Anomalous Secondary Thickening in Dracaena
Anomalous Secondary Thickening in Monocots
Before going to the secondary thickening in Dracaena, first see what anomalous secondary thickening is and how the process of anomalous secondary thickening happens in plants.
What is Anomalous Secondary Thickening?
Ø In many plants, the pattern of the secondary thickening shows deviation from the normal type.
Ø The term “Anomalous Secondary Growth” is given for this deviation or variation.
Ø The anomalous secondary growth is more common in tropical plants.
Ø Anomalous secondary thickening is NOT an anomaly or disease in plants; rather it is an adaptation to suit the habit and habitat of the plant.
(General Characteristics of Caytoniales)
What are Caytoniales?
Ø Caytoniales were a small group of extinct Gymnospermic plants.
Ø First described by Hamshaw Thomas in 1925 from the late Triassic period.
Ø Caytonia is a berry-like cupules with numerous small seeds.
Examples of Caytoniales
Ø Leaves: Sagenopteris
Ø Microsporophylls: Caytonanthus
Ø Megasporophylls: Caytonia and Gristhorpia
Glossopteridales General Characteristics
Characteristics of Glossopteridales: Fossil Gymnosperm
Ø Glossopteridales included an extinct group of seed plants (Gymnosperms).
Ø They were originated during the Permian period on the Gondwana Continent.
Ø They became the dominant vegetation in the Permian period.
Ø They extinct completely by the end of the Triassic period.
Ø The order name derived from the genus Glossopteris
Ø Glossopteris is the best-known member of Glossopteridales