What is the structure of conifers?

What is the structure of conifers?

Conifers comprise a monophyletic group of highly branched trees or shrubs with simple leaves, the latter a possible apomorphy shared with the ginkgophytes (Figure 5.1). Leaves of conifers are often linear, acicular (needle-like), or subulate (awl-shaped; see Chapter 9), although they are sometimes broad and large.

Where are Microsporangia on a pine tree?

gymnosperms. Microsporangia, or pollen sacs, are borne on the lower surfaces of the microsporophylls. The number of microsporangia may vary from two in many conifers to hundreds in some cycads. Within the microsporangia are cells which undergo meiotic division to produce haploid microspores.

What is the microgametophyte of a pine tree?

F Detail of the male sporangium (male carrier of spores) of pine. The sporangium contains sporogenic tissue (microsporocytes). Each microsporocyte forms four microspores through a meiotic division. Subsequently, each microspore forms a pollen grain (the microgametophyte) through mitosis.

What type of tree is conifer?

Conifers are typically (but not always) evergreen trees with needle-like foliage. Conifers are a type of gymnosperm plant and are among the oldest living plants. Pine trees, redwoods, ginkgo trees, and douglas fir are all types of conifer trees.

What is special about coniferous trees?

Many coniferous trees have the ability to patch themselves up. If attacked by a burrowing insect the tree can secrete a scented, gummy resin that fills over the hole and hardens, protecting the tree from further damage. The scent can also deter insects from coming too close.

What are the microsporangia on a pine tree?

Microsporangia are organs that contain microsporocytes, immature pollen grains. The microsporocytes develop into pollen grains with four cells each. The four cells of the pollen grain are haploid, in that each contains one set of chromosomes.

Do conifers have male and female cones?

All conifers produce male and female cones. Sometimes on the same tree, sometimes not. The pinecones we see are only the female cones. The male cones are much smaller and not showy.

Why are trees called conifers?

They are called conifers because they are conical in shape.

Where are the Megagametophyte located?

The Megagametophyte and the Central Cell The megagametophyte, or embryo sac, is situated within the body of nucellus parenchyma cells, which are covered by the integuments (Figure 1A).

What is microsporangia and megasporangia?

Megasporangia are larger whitish or yellowish often lobed with 1-4 haploid megaspores. Microsporangia are smaller; yellowish-reddish globular reniform structures which produce a large number of haploid microspores.

What shape are coniferous trees?

What is a coniferous tree. Evergreen cone-shaped trees, growing needle- or scale-like leaves are called conifers. Most trees growing in these forest regions are cone-bearing gymnosperms, meaning their seeds are bore exposed, without any outer enclosure, in the form of cones.

How many nuclei are in a megagametophyte?

In angiosperms, the megagametophyte is reduced to only a few nuclei and cells, and is sometimes called the embryo sac. A typical embryo sac contains seven cells and eight nuclei, one of which is the egg cell.

What are microgametophytes in seed plants?

Seed plant microgametophytes consists of several (typically two to five) cells when the pollen grains exit the sporangium. The megagametophyte develops within the megaspore of extant seedless vascular plants and within the megasporangium in a cone or flower in seed plants.

What is the process of embryogenesis in conifers?

Embryogenesis in conifers starts with a single fertilization event in which the larger male gamete fuses with the egg cell. The zygote, which develops within the haploid megagametophyte, undergoes initially several rounds of duplication before cellularization.