Instant Notes: Plant Biology

in the British hartstongue and the tropical birdsnest fern (both Asplenium) and some tropical climbing ferns have branched leave ...

containing a cyanobacterium that fixes nitrogen (Topic M2) and roots trailing into the water from the nodes. Megasporangia and m ...

found in shady situations under dense tree canopy or in rocky crevices. In the tropics, many ferns are epiphytic and they can be ...

Section Q – Spore-bearing vascular plants Q4 Evolution of the seed The seed habit derives from a heterosporouscondition similar ...

There are some intermediate stages represented among early fossil seed plants. The megagametophyte is reduced in size and retain ...

Section R – Seed plants R1 Early seed plants Pteridosperms Thepteridosperms, or ‘seed ferns’, were the earliest seed plants (Top ...

by bracts making the whole structure look remarkably like a flower (Fig. 1). It is likely that some, at least, were insect-polli ...

with sporangia at their tips (Fig. 3). Their relationships are obscure, perhaps with the pteridosperms, but their leaves resembl ...

Section R – Seed plants R2 Conifers Conifers, the Pinopsida, are the largest and most important seed plant class except for the ...

and east Asia. They also cover extensive areas in temperate parts of the southern hemisphere. They are much less common in the t ...

Leaves The leaves of living conifers are all simple and most are shaped like needles, sometimes long, or scales, semicircular or ...

conifers but in some there are more. The cones themselves are produced in the axils of scale-leaves in pines, or at the tips of ...

When the ovule is receptive, the cone scales open apart slightly and a drop of sticky liquid is exuded from the micropyle. Polle ...

Section R – Seed plants R3 CYCADS, GINKGO AND GNETALES Cycads The cycads, Cycadales, are a group of palm-like plants that are th ...

places. The trunks are thick, normally unbranched, and typically to about 2 m tall, though a few grow to 15 m and a few have bra ...

micropyle containing sugars and amino acids, and the pollen is trapped in this. Some cycads are pollinated by insects, mainly we ...

female gametophyte. Two archegonia are formed, each with a neck of four cells, a canal cell and an egg. By the time the pollinat ...

Male and female organs are borne in separate cone-like structures (Fig. 3), usually on separate plants, although a few species a ...

Section R – Seed plants R4 Evolution of flowering plants Key Notes The fertile parts of a flower are a further reduction from th ...

The flower of an angiosperm (Topic D1) represents a further reduction and specialization of the heterosporous form discussed in ...