Higherplant which also known as vascular plant form a large group of plants that have xylem and phloem which make them able toconduct photosynthesis. They reproduce either by spores, cones, or flowers. In thishigher plants group they have three different type which is gymnosperms mainlythe conifers and cycads then angiosperms or also known as flowering plant andlastly the pteridophytes or fernssuch as clubmosses, and horsetails.
Firstly, gymnosperms isderived from two Greek words: gymnoswhich mean naked, and sperma, meaninga seed. This naked seed which not contained within an ovary or fruit allowedthem to be directly fertilized by pollination. It is develop on the surface of scales and leaves and then grow to formcone or stalk. It have four major phyla which is phylum Pinophyta (Conifers), Cycadophyta (Cycads), Gingkgophyta (Gingko), and Gnetophyta (Gnetophytes). Conifers, in the phylum Pinophyta, are the most numerous of the gymnospermsbecause they are woody and with vascular tissue. It also have cone bearingtrees and shrubs.
Conifers can be found mostly in the borealforests of the northern hemisphere. It is adapted to survive toface cold weather by having downward facing branches that allowed snowfall. It alsohave and specific biochemical properties that provide resistance to freezing. Conifers include pines, yews,redwoods, spruces, firs and cedars. As they are in gymnosperms, they did notproduce flower, but they have cones holding the seed. The female cones haveouter scale that carry ovules which after fertilization become seed. The pollenin male cones will moved by wind so called wind pollination. Even most of theconifers are monoecious it also have dioecious plant which mean they areseparated male and female plants.
For thecycads in phylum Cycadophyta they are gymnospermsbecause they have evergreen compoundleaves and dioecious where thefertilization take place after male conesproduce pollen that is carried by wind tofemale cones as they are separated plant. Typically they constitutes asingle, stout, cylindrical, woody trunk and a crown of large, hard and stiff, whichgrow directly from the trunk in a rosette formation. There are only threeextant families within the cycads today which is Cycadaceae, Stangeriaceaeand Zamiaceae. Next, Gingko is a genus of gymnosperm.They are closest relatives to the cycads but they have different characteristic.
Apart from having naked seed, they have nice small fan-shaped leaves and highertree which is up to 160 feet but slender in shape. They able to face wind andsnow. They are also resistant to disease and insect damage. The seed and leavesbeen used in medicine from the past till today in the entire world.
The gnetophyta are unique within thegymnosperms because they have vessel which mostlyfound in the angiosperms. The vessel is in the xylem which transport water. Thisphylum have three families. They are Ephedraceae,Gnetaceae, and Welwitschiaceae. Covering 70 species over three families,the gnetophyta are morphologically variable,including trees, shrubs, stumps, vines and creepers with leaf shapes rangingfrom opposite, to whorled, scale-like and straplike. The Ephedra found in southwestern North America as they been adapt byhaving tiny leaves.
They produce spores in cone-like structures which the malewill disperse their spore and female will receive the spores. Gnetum found on tropical and humidregion. As a member of gymnosperms they did not have flower and have a verystrong taproot system which allowed them to have height up to 50 feet. Endemic to the Namib Desert, Welwitschia were adapted to have long flatleaves which helps the plant to survive at higher temperature up to 65°C bykeeping the soil under the plant to stay cool and moist. The Namib Desert have averages fewer than 100 mm per year of rainbecause receives no rainfall during some years. They are around 80 percent of Angiospermswhich is the flowering plant out of all the living plant species in this earth.
As they are in higher plant group, angiosperms are vascular plants. They do havestems, roots, and leaves. The different of angiosperms and gymnosperms isangiosperms seed is in fruits meanwhile the flowers have male or femalereproductive organs. They need to undergo a pollination process beforethey can reproduce.
The male sex of Angiosperms called stamens. The pollengrain of the angiosperms is made at the anther which located at the end of the stamen.The pollen which develop from tissue contain many diploid microsporocyte thenundergoes meiosis to become microspores and then divides once by mitosis to beseparate will be taken to grow down to the stigma and style until reachthe micropyle of the ovule in the ovary. Or else known as pistil for thefemale part of the flower. Then the unique event happened in angiosperms iscalled double fertilization, where one sperms will unites with egg and formzygote and the other one will unites with polar nuclei to form endosperm. Afterthe unique fertilization a fruit and seed is develop.