<i>Subterraniphyllum thomasii</i>Elliott, Fossil Calcareous Alga the Evolutionary Link between Geniculate and Nongeniculate Coralline Algae: A Hypothesis

The Neogene sediments exposed in the Saurashtra region along the southwest coast India, consists of well preserved diversified coralline algae [1-5].The Subterraniphyllum thomasii Elliott, a fossil Calcareous alga has been reported from the Dwarka Formation (Lower to Middle Miocene) from Porbandar area, Saurashtara, Indian subcontinent. This is the first report of Subterraniphyllum thomasii Elliott from Lower-Middle Miocene sediments from the Indian subcontinent;however it has been documented earlier from Late Lutetian sediments of Kuchchh Basin, India. There is a controversy regarding the generic placement of the extinct species Subterraniphyllum thomasii Elliott as distinct genus of the geniculate coralline algae or not i.e. nongeniculate coralline algae [6,7]. However, the present specimens of Subterraniphyllum thomasii Elliott exhibit pinpointing features of both geniculate and nongeniculate coralline algae. Finally on the basis of our observations, we hypothesis that Subterraniphyllum thomasii Elliott may be transitional species and evolutionary link between geniculate and nongeniculate coralline algae.

美国岩榆愈伤组织的诱导及不定芽形成

以顶芽、嫩茎、叶片为外植体,对美国岩榆进行组织培养的初步研究。结果表明,用顶芽作外植体诱导愈伤组织的最佳培养基为MS+BA2.0mg·L-1+IBA2.0mg·L-1,诱导愈伤增殖的最佳培养基为MS+BA1.0mg·L-1+NAA1.0mg·L-1+IBA1.0mg·L-1;以幼叶为外植体产生愈伤的最佳培养基为MS+BA2.0mg·L-1+IBA2.0mg·L-1,诱导其愈伤增殖的最佳培养基为MS+BA1.0mg·L-1;用嫩茎段作外植体诱导愈伤组织的最佳培养基配比为MS+BA2.0mg·L-1+NAA0.5mg·L-1。诱导不定芽分化产生的外植体是嫩茎段,其最佳培养基组合为MS+BA1.0mg·L-1+NAA1.0mg·L-1+IBA1.0mg·L-1。

三种榆树幼苗对水分胁迫的生理响应

在人工模拟干旱的条件下,研究了自美国引种培育的岩榆、南方岩榆和国产白榆1 a生幼苗的叶片相对含水量(RWC)、电导率和叶绿素含量的变化情况,同时调查水分胁迫后期幼苗的存活率。结果表明:水分胁迫初期,3种榆树幼苗的叶片RWC、质膜透性、叶绿素a、叶绿素b及叶绿素总量均呈增加趋势;水分胁迫中期(第24天)白榆、南方岩榆的叶绿素总量呈现最大值,后开始缓慢下降,而岩榆仍继续上升至第30天后才开始下降,但各种幼苗叶片叶绿素a/b均增加。自然干旱初中期的RWC下降缓慢,后期失水迅速,白榆失水速率明显快于岩榆、南方岩榆。水分胁迫后期白榆叶片出现萎蔫,叶缘叶尖枯黄均早于南方岩榆、岩榆,萎蔫枯黄总数也最多,其次分别是南方岩榆、岩榆。因此,岩榆最耐干旱,南方岩榆次之,白榆较不耐旱。

美国岩榆育苗试验及苗期生长规律研究

在安徽滁州进行了美国岩榆引种育苗试验。结果表明：岩榆发芽率78%,1月中旬播种,32 d出苗,58 d时出齐。岩榆苗木前期生长均较慢,100 d时苗木平均高为16.5 cm,速生期始于7月份,且峰值出现在8月,到11月下旬生长逐渐停止。落叶时间较对照品种当地白榆迟7-14 d,且多数叶枯死后挂于枝头,经久不落。岩榆1 a生苗木平均高61.5 cm,最高达96 cm。