Grade 11 Botany Note
The term algae has been derived from the latin word alga means seaweed. The study of algae is called phycology or algology. They all are multicellular except some unicellular forms; chlamydomonas. Algae mostly aquatic and main form green producer of fresh and marine water. Some occurs in moist soil. The unicellular microscopic form of chlamydomonas is the most primitive one. Colonial form isvolvox .Filamentous forms unbrached spirogyra and branched cladophora. The siphonales branched profusely and are coenocytic: vaucheria, charales.
Algae generally reproduce both by the sexual and asexual reproduction.
Based on the presence of the pigments the alga is classified into 11;
This is green algae; it is largest class of algae, which includes about 425 genera and 7000 species. The chief pigment is chlophyll-a and b and small amount of carotenoids.
They are mostly fresh water, through terrestrial and marine forms are also found.They are cosmopolitan in nature. Some grow in the peculiar habit, while other cannot survive. The algae; chlamydomonas yellowstonensis, and haematococcus nivalis occurered in the snow covered mountain tops.
Range of thallus structure:
Parenchymatous forms:Ulva, non-motile colonial form:Hydrodictyton, colonial motile form;Eudorina. The cell is eukaryotic type. The inner layer of cell wall is made of cellulose and the outer layer is made of pectose. The chloroplast shows the various sizes. Cup shaped in chlaydomonas , spirally coiled in spirogyra.
The store food material is starch. The reproduce by vegetative, asexual, sexual methods. Sexual reproduction is isogamous (chlamydomonas braunii) and oogamous in oedogonium.
Asexual reproduction takes place by aplanospore formation.
Phaeophyceae (brown algae): it possess of brown color pigment such as carotenoid, fucoxanthin in large pigment such as carotenoid, fucoxanthinin large amount chlorophyll-a and c also present. The brown algae are mostly marine, however a few are fresh water form like pleurocladia,Bodanella. They are attaching the substratum by aholdfast.
1. They are multicellular, no unicellular. The gaint kelps are grow to 30 m in height.
2. Theypossess chlorophyll-a and c, carotenoids and fucoxanthin.
3. The outer mucilaginous layer has alginic, fucinic acid. The inner layer is cellulosic.
4. laminarian starch and mannitol is the reserve food.
5. Air bladder helps in floating.
6. They reproduce vegetative, asexul and sexual.
The member of this class includes red algae. They are present in fresh water, as well as marine water.
Some red algae grow as epiphytes e.g. Polysiphonia violacea is epiphytic on Fucus vesiculosus. Parasitic forms have also been reported from red algae eg, Harvevella pachyderma, Polysiphonia fastigiata.
1. It is unicellular forms eg Porphyridium and Chroothece.
2. heterotrichous filament eg Goniotrichium and Asterocystis.
3. True parenchymatous form:Porphyra, Ulva, Bangia.
4. The outer pectic the inner layer is cellulosic.
5. Typical eukaryotic structure present in cell.
6. The pigment is chlorophyll-a ,bβ-carotene,xanthophyll and r-phycocyanin, r- phycoerythrin.
7. The reserve food is Floridian starch.
8. Reproduction takes place by vegetative, aseual and sexual.
9. Some species shows the alternation of generation.
Occurrence: the genus comprises more than 400 species. Spirogyra is common fresh water, free floating green algae. Few species of spirogyra remain attached to the substratum.
They are multicellular thread and unbranched. The cell consists of cell wail and protoplast. The cell wall is made up externally pectin and inner cellulosic. Due to presence of, mucilage they are slippery. Hence spirogyra often called scum or water silk. Spirally coiled ribbon shaped chloroplast. A single large nucleus is present in the centre of cell. The nucleus hangs in the central vacuole. It is heldin the position by delicating,radiating cytoplasmic strands.
Vegetative reproduction; fragmentation, is caused is the death of some intercalary cell, or by the injury. Filaments break into two or several small pieces. Each fragment consists of one or few living cell.
Asexual reproduction: it takes place by following methods:
1. Akinetes : In s. farlowii akinetes formation occurs during the unfavourable conditions. It is thick walled resting spores. On return of favourable conditions akinetes germinate to produce a new filament.
2. Aplnospore: Aplanospore is thin walled non motile spores. They arise singly inside the cells. The protoplast of cells loses the water and contracts. It rounds off and secrete the thin wall around it form aplanospore. The parent cell when rupture it released down.
Sexual reproduction: it is takes place by conjugation. The donor cell is designed asmale gamete while the recipient cell is designated as female gametes. In spirogyra any vegetative cell produces the gamete and there are no morphological differences between male and female gametes. Thus morphologically thegametes are isogamous and physiologically anisogamy. Conjugation takes place by two methods:
1. Scalariform conjugation: It occurs between the two filaments of cell. At the time of conjugation two filaments come in contact and lie parallel to each other. The filaments form tubular outgrowth or papillae from their opposite cells. The end walls of papillae are dissolved by the enzyme action to form a conjugation tube between the two cells. Due to the formation of several conjugation tubes the two filaments give a ladder like appearance hancre it is called scalariform conjugation. The protoplast of cell function as gametes. The protoplast of one cell squeezes its way through the conjugation tube and passes into the cell of the filament, to form zygospore.
2. Lateral conjugation:
Occur in between the cell of same filament. It takes place in two ways:
a) Indirect lateral conjugation: in this method the two adjacent cells develop papillae on the lateral sides of septum. The common wall is ruptured by the action of enzyme. Both gametes fuse to form zygospore.
b) Direct lateral conjugation:
It is a primitive type of conjugation. The lower surface behave as female and upper surface behaves as male in the same filament the male gametes produced boring organ , this conical process produced the pore in the middle of septum. This two gametes fuse to form the zygospore.
The zygospore is made up of three layers wall around themselvesand represent the diploid phase, by the decay of this layer of the female gametes and sink to the bottom of water. During the germination the zygospore divides mitotically, four haploid nuclei. Three of these haploid nuclei degenerate.
The zygospore to form single filament. On return of favorable condition the zygospore absorb water and swells up. The outer two layer burst and inner layer to form the germ tube, it divides transversily to form two celled structure. The lower cell is colorless and functions as rhizoid. The upper green cell divide repeatedly to form a new filament.
1. This the amphibian plants.
2. Small terrestial plant live in the moist and damp place, require more water for reproduction.
3. 25000, species of plants may be thalloid as in the Hapatiacea or leaf as in moss.
3. Rootis not well developed, rhizoids unicellular or multicellular.
4. Cuticle is absent andpart of plant absorbs the water and mineral.
5. Plant body is gametophytic, reproduce sexually by formation of gametes. Plant body or vegetative cell consists of haploid no. of chromosomes.
6. Gametes are produce in the reproductive structure; antheridium and archegonium.
7. As a result of sexual reproduction to form a zygote, which is diploid embryo inside the plant (in site) sporophytic.
8. Diploid in nature reproduce asexually by the formation of spore, as result of meiosis, haploid spore may be homosporous or heterosporous.
9. Alternation of generation is distinct but gametophytic generation is dominated over the sporophytic generation.
10. They are non-vascular plants or conducting tissues are absent.
1. They are found in the damp and moist places.
2. Plant body is dorsoventrally flattened, dichotomously branched, may formed rosette like structure.
3. Dark green in color dorsally and ventral surface is pale green.
4. Ventral surface produced the rhizoids; unicellular, smooth walled tuberculated.
5. Absence of columella.
M. himalayansis these two spp. are commonly found in Nepal.
Distribution: Foot hills and the upper hills, cold countries, terai, moist, near the tap etc., appear during the rainy season, winter season.
1. Vegetative reproduction:
a) By the death and decay of older part of the thallus.
b) By the production of adventitious buds
c) By the formation of Gammae.
2. Sexual reproduction:
a) Plant body is gametophytic usually reproduce sexually to produce the gametes having haploid no. chromosome.
b) Plant body is diocieous. Male thalli usually produce antheridiospore and female thalli produce the archegoniospore.
The plant body of marchantia is of gametophyte which is called a thallus. The mature thallus may attain the length of 1-10cm. it is a dark green in color and possess the prominent midrib. The midrib is marked by the shallow groove in the dorsal surface and shows the rosette type. Along the midrib, special cup like structures called gemma cups is present.
The ventral surface of the thallus bears two or more rows of violet, multicellular plate likes scales on the either side of the midrib. Scales are of two types: Ligulate and appendiculate.
The ligulate scales are small and have no appendages. Scales gives the protection to the growing point.
The ventral surface of the thallus also bears numerous rhizoids. They are pale brown, unicellular and branched. The rhizoid are of two types; smooth walled and tuberculated walled rhizoid. In the smooth walled rhizoid contain the smooth wall in the inner wall and in tuberculated rhizoids the inner wall possesses the peg like structure. They help in plant fixation and absorption of water and minerals.
In the reproductive stages thalli bears small upright, stalked structure called antheridiophores and archegoniophores. This bears male sex organ and female sex organ respectively.
Internal structure of the thallus:
A v.s. of the thallus shows the two distinct regions, the upper photosynthetic and storage region. The upper epidermis is single layered of thin walled cells. It is interrupted by several air pores. Air pores are barrel shaped consisting of 4-5 superimposed cells having both an upper and lower opening. The air pores are helps to exchange the gaseous during the respiration and photosynthesis the photosynthesis region consist of large no. of air chambers surrounded by the single celled thick 4-8 cells high septa.
The storage region consists of compactly arranged thin walled parenchymatous cells. Some cells may have single oil body or filled by the mucilage.
The lowermost layer of the storage region is lower epidermis. Rhizoids and scales are borne form certain cells of lower epidermis.
The sexual reproduction of the marchantia is oogamous type. Marchantia plants are dioecious , i.e. male and female sex organ develop in separate thalli. The male sex organ is the antheridia and female sex organ are called archegonia. The sex organ of marchatia is borne on special erect and stalked branches called the gametophores.
The gametophore bearing the antheridia is called antheriaophore or stalk of Male receptacle whereas the gametophore bearing archegonia is called archegoniophore or stalk of female receptacle.
Antheridiophore has an erect stalk which is about 2-3 cm in length. The top of antheridiophore is a flattened, slightly convex; eight lobed pelate discs each lobe of the disc has a growing point at its tip and this represent the apex of branch. On each lobe of the pellate disc, 10-12 antheridia develop in acropetl succession is the oldest being near the center and the youngest towards the tips of lobe. The ventral surface of stalk of antherodiosphore bears the scale and the rhizoids along the two grooves. The internal structure of antheridiospore is similar to that of the thallus. The antheridial chamber open outside by the pores called ostioles.
Structure of mature antheridium:
The mature antheridium is club shape structure and consists of a short multicellular and rounded or ovoid antheridium proper. The antheridium proper has a single jacket. The jacket layer encloses the single androcytes. The androcytes gets metamorphosed into motile biflagellated antherozoids or male gametes.
Dehiscence of the antheridium:
The mature antheridium dehiscence in the presence of water. When the water enter into the antheridial chamberthrough the outside, the antheridium become swell up. Some of the terminal cells the wall on coming in contact with water disintegrated. Thus the antheridium raptureand the mass of the antherozoid emerge out. The antherozoids are sets free from the mass and swim in water. Each antherozoid is long slightly coiled rod shaped st. with two flagella attach to the anterior end. The antherozoids swims in water present in the grooves of receptacles with the help of flagella.
The archegoniospore consists of slender stalk and female receptacle. The stalks of mature archegoniosphore are comparatively longer and stouter then the antheridiospphore. The stalk is about 5-7cm in long and each surmounted by the lobe disc called the female receptacle. The disc is eight lobed with nine umbrellaslike rays dropping down.
All the archegonia are covered by the two-lipped membrane known as perichaetium or involucre. A cup shaped outgrowth that surround the archegonium called perigynium, give the protection to the archegonium.
Structure of the mature archegonium:
The mature archegonium is flask shaped structure developed on short stalk. It has swollen venter and long neck. The neck consists of the six vertical rows of jacket cells. The apical parts of neck consistof four covered cells or lid cells. A single layer of jackets surrounds the venter. The venter has one egg and one venter canal cell. The fully mature, the neck canal cell and venter canal cell disorganize and to form the mucilage mass. Which absorb the moisture and swells. The swelling exerts the pressure on lid cells so that they separate apart and the passage down to the egg is developed.
It takes place in presence of water. The mucilage with the malic acids starts oozing through the mouth and that attract the antherozoids. The movement of the antherozoid in response of chemical is called chemotaxis. During the fertilization the antherozoids moving into water with female receptacle. Then a no. Of antherozoids enter the archegonium, but only one of them fuses with the egg to form the diploid zygote. The zygote developed the wall around itself and called the oospore. The fertilized egg or oospores represent the first stage of sporophytic generation.
After the fertilization the archegonial cells shrivels. The wall of venter gives the 1-4 layered investment called calyptra which is of the gametophytic origin. In addition, perigynium also grows rapidly and covers the calyptra. The third covering called the involucre or perichetium is already present around the archegonia of each lobe. Thus the mature sporophyte is enveloped by three distinct protective covering; thecalyptra, the perigynium, the perichaetium. These three covering layer protect young sporogonium from desiccation. The mature sporogonium of marchantia is completely parasite on gametophyte because of the lack of chloroplast; ventral position and the covering layer avoid the light penetration. It is differentiated into foot, seta and capsule:
1. Foot: it is made up of parenchymatous cells, which are situated towards the base of archegonium .It helps in absortion of food material from the gametophyte for developing sporophyte.
2. Seta: the seta is short stalked, junction of connecting link between the foot and the capsule. It helps in the dispersal of spores.
3. Capsule: it is situated towards the neck of archegonium. It has single jacket layer of cell.
Spores and germination of spores:
When the spores fall on the suitable condition they germinated. The swell by the absorption of water. The exine ruptures and intine produce the small germ tube. The filament like structure divided and redivided to form a multicellular structure and finally gets changed into dichotomously branched thallus of marchntia.
Alternation of generation:
The life cycle of marchantia shows the distict alternation of generation. The lifecycle is completed only when the plant passes through the both the stages. The dominant phase is haploid gametophytic phase. The gametophyte reproduces sexually by male and female gametes and the result in the formation of sporophyte. The sporophyte reproduces asexually by the formation of spores. These spores give rise to the gametophyte. Themarchantia plant is a gametophyte which develops from haploid sporo. The plant body consists of dorsoventrally differentiated thallus. The antheridia produce the female gametes or egg. The antherozoids swim in the water and reach to the egg of an archegonium. Out of them only one fuses with egg together to form a diploid zygote. The diploid zygote represent of first stage of sporophyteic generation. The diploid zygote develops into complicating and elaborated structure the sporogonium or sporophyte. The sporogenous cell inside the sporophyte divided by meiosis to form a tetrad of haploid. This method of spore formation involving the meiosis is an asexual reproduction. The spores gametophytic stage. Each sporegerminates and forms a haploid gametophytic thallus of marchantia.These two generation regularly alternate to each other. This is known as alternation of generation.
1. Small leafy plant, rhizoid axis leaves are present.
2. Rhizoids are only one type.
3. Presence of colmella (sterile structure).
Moss: Funaria, polytrichum
Distribution: Worldwide in distribution, cold region, moist wall, rainy season and are valvate like, dry-winter season.
Simple leafy plant 1-more cm in the length. Green in color, root like rhizoids, unicellular, branched, and only one type and helps in fixation, absorption of water mineral, stout and cylindrical stem leaves are small, membranous green with single rib, spiral manner.
It takes place by the formation of male and female gamete. The male and female gamete. The male and female female reproductive organ are antheridia and archegonia which lies in the association with sterile hair like St. called the paraphysis. The male and female reproductive organ are developed at the different branches of same plant,i.e . monoecious. The male branch has diversed leaves consisting group of antheridia at its apex which are usually arranged to yellow in color. The female branch has covered leaves usually produce the capsule as sporogonium.
Antheridia of the male branch are club and covered by the jacket like st. they encloses the androcytes, where the spermatozoids are formed which comes out after the brusting of antheridia. Each antherozoids are coiled and biflagellated.
Similarly archegonia of female branch are flask shape having narrow elongated neck with a row of neck canal cell and swollen venter. Inside the enter an oval ovum is formed. At the time of fertilization , the N.C.C degenerate to formed mucilaginous mass, which produce the a cane sugar that attract the antherozoid, and fuses with egg to form diploid zygote. The zygote soon develop a covering wall and called oospore. Thus the end of gametophytic and beguning of sporophytic phase . The oospore germinate to give rise to sporophyte or sporogonium. The sporogonium consist of 3 main part :
1. Foot: Itremain buried inside the archegonium nad absorb the food material for developing sporophyte.
2. Seta: it acts as stalk that helps in transportation of food as well as it helps in dehiscence of capsule.
3. Capsule:the capsule is pear shaped structure covered by the calyptra. It is the apical region consist of cap like uperculim with teeth like st. called the peristome, attach to the annukus. The peristome is hydrophobic in nature.
The main body of capsule supported by a solid base called the apophysis, consisting of conducting cells. The body of the capsule is covered by a single layer called the epidermis; they form a small gap called the stroma which helps in ex-change of gaseous. It consists of solid sterile tissue called columella, surrounded by the spore sac wall attach to the air chamber with trabaculee. Each spore sac bears a spore mother cell, which undergoes the meiosis and result in the formation of spores, these spore dispersed in dry season and when it gets a favourable condition it germinates. Each spore germinates to form the free filamentous st. called the protonema, which produce numerous bud called protonemal buds. These buds give to new gametophyte.
Alternation of generation:
In the life cycle of it is clearly seen that there are two phases. The gametophytic phase and sporophytic phase, or germination of oospore represents the sporophytic phaseswhereas gametophytic phase is the formation of gametophyte. These two phase alter to each other. That is called as alternation of generation.
Gametophytic phase is dominated over the sporophytic phase and gametophytic phase last for long period of time and is independed.
1. They are non-floweringplant reproduce by the formation of spores.
2. They are vascular cryptogams, due to the presence of xylem an d phloem.
3. They are terrestrial in habitat some are aquatic and epiphytic.
4. They are generally herbs and few of them are shrub.
5. The plant is sporophytic which consists of roots stems and leavesand vegetative cells are diploid, they reproduce asexually by the formation of homospore and heterospore.
6. They are recognized as the oldest group of the showing the origin from the Silurian period of geological era.
7. Spore produce gametophyte, they are green, independent and are called the prothallus, prothallus produce the gametes which aredevelop in antheridium and archegonium, they may produce in same gametophyte or different gametophyte.
8. As the result of sexual reproduction produce the zygote to form the sporophyte.
9. Alternation of generation is distinct
1. Perennial in habit, worldwide in distribution, present mainly in the high altitude and plains, cool, shady and moist places.
2. Structure: they are sporophytic. Root, stems and leaves are present. Stem is called the rhizome-horizontally creeping. They are perennial. Roots help in the absorption food, mineral, water.
3. Morphology: the plant body is sporophytic. This is green and can be differentiated root, stem and leaves. The stem is also known as rhizome, which is horizontally creeping. These rhizomes are covered by the small brown scales called ramenta. The roots arise from the rhizome. The leaf is petiolate and green feather like. The upper portion of petiole is called rachis, whichhas several leaflets or pinnae that bears many pinnules. The upper green part is called frond. The young leaves are coiled from the top and circinate. The phenomenon is called circinate venation.
In the fern reproduction takes place by vegetative and spore formation.
Vegetative reproduction: the fern multiply by fragmentation of rhizome and development of adventitious buds.
Reproduction by spores:
1. Sporophyllus: the leaves consisting of sorii are called sporophylls.
2. Trophophylls: The leaves without sorii called trophophylls.
3. Placenta: Internally fach sorus consists of parenchymatous cushion shaped papilla called placenta.
The sex organs of ferns are of two types. The sperm-producing organ, the antheridium, consists of a jacket of sterile cells with sperm-producing cells inside. Antheridia may be sunken (as in the family Ophioglossaceae and Marattiaceae) or protruding. They vary in size from those with hundreds of sperm to those with only 12 or so. The egg-producing organ, the archegonium contains one gamete (sex cell), which is always located in the lower, more or less dilated portion of,the venter. The upper part of the archegonium, the neck, consists of four rows of cells containing central neck cells. The uppermost of the neck cells are the neck canal cells; the lowest cell is the ventral canal cell, which is situated just above the egg.
Fertilization is attained by the ejection of sperm from antheridia. The sperm swim through free water toward simple organic acids released at the opening of the archegonium, the neck of which spreads apart at the apex, permitting the neck cells to be extruded and the sperm to swim in and penetrate the egg. The sperm are made up almost entirely of nuclear material, but their surface is provided with spiral bands of cilia—hairlike organs that effect locomotion. When the egg is fertilized, the base of the neck closes, and the embryo develops within the expanding.
Structure of gametophyte\Prothallus
fig ; Structure of prothallus.
It is a green, heart shaped, thin, flat shaped multicellular struture. It contain the deep notch at its anterior endbelow which lies the growing apex. Thus the prothallus is independent and its mode of nutrition is autotrophic. The prothallus of Dyopteris is monoecius. The sex organ and the rhizoids aresituated on the ventral surface of prothallus. The ventral side is in contact with the moist soil. The archegonia develop near the apical notch and the antheridia develop below the archegonia or near the posterior end while the unicellular brown tubular rhizoid is present. The antheridia appears earlier than the archegonia. Such condition of prothallus is called protandrous.
Alternation of generation:
Alternation of generation is distinct seen in fern; the sporophytic generation is dominant over the gametophytic generation. In ferns, the different generations exist as distinct individuals. The graceful fronds, or leaves, that we see adorn the sporophytes. If you look under the fronds of a mature plant, you’ll see structures where the spores are produced. The spores are cast from these structures onto the ground, where they develop into gametophytes. The gametophytes are tiny heart-shaped structures that are nearly invisible to the naked eye. They require a moist environment to develop and, once mature, produce sperm and egg. Like the mosses, the sperm require water to swim to the eggs, with each fertilized egg developing into the familiar, frond-bearing sporophyte.
Spermatophyte can be divided into two:
1. Gymnspermae(naked seed)
2. Angiospermae(food bearing closed seed)
General character of gymnospermae:
1. They are seed bearing plants-seed naked, not enclosed inside the fruit. Ovules produce directly in the carpel or megasporophyll, no ovary is found.
2. Oldest group of plant recorded from 300 million years back reported fossil records, some member are called as living fossil(Gingo biloba).
3. The plant is sporophyte, root,stem, leaves-2n no of chromosomes in reproductive cell and reproduce by the formation of spore which is called the microspore or pollen grain or megaspore or ovule.
4. Pollen grain is directly reached to the ovule, not on the stigma.
5. As a result of fusion of male and female gamete add form the embryo, which is polyembroyonic state and are one or more cotyledons.
6. Absence of double fertilization and triple fusion, it produce the endosperm which is a haploid in nature.
7. Most of the members are shrubs and tree, evergreen forest mostly occupies 1|3 of the world forest. Most of them are coniferous forest, xerophytic.
8. The group includesmostlyvaluableplant, timber, wood, pulp, which are the main source resin gum, tannins, and medicinal value-Taxus
9. They are advanced type, vascular tissue, vascular bundle-collateral and open type.
10. Presence of secondary growth in thickness.
11, Xylem is lacks of vessels, represented only by Tracheids.
12. Pholem is devoid of companion cells, represented by sieve tissue.
Genus: Cycas sp.
Distribution: tropical area, short shrub like or plam like st.
Structure: Sporophyte consists of root, stem, and leaves.
1. Normal tap root- much branched and deeply seated.
2. Coralloid root-positive phototrophic and negative geotrophic, symbiotic with cyanobacteria.
Stem: strout, cylindrical, trunk liker, scares of leaves.
Leaves: Pinnately compound leaves, spiral manner, large in size (macrophyllous), leaflets are thick or leathery with the pointed ends with petiole having spiny remains, crowded at the apex, scale at the apex and scales are at base of green or foliose leaves.
Plants are diocious-male and female cone are present in different branch. Amale cone, a group of male flower arranged in spiral manner on the common axis.
Fig: cycas plant
Root: the normal root of cycas consists of primary root or tap root with lateral breaches. It arises from the lower surface of the stem and is very long, positively geotrophic, its main function is fixation and absorption.
In addition to normal roots some secondary roots are develop near the surface of the ground that become negative geotrophic and grow upward and parallel to the surface. These roots are stumpy, dichotomously branched and the closed mass forming coralloid masses, above the ground and look like corals. These roots are known as coralloid roots. The internal struture of normal root and collaroidal root is same, with the only difference that only have algal zone present in the cortex of coralloid root. The algae present in the corolloid root are blue green algae like Anabaena and nostoc. These coralloid roots take part in aeration through the lenticels and the nitrogen fixation due to the present of symbiotic, endophytic blue green algae in them.
The stem of the cycas is the tuberous, when young but it becomes columnar, usually unbranched, woody stout, erect and arborescent i.e. stem bearing at the apex acrown of the leaves in apparent whorls. The stem is covered with armour or perstient leaf bases.
Leaf: The leaves in the cycas are spirally arranged around the stem. The leaves are dimorphic i.e., of the two types; foliage leaves and scaly leaves. The foliage leaves are green in color, thick, leathery, and pinnately compound and consists of three parts. They are rhomboidal shaped leafy bases, thick and woody rachis and lanceolate leaflets or pinnae.
Distribution: it is found from 1200-3300m from sea level. It is found in the eastern region and western region. Its height is about 60-100ft in coniferous forest. Pinus are:
Distribution of pinus in Nepal:
It is found in Nepal between 1800 and 3600 m, and very occasionally upto 4400 m. It is fairly widely distributed in the midland zone, between the foothills,and the main Himalayan range, where, at its lower altitude limits, it is often mixed with P. roxburghii, but in general at these altitudes, P. roxburghii will be found on south-facing slopes and P. wallichiana on north-facing slopes. It tends to be absent from the wettest parts of the midland zone. It is very characteristicof abandoned fields and grazing land. It is abundant in the inner dry valleys, such as in the Humla-Jumla, and the edges of the arid zone round Jomsom, where It is found under rainfall of 750 mm or less; it is also very common in the Solokhumbu area. Outside Nepal it extends as far as Afghanistan in the west, and Bhutan in the east, though it is absent from Sikkim.
The body of pinus is sporophytic. They have stem stem consists of two types of branches:
1. Branch of unlimited growth-Long shoot
2. Branch of limited growth- Dwarf shoot
Root: Tap root system but not deeply seated and branched. The mycorrizal roots differ from the normal roots in the following respect.
1. They are short and thick.
2. Theylack root hair.
3. Theylack root caps.
4. They are more extensively branched.
5. They are covered by the fungal hyphae.
Leaves: leaves are:
1. Primary leaves
2. Scale leaves
3. Folige leaves (needle)
Primary leaves are single, alternate (usually helically arranged), acicular leaves that are usually produced only for the first year of growth but that may be produced for many years in some species (such as Pinus quadrifolia) or may be produced on a mature plant in response to a wound. Cataphyll are alternate (helically arranged) non-chlorophyllous primary leaves produced on shoots; they are typically small, subulate or lanceolate, with erose-hyaline to ciliate margins, leaving a distinctive pattern when they fall off the shoot; they are often a useful character in identification.Needle of course, are the most common pine leaves. They are borne on dwarf shoots axillary to cataphylls in clusters or fascile of one to eight needles, initially bound together by a basal sheath that may then fall off or may persist, falling with the needles. The number of leaves per fascicle, the length of needles, the number of sides of the needles (only Pinus mononophylla has a round needle), the distribution of stomata (waxy white specks on the leaf surface), and the color and stiffness of the needles can all be useful characters for identification. The interior structure of the leaf also may be important for identification, but this requires a microscope and so leaf anatomical characters are rarely used by field workers.
Parts of pinus:
Needle: It is simply, the leaf of the pine tree. It starts its growth in dense tufts at the end of pine boughs. It is attached to its bough by a sheath or cap. There are usually three, sometimes five sections in each needle. Pine needles mature at three to five years. Many fall at maturity, but others cling to the tree, sometimes for years. The mature needles are turned brown by the summer sun, and fall from the trees in early autumn. This is the best time to collect needles for basketry, as the surface of the needle is hard and glossy and the color is rich brown. If left on the ground for a season, the needles lose their luster, become dull and brittle, and may develop dark spots from insects, mold or mildew.Vertical section needle consists of following parts
4. Mesophyll layer
Fig: v.s. of needle
Stem: the main stem or trunk is woody, erect and covered with scaly bark. It bears two types of branch; long brach and short or dwarf branches.
These are the normal branches which continue in the active growth indefinitely by means of apical buds. They are often called branches of unlimited growth.
These branches arise as buds in the axis of scale leaves at end of each year extentation of growth.
In addition of long shot, dwarf shoot arises directly from the trunk. They are also called branch of limited growth which is numerous and borne on the ordinary branches in the axis of scale leaves. The dwarf shoot consists of a short axis terminating in the cluster of green needle. It is covered with cataphylls.