DIVISION GINKGOPHYTA

Western Mindanao State UniversityCollege of Science and Mathematics

Department of Biology and Natural ScienceBOTLEC-160

INTRODUCTION

• Phylum of seed plants represented by one living species, Ginkgo biloba. This species is restricted to China where it may be extinct in the wild. The group was well represented during the Mesozoic with worldwide distribution. Today, Ginkgo biloba is widely planted as an ornamental. It is especially useful as a street tree as it is tolerant of city polluted air.

CHARACTERISTICS

• Vegetative Characteristics: 

Deciduous trees bearing distinctive fan-shaped leaves. Branches with numerous spur shoots that bear the reproductive structures. Stems with extensive secondary growth producing considerable secondary xylem.

CHARACTERISTICS

• Reproductive Characteristics:

Dioecious trees. Megasporangiate trees bearing two ovules at the end of a stalk. Typically only one ovule develops into a mature seed. Integument includes three layers. The inner layer develops into the stoney seed coat. The outer two into a fleshy fruit-like tissue.

Because this tissue has a strong, unpleasant odor, "male" buds are typically grafted onto seedling roots to produce "male" trees for ornamental use. Microsporangiate ("male") trees bear catkin-like microsporangiate  strobili. These release pollen (microgametophytes) that are wind borne. Pollen produces a pollen tube that is haustorial and which delivers flagellated sperm to an egg in an archegonium of the female gametophyte.

GINKGOPHYTA: Ginkgo biloba

• Ginkgo biloba is the only living species in this group of seed-bearing plants, although the "ginkgophytes" are known in the fossil record dating back to the last period of the Paleozoic Era.

• The group reached its apparent height of diversity and distribution in the Mesozoic Era with fossils known virtually world-wide.

• The common name for this species is the "Ginkgo" or the "maidenhair tree". Although commonly planted and cultivated, Ginkgos are not native to Wise County. In fact, whether or not there are any remaining wild populations anywhere in the world, continues to be an unsettled question. It may be that the species owes its current existence to cultivation.

• Ginkgo biloba is a dioecious species, meaning that male and female reproductive structures are produced on separate trees. The fleshy seed coatings produced on female Ginkgos produce butyric acid. This compound is also produced by some anaerobic bacteria in animal digestive tracts and is responsible (in part) for the "distinctive" smell of vomit. For this reason, female Ginkgo trees are considered (by some) to be less desirable for cultivation than their male counterparts.

GINKGOPHYTA: Ginkgo biloba

• Ginkgophyta is a plant division of non-flowering trees originating over 250 million years ago, in which all plants except for one, Ginkgo biloba, have become extinct.

• Ginkgo bilobas are large, deciduous trees with unusual looking cones and distinctive leaves, they can live for up to a thousand years. A few hundred million years ago whole forests existed around the world filled with different species of Ginkgos, but now the one remaining species is native only to China.

GINKGOPHYTA: Ginkgo biloba

Gwapo si Gerick

GINKGOPHYTA: Ginkgo biloba Leaves

• Ginkgo leaves are bi-lobed, tough and more resistant to decay than other leaves. Some leaves are borne on long stems and turn yellow, die back in winter, then reappear in spring, while others are on shorter stems that may survive the winter.

GINKGOPHYTA: Ginkgo biloba STEM

• The bark of Ginkgos is fissured and the trunks may reach to 4m in diameter.

• The vascular system of Ginkgos, and also conifers, are different to that of flowering plants. While flowering plants have a series of tube-like cells to conduct water, Ginkgos have connecting cells with tiny perforations, these are valves that close when water is in short supply so that turgidity is preserved.

GINKGOPHYTA: Ginkgo biloba

REPRODUCTION & SURVIVAL

• Ginkgos are dioecious. The male cones grow from the shoot tip in clusters and release pollen. The female ovules (cones) appear in twos on the end of a stalk and do not look much like the cones of conifers. Each ovule has a drop of fluid, the pollination drop, that traps pollen to enable fertilisation.

Ginkgo biloba w/ male cone

Cone on female Ginkgo Ovules

GINKGOPHYTA: Ginkgo biloba

REPRODUCTION & SURVIVAL

• Ginkgo sperm cells are motile, swimming to the ovule using thousands of hairs. This is something that occurs in cycads too (see previous blog) and in ferns, but not conifers or flowering plants, so is  a throwback to a more primitive form of reproduction. Once fertilized the ovule grows into something resembling a fruit containing the seed.

Cone on female Ginkgo Ovules

GINKGOPHYTA: Ginkgo biloba

REPRODUCTION & SURVIVAL

• Ginkgo seedling

Ginkgo seeds contain two cotyledons (seed leaves), but these never expand or emerge, instead they remain embedded in the seed providing nutrition for the seedling. The first leaves to appear above ground are true leaves with the distinctive Ginkgo shape, this is called hypogeal germination.

Cone on female Ginkgo Ovules

GINKGOPHYTA: Ginkgo biloba

REPRODUCTION & SURVIVAL

• Ginkgos have a few clever ways of surviving and reproducing:

• Like cycads, Ginkgos have been known to change sex, so that the male trees start producing ‘fruits’ and seeds. This is an effective way of propagating when there are no females around.

Cone on female Ginkgo Ovules

GINKGOPHYTA: Ginkgo biloba

REPRODUCTION & SURVIVAL

• Ginkgos have a tendency to put out suckers from the ground that point upwards, but older trees sometimes also have odd downward growths, called Chichi, hanging from a single branch like stalactites. When these growths hit the ground they can start growing new roots and eventually form into a new tree, this is seems to be a form of reproduction for when the main tree is coming to the end of its life.

• If Ginkgos are hacked right back to the bare trunk they can regrow, either growing from the damaged stem or by putting out new shoots from the ground.

• Ginkgos are also very resistant to pests, diseases, fires and pollution.

Ovules

GINKGOPHYTA: Ginkgo biloba

• Ginkgo biloba contains Flavonoids and Terpenoids which are naturally occurring chemical groups found in plants.

• Flavonoids

• Use for the plant: pigmentation, assisting in nitrogen fixation and cellular function

• Use for humans: thought to have anti-allergic, anti-inflammatory, anti-microbial, anti-cancer and anti-diarrheal properties although this is not fully proved.

• Terpenoids

• Use for the plant: provide pigmentation and smell. They are thought to act as a deterrent to herbivorous insects and an attractant to insects that may eat herbivorous insects. They also are found in flowering plants and are used to attract pollinators. They may have antioxidant benefits for plants.

• Use for humans: they have been used in traditional medicines for many years, although their effectiveness is not proved, they may have antibacterial properties and they may also have antioxidant benefits.

Ovules

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