottom reticulation. Lengthways ridges of reticulation are universally extruded while widthways ridges of reticulation are located in the reticulation bottom of reticulation types. Whether there is evolution between reticulation and stria types is uncertain. The ornamentation of the testa is of some ecological significance. Seeds are probably protected by a membranous reticulation structure while spongy reticulation and subtle reticulation in the reticulation bottom may facilitate seeds imbibing water when germinating.