Angiosperms are a large group of seed producing flowering plants characterized by the enclosure of the seeds within the female reproductive organ of the flower known as carpel. Typical examples include grasses, herbs, shrubs and most of the trees.
Angiosperms constitute the largest and probably the most diverse group within the plant kingdom having approximately 300,000 species worldwide. They also represent about 80 percent of all the green plants present on earth.
Gymnosperms are a group of plants in which are characterized by being flowerless. The literal meaning of the word ‘gymnosperm’ is ‘naked seeded’. These plants produce cones and seeds instead of flowers. Contrastingly to angiosperms, the seeds of gymnosperms are not enclosed in an ovary or carpel.
Gymnosperms have about 1000 living species distributed in various regions of the world. Typical examples of gymnosperms include conifers, gingko, and cycads. Out of these, conifers constitute the most abundant extant group of gymnosperms embedding a great variety of the group.
As angiosperms and gymnosperms compose the two major families of most of the plants present, it is important to look at the key differences between the two types. Although both are seed producing pants, they are quite different from each other. Consequently, let us take a look at them one by one.
In the early classifications by plant scientists, all the seed-producing plants were placed in a single group. However, with the advent of knowledge and research, it became evident that the two types cannot take a single hold in the plant kingdom.
Fossil evidence from recent research is pointing towards the fact that many seed plants were present before any evolutionary advancements took place such as the origin of seeds, cones, vascular cambium, vessels and secondary growth. Therefore, some scientist think that it is not appropriate to keep both in the same division, while there are many others having the opposite views.
Despite the differences, the commonly accepted divisions of the gymnosperms are:
It is believed that angiosperms or flowering plants have been emerged or evolved relatively recently as compared to the gymnosperms. The only earliest fossils of these plants which are clearly recognizable are pollen grains in rocks.
The very first angiosperms are assumed to be probably small trees or shrubs and hold evolutionary transformation from a gymnosperm via a complex series of events. The most obvious among these events could be the conversion of the sporophylls of gymnosperms into primitive stamens and carpels which we see in today’s flowering plants.
In contrast to the many divisions of the gymnosperms, angiosperms have only a single division known as Magnoliophyta / Anthophyta.
The leaves of angiosperms have a flattened structure mostly. Furthermore, the veins of the leaves of dicots form an interconnecting meshwork while those of the monocots are parallel and do not interconnect with each other.
Quite contrastingly, the leaves of gymnosperms are mostly scaly or needle like in appearance.
Sieve Cells v/s Sieve Tube Elements
Sieve cells are a type of cells in plants which perform the function of the conduction of food from the parts of the plants which carry out photosynthesis to rest of the plant.
They are the only cells which carry out the function of food transport in gymnosperms and are present as individual cells.
Whereas, in angiosperms, a sieve tube is present in which the individual compartments of the cells (the cells) are connected with each other through small pores thus forming a complete channel. Moreover, the sieve tube elements or channels are often surrounded by supportive cells called companion cells.
The structure of gymnosperm wood is homogenous and simple. The only conducting elements in them are tracheids (except for a few species). Tracheids belong to a type of water conducting cells present in the xylem tissue of plants and have no perforations in the cell wall.
In many species, the wood of gymnosperms is distinguished by the presence of heartwood or sapwood. While sapwood is characterized by an active conducting channel of water, heartwood is inactive and thus does not perform any function of water conduction.
Moreover, the wood of gymnosperms is often interspersed with medullary rays at regular distances. Since they are oriented horizontally, they typically perform the function of horizontal conduction of the solutes.
The structure of the wood of angiosperms is inhomogeneous and more varied than that of gymnosperms. Typically, there are two types of arrangement of vessels in them. In one type, the wood contains scattered pores while in the other it has ring shaped pores.
The angiosperm, like the gymnosperms, contains medullary rays except that they are larger in size. Another difference is that the rays of angiosperms do not contain tracheids as frequently as they are observed in the gymnosperms. Also, there is a variety of rays in angiosperms in that both single- and multi- layers are present in different species.
Perennial v/s Annual
Since the basic form of gymnosperm plants is woody, they are mostly perennials in nature. A perennial plant is the one which lives for many years and last for period longer than one or two years. On the other hand, since angiosperms are flowering plants they are mostly annual or biennial plants, meaning that they complete their life cycle annually or every two years, respectively.
Gymnosperms and angiosperms also differ in their reproduction cycles and systems. The key differences are as follows:
- The angiosperms contain female gametophyte in an ovule which is enclosed in a specialized structure of the flower called ovary. Contrastingly, the female gametophyte in gymnosperms is present openly within the bracts of the cones and are not enclosed in the ovules or ovaries.
- The life cycle of angiosperm reproduction is characterized by double fertilization, which is completely absent in gymnosperms.
- The male and female gametophytes are part of a single structure i.e., flower in angiosperms; whereas these are present on separate cones in the case of gymnosperms.
- Wind is an important factor for the pollination in case of gymnosperms as the male and female cones are located on separate plants. Contrarily, since both the female and male reproductive parts are present within a single flower in most of the angiosperms, thus they do not need wind for their dispersal and hence pollination.
The flowering plants hold considerable economic significance not only for humans but also for herbivores. Most importantly, they are the prime source of food for everyone. The edible examples include fruits, vegetables, grains, oils, nuts and sugars.
Apart from the food industry, they are also important sources for a number of other needs such as ornamentals, medicines, dyes, fibers and fuels.
Similar to angiosperms, gymnosperms are also economically important except that their products differ from that of the angiosperms. Typical examples include the use of gymnosperms for the production of paper, lumber and resin.
Some of the gymnosperms also serve as food sources. For example, Burrawang nut is a major source of starch for a part of Australian inhabitants. Similarly, Ginkgo serves as a common ingredient of many of the chines dishes.