Affinities of Ginkgo | Class Ginkgopsida | Gymnosperms | Botany

In this article we will discuss about the affinities of ginkgo which belong to the family of class ginkgopsida.

A. Relation to Ferns:

The similarities between Ginkgo and ferns are:

i. The leaves of Ginkgo shows striking simi­larity with Adiantum (maiden hair fern) in form, shape and venation and hence the name maiden hair tree for Ginkgo tree.

ii. The sperms are motile and multiciliated.

B. Relation to Pteridosperms:

Ginkgo resembles the pteridosperms in having the following characteristics:

i. The leaf of Ginkgo may be linked to the wedge-shaped pinnule of pteridosperm.

ii. There is accumulation of abundant reserve food material and lignification in the integu­ment prior to fertilisation.

iii. The collar in the ovule of Ginkgo may be linked to the cupule of pteridosperm ovule.

C. Relation to Cycadales:

Ginkgo resembles the Cycadales in having the following characteristics:

i. The stem anatomy shows a broad cortex, large pith and numerous mucilage ducts. Mucilage ducts are also present in leaves, petioles, sporangia, embryos or even in roots.

ii. Both the cotyledonary leaves and foliage leaves bear mesarch xylem.

iii. The presence of nucellar beak with a distinct pollen chamber.

iv. The micro- and megasporophylls are of foliar nature.

v. The sperms are large and motile with spiral band bearing numerous cilia.

vi. The presence of extensive free-nuclear divi­sions in the early stage of embryogeny.

vii. The embryo with two cotyledons.

D. Relation to Cordiatales:

The similarities between Ginkgo and Cordaitales are:

i. The presence of double leaf trace.

ii. The presence of motile sperms.

iii. The presence of endospermic beak in the mature ovules.

E. Relation to Coniferales:

The resemblance between Ginkgo and Coniferales are:

i. The plants are tall trees showing excurrent branching.

ii. The branches are dimorphic bearing two types of shoots — long shoots and dwarf shoots.

iii. The presence of pycnoxylic wood.

iv. The mature wood shows pitting and Bars of Sanio.

v. The leaves are with sunken stomata.

vi. The two lateral ears in the pollen exine of Ginkgo may be linked to the wings of Pinus pollen.