Free Biology NEET Video Lectures for Morphology Of Flowering Plants

00:00:39 [Music] Hello friends, I am Chubhangi Rohadi and your biology guide for today and today we will study chapter 5 morphology of flowering plants for class 11th NCERTT. Now do you know the meaning of morphology? This term stands for study of external features, study of external structures. Now when we talk about the study of morphology, I have come across many a times to the students saying that they don't like the study of morphology or they find it boring and not interesting. So I want to tell you about

00:01:30 two things that this study of external structure is very important. It forms the basis for higher studies in evolution and physiology and even in uh ecological adaptations. So we cannot do away with it. We have to study the structure then only we can proceed to the other higher branches of biology. And as far as boredom is concerned, I can assure you one thing that in today's session, I'll try my level best to drive the boredom out of the class and see to it that you don't have to mug up the

00:02:10 things. When you try to wrote memorize the things, then the chapters become boring and not interesting. So let us try to understand the logic behind the study of morphology. In this chapter, we will learn the standard definitions and standard technical terms. Now again, these things are very important when you try to classify successfully the living organisms. Then you need to know the specific standard definitions and standard terms that are used for their description. We will also learn about

00:02:45 the possible variations that are in different parts of the plants. uh these lead to the adaptations as I told you earlier. Now a plant has root, stem, leaves and flowers. So in this chapter we'll study about all these structures one by one. Let us begin with the root system. Now root. If a young student comes to you and asks you how will you define a root? What will you say? How will you help that young fellow? Uh you might be tempted to say that roots are the structures that grow underground.

00:03:25 The underground parts of the uh plant make up the root. But is this definition always correct? What about potato, turmeric, ginger, onion? You have been studying or hearing since uh junior classes that these are not roots. These are some other structures. So we cannot safely say that all the structures that are present below the ground are root. One safe definition can be that root is that part of the plant that arises from the radical of the embryo. Here you can see this is the blumule and this is the

00:04:06 radical. The root arises from the radical of the embryo. Though it is not always the case as we will see in the later course of the session that some roots also arise from parts other than the radical but yet it is one correct definition that the part that arises from the radical can be said as root. There are many different types of roots. Actually when I was uh uprooting some weeds in my garden uh earlier someday I noticed that the roots were of different kind in different plants. For example here in this plant you can see

00:04:48 that the root is fibrous. It is profusely branched and we cannot see any main root and I could not help but notice that this plant is a monocort plant. While on the other hand there were some other plants where we could see that roots were completely different. Here there was one main primary root and many lateral branches arising from this root and you can see that the plant is dic. By the way this is carrot grass. So we have ample uh points to differentiate between two kinds of roots. One is the

00:05:33 tap root here. This one that you just saw is the tap root and the other one is the fibrous root. Let us recall the uh points once again. The in the tap root the primary root is persistent and primary root beers many literal roots as you can see them here. They are mostly present in the dicords. For example, carrot or carrot grass for that matter. On the other hand, if we talk about the fibrous roots, let us see them again. In the fibrous roots, the primary root is short-lived. And many roots arise from the base of the stem. And

00:06:14 this kind of root is mostly present in the monog for example the grass. Now functions of the root system. Again you must be knowing that the roots are primarily concerned with the absorption of water and mineral from the soil. But are there other functions also? Yes. They help in providing proper anchorage to the plant. They hold the soil so that the plant can stay upright. Besides these some uh roots are modified to store reserve food material for unfavorable conditions and many roots synthesize the plant growth regulators.

00:06:58 Now what are the plant growth regulators? Plant growth regulators are the chemicals which play a very important role in regulating various growth related activities of the plants. These can be onset of dormcancy or breaking the dormcancy, absession, seed set, fruit set, fruit fall, leaf fall, elongation of the chute or elongation of the root tip. All the activities related to the growth are controlled by various plant growth regulators and some of these regulators are synthesized by the roots. Now we know that we have just said that

00:07:38 a root needs to penetrate deep down into the soil so that it can absorb water and mineral from it. Now in order to penetrate what should the structure of the root tip be? The root tip should be slender, very fine so that it can penetrate deep down and also it must be soft so that it does not get broken when it hits something hard and at the same time it should be covered with a protective covering so that it is not damaged. That means the structure of the root tip is very typical. Let us see the structure here

00:08:16 at the bottom very bottom of the uh root tip. You can see a root cap. As I just told you that this root cap is protective in nature. Its main function is to protect the root tip from the damage. Just above the root tip you can see there is the region of meristematic activity. Now in earlier classes you have studied that meristematic tissue is the tissue which is concerned with production of new cells in the body of the plants. So it leads to the growth. The growth can be in terms of gain of height or it can be in terms of gain of

00:08:53 girth. Mismatic tissue continuously produces new cells in this very region. Now what happens that the cells produced by merist stem are very small and they have a conspicuous nucleus. They have dense cytoplasm and there are many such layers of meismatic tissue uh in this region the zone of meismatic activities. Now these cells do not get any chance to grow in size. The meismatic tissue here it is just cutting off new cells. uh continuously and new cells are being formed very quickly. These cells are very small. So this is

00:09:35 not going to elongate the root but the root needs to elongate so that it can penetrate deep into the soil. For that very purpose what happens the older cells here there there will be the newer cells and these will be the older cells. These older cells they start elongating and as the cells become older the many more layers of the cells become elongated. This is the reason where actual elongation or gain of length takes place. This is the zone of elongation. So this region of elongation that helps

00:10:23 in the gain of length of the root tip. Now once the cells have elongated they start maturing and by maturation we mean differentiation. What is differentiation? Differentiation means acquisition of proper structure and function. So when the cells have elongated properly they start differentiating and acquire proper structure and function like the epidermal cells they will u produce root hairs these root hairs will be used for absorption of water and minerals and the xyllem and phium that is the vascular

00:11:03 connections will also be formed. So this is the jone zone of maturation where the older cells get mature and this is how the root tip is formed. These are the three regions of root tip. I repeat again the region of meismatic activity, region of elongation and region of maturation. We just studied that besides uh absorbing water and minerals from the soil, root perform many other functions and in some plants they are specifically modified to perform other functions. Let us see what are the root modifications

00:11:47 for. Roots are modified for the purpose of storage of food. They may also provide support and respiration. Yes, some roots are also modified to perform respiration. We will see. First, let us discuss the roots which are modified for the storage of food. This is the figure which is given in your NCA books. You can see the turnip, carrot and sweet potato. All of them are roots. These two are the tap roots and this is advantageous root. In this picture also you can see the roots of the dalia and adventicious roots of

00:12:25 the sweet potato. These are the roots that store food. Have you noticed that these are the parts of the plant that we consume in these plants and uh please notice this that we always consume that part of the plant in which the plant stores it food for that matter so that we get the energy that the plant had stored for itself. So many uh roots are modified to store food. Now there are some roots which are advantageous roots. What are advantageous roots? In the very first slide I said that most of the roots

00:13:06 arise from the radical of the plant embryo. This is the radical and it give rise to the root. But in some cases the roots also arise from parts other than radical like they may arise from the base of the stem. If this is a stem and this is the layer of soil and normal root growing here. There may be chances that sometimes some roots arise from other parts the lower parts of the stem. These structures they grow towards the soil and function as root. These roots are known as the adventicious roots. These are present in many plants.

00:14:08 When they are present at the base of the stem, they are known as the stilt roots. And when they are present higher up in the plants they are known as prop roots. So here I have picture showing the stilt roots in uh maze and sugar cane. You can see here the uh from the base of the stem the stilt roots are growing and they are growing towards the soil. And this is the very classical picture of banyan tree showing the prop roots. Now the question arises why why do we say that these are roots? They are

00:14:48 arising from the stem. They are not arising from underground parts. How can we say that they are stems and they are roots and not stems? Can you think of one reason? Yes. The reason is that they are all growing downwards towards the soil. roots are always positively geotropic but the shoots are negatively geotropic. They move away from the ground or the soil. So this makes us say that these structures which are though growing from the stem but they are roots because they are positively geotropic and the

00:15:28 function is to provide extra support for the plant. Now as I said earlier that some roots are also modified for performing respiration. This is the picture that is given in your NCERT book of pneumats. What are pneumataphors? Actually mangroves are those plants that grow in coastal saline or brackish waters and in these waters there uh and regions and habitats there the soil concentration is very high and the soil is water logged. So the plant faces lack of oxygen. In such a condition a normal root can die. So in

00:16:10 these plants pneumats are developed and they are the breeding roots. Let us see what happens. This is actual picture of pneumataphors of riseora. And you can see the pneumataphors coming out of waterloed soil to breathe. How do they breathe? They have lenticils at their tops. Lentils are very small openings uh on their tips and they help in breathing. Now this was all for the roots. We studied that roots arise from the radical. We studied the difference between fibrous root and the tap root. Then we studied the functions of the

00:16:49 root, the regions of the root tip and some of the modifications of the root. Now we will move over to the stem. How will you define a stem? If a root is a structure that originates from the radical then the stem is the structure which originates from the plumule. Again referring to the earlier diagram there was there were two structures. One was radical the other is plumule and plumule gives rise to the stem. Now stems also have nodes and inter nodes. Here in this specimen you can see these are the nodes and the portion

00:17:42 between the two successive nodes is known as inter nodes. The nodes are somewhat swollen parts and the leaves branches everything arises from the nodes. Now here in this specimen only I would like to point to a very important structure and that is the axel the leaf exel. This is the leaf exel. Uh the portion between the stem and the pitle of the leaf. This is known as the exil. A leaf exil always bears an auxiliary bud and these buds arise to form new branches. We will return to the axel and ex auxiliary birds later when we talk

00:18:27 about modifications of stems and leaves. But for the timing please remember that the portion between the pitle and the stem is known as the axel. Now we know the functions of stem. Some of them at least we know that yes they spread out the branches. Why? When the br uh branches are fully exposed to sun and water, they will get ambient conditions. The leaves will get ambient conditions to perform photosynthesis. And stems are also concerned with conduction of water, minerals and food. Water and minerals are conducted from

00:19:08 roots to upwards and taken to the leaves for carrying out photosynthesis. And then the prepared food is taken to the all of the parts of the plant and excuse me the prepared food is taken to the rest of the plant parts and it may be stored in sink organs also. So the conduction of uh the water, minerals and food is two-way conduction. Water and minerals are taken from the roots to upwards to the leaves and food is taken uh downwards to roots for storage or to some other organs of the plant. Besides these the stems also

00:19:49 provide support. Some stems are modified to provide protection and some are modified to provide vegetative propagation. How? We will see further in later slides. This brings us to the modifications of the stem. Stems are variously modified to perform many different functions. They are modified as phyoclades, cladds, stem and bulb bills. And we will now study the function of some of them. First modification that we are going to talk about is the modification for storage of food. Now we had earlier

00:20:33 talked about the potato. Potato we have studied that it is a modified stem which grows underground the uh soil in the soil and stores food. Let us see why do we say that potato is a stem. Here you can see the eyes of the potato. We all know that these eyes may bear some new shoots. Actually these eyes are the auxiliary birds and these are the nodes of this stem. The stems which store the food. They also act as organs for perination in unfavorable conditions. So here is this picture with labelings.

00:21:23 These eyes which I just showed you are the auxiliary birds and at the terminals you can see that some of them are um already budding out in the form of shoots. Then other uh stem modification is ginger. Here you can see the presence of scale leaves and collocacia. It is also a modified stem to store the food. Here as I told you earlier that these modified stems act as organs of vination to tide over unfavorable conditions. So you can see the new shoots arising from these organs. Besides uh providing as

00:22:03 organs for perination or storage of food, some of the uh stems are also modified to provide support in the form of tendrils. So climbers are we know that very very weak plants with very weak stems and they need something to cling to so that they can climb up. That's why they are known as climbers. So some stems are modified in the form of uh tendrils to provide support. They cling to any object that comes in their way. Here it a proper label diagram showing the stem tendril. Now what I want to f focus here is the position of

00:22:42 this stem tendril. Please see that this tendril is arising from the exil. Exel. I just had talked about exil in the earlier slide that the position between the pitle and the stem. Exel to uh stem tendrils which are modifications of stems always arise from the auxiliary bud. Similarly, some stems are also modified to provide protection. Here in this specimen you can see that thorns are present and why do we say that these thorns are stem modification because they are present in the axel of the leaf

00:23:34 and thorns are present to provide protection against the grazing animals the browsing animals or the children plucking the flowers. So this is a picture showing stem thorns. The thorns which are formed from the modified stem they are also present in bogan villia. Now we know about cactus where the stems are modified to perform photosynthesis. Why it happens? Because here the leaves have been modified into uh spines to reduce the rate of transpiration. So the function of photosynthesis has been taken over by the stem. it has turned

00:24:12 green and it carries out photosynthesis. Now many a times stems also serve the purpose for vegetative propagation. This is a picture of runner of grass but actually I have got a very beautiful specimen showing the runner. Please have a look at the length of this runner and this is not the complete one. I could get just this much of the specimen. Now let us see what happens. What actually is a runner here? You can see let us think uh that this is the first plant. Okay. And uh here the roots were arising from it. A lateral

00:24:54 shoot arose from it and uh developed underneath the ground. Here at this point it produced new roots and a new plant arose from this point. Again another lateral shoot developed and at some point it produced uh roots and shoots and in this manner uh along the length of the runner you can see so many plants have arisen. You can just imagine how quickly a portion of land will be captured by this growing grass through vegetative propagation. Such runners are also present in mint plants and such lateral stems are also

00:25:35 present in some aquitic plants where where they are known as offsets. So stems are the organs for vegetative propagation also. With this we have finished our talk on the stems. We studied that the stems beard nodes and inter nodes. They have exils and uh auxiliary buds uh mature into branches. Then stems are modified to perform various different functions. Now we come over to another fascinating organ the leaf. As I said earlier the leaves develop at the nodes of the stem. But how will you actually define a uh leaf?

00:26:21 Uh we cannot say that a leaf always carries out photosynthesis or is green in color because as we will see later there are some modifications where these functions and these features have been dropped. So there must be one character that defines the leaf and that character is the presence of ailary bud. Now leaves originate from the chute epical merist stem. The merist stem that is present at the aex of the chute and they are arranged in acropetal order. Acropetal means youngest at the apex. Uh

00:26:58 I will help you to break down this term. Learn it this way. A for acropetal A for apex. So youngest at the apex. This is the acropetal order. Here is this picture of uh leaf given in your NCERTT books but we will study from the specimen. So uh let us see all the features that we have discussed so far. This is a specimen from the shoot tip of a plant. Which plant is it? Can you identify? Yes, it is uh very common people. Now you can see here the leaf is arising from the stem. This is the exhilary bud a new branch has come out.

00:27:44 Again a leaf arose at the node and here in the exhilary bud. Besides the ailary bud which will grow into new branch two stipules are also present. Unfortunately here only we can see one stipule otherwise there are two stupules which are present here. Now the leaves as I said are arranged acropetely. Acropetilally means the younger leaf is at the apex while the older leaf it as the base. So this is the acropetal order. Also talking about the structure of the leaf, you can see that this expanded portion, this portion is known

00:28:29 as the lamina of the leaf and the stock which joins the leaf to the stem is known as the pitule. We have already talked about the auxiliary bud and the stipule. Now you can see that there are many veins running throughout this leaf. This is the main midri and many branches are emerging out of this mid rib. What is the function of veins? Yes, they conduct water and minerals and photosynthets in the leaf lamina but they also provide rigidity to otherwise very soft and flowy lamina. They keep it extended so that the leaf can capture

00:29:11 quite a lot of sunlight when it is available. This was about the structure of the leaves. Have you ever noticed that all leaves do not have same kind of venation? You must have seen these two kinds of leaves at least. Here in this leaf you can see there is this midrip is it visible and the other veins which are running parall to it. On the other hand, in this very leaf, you can see that there is a network of veins arising from the mid rib. These are the two kinds of venation. In the picture also you can

00:29:54 see this is parallel venation and this is net-like venation which is known as reticulate venation. So this is reticulate venation and this is parallel venation. Also these venations reticulate venation is mostly found in dicot plants while parallel venation is found in monocot plants. So just by looking at the type of leaf venation you can tell whether a plant is monocott or dicord. Remember my earlier slides where I showed that fibrous roots are born by the monocot plants. that was told by the structure of a leaf venation

00:30:41 and tabroots are present on the dicot plants. Now we come over to the next topic that is the type of leaf. Up till now we have seen uh all these leaves that I have shown you they were the simple leaves. This is the picture again of a simple leaf. Now think what will happen. You can see that there are serrations. The margin is tooth. Okay. There are small incisions on these margins. Let us draw um a picture of such a simple leaf. Suppose this is the stem. This is the ailary bud and the pitule. And here the

00:31:28 midbane, the mid rib. And this is a leaf. with serrated or toothin margin. Now what will happen if this these incisions which are present they go deep down like this then again we will say this is one leaf and these are the loes. It may also happen that these incision may be present quite deeply. So we can get a structure like this and we will say that leaf is deeply looped. What will happen in the next stage? You can all imagine and I'll draw it for you again the leave axle the mid rib and now these cuts

00:32:40 these incisions have further moved deep within they have reached the mid rim. So what will happen? We will get structures like this on the either side of the mid rib because the incisions have reached the midrip. Here you can see them. So now this makes it a compound leaf. Such a leaf is known as compound leaf. Now when you look at such a leaf, such a compound leaf, a question arises in my mind. Uh how can you tell me that this is a part of compound leaf? Actually these uh little leaf like structures are

00:33:30 now known as leaflets and the mid rib this is known as the radius. The question that arises is just by looking at this very structure, this very leaflet, any leaflet for that matter, can you tell whether is it a leaflet part of a compound leaf or a is it a simple leaf? The question arises, can you answer this question? Can you tell me just by looking at this particular leaf whether this leaflet is an actually a leaflet or a simple leaf? The answer lies in the auxiliary bud. We see that the auxiliary bud is present

00:34:18 between the attachment of pitule to the stem. If the auxiliary bud is present here then this whole structure is a compound leaf. We have seen that auxiliary birds are not present here. So this makes them the leaflets. Um I have got a specimen for you. Now you will have to tell me whether this specimen is of compound leaf or these leaves are simple leaves. I repeat my question. Just tell me about this particular leaf. Whether is it a leaflet or a compound leaf? How will you tell me is it a simple leaf or

00:35:00 compound leaf? We will again look for the auxiliary buds. Here you cannot see any auxiliary blood. Can you? But you can see the auxilary buds here. These brown structures. I hope you are able to see it. So the auxiliary bud is here. This means this whole structure is one compound leaf and these are the leaflets of this compound leaf. Let us move ahead. So we have studied that compound leaves are those in which the leaflets arise. But in this picture you can see there are two types of compound leaves.

00:35:47 uh one where the ratches or the mid rib is visible and the other where all the leaflets seem to be arising from one point at the pitule. These leaves are called as pinately compound leaves and these are the palmetly compound leaves. So there are two types of compound leaves. Pinately compound leaves and palmetly compound leaves. In the pimemetly compound leaf, leaflets are present on the common ratches that is the mid rib. For example, as in me. While in palmetry compound leaf, the leaflets are attached at a common point

00:36:23 on the patle. For example, as in silk cotton. Now we come over to the next topic and that is photaxi. Phyotaxi means the pattern of arrangement of leaves on a stem or a branch there. Have you ever noticed that leaves do not arise randomly on the stems? If you look closely, you will find there are definite patterns in which leaves are arranged. So three most common patterns are alternate, opposite and world patterns. Alternate photaxi is seen in China rose opposite in gava and world in halistonia. I have got this specimen for

00:37:07 you and can you tell me uh which plant shows which photaxi? Let us name this specimen A and this B. Can you tell me which photaxi is present where? Here you can see the leaves are arising just opposite to each other at the same node. So this is opposite photaxi. And here you can see that leaflets are arising in a zigzag manner not on the same node. One arises at one node and then the other arises at a later node. This photaxi is alternate. Now if in your exams you are asked to draw opposite alternate or

00:38:03 world photaxi will you be able to do that? Yes. But I'll show you how you can do that in very small time. If you are asked to draw the photaxi please draw only the line diagrams and don't mess up with the leaves. If you just draw the location of the pettle that will be sufficient. So this makes up for the opposite photaxi. And with another diagram you can show the alternate photaxi. And finally talking about world which seems to be most difficult to draw if you try to draw the leaves. So you can draw a node and many leaves

00:39:00 arising on it. We'll use a different colored pen so that the pit holes are visible. Here we have shown that many leaves are arising from one node and such a phloexi is known as the world one. Now as we have studied that roots and stems are modified to perform various functions so are the leaves. Leaves are also modified to perform many functions. So we will now study about the modifications of the leaf. This is the figure that is given in your NCERTT book. And in this figure we can see the three different modifications of the

00:39:49 leaves. Some leaves are modified to give support. We talked about climbers earlier. They are very weak plants and they uh in these plants tendrils are developed and these tendrils cling to any object that is nearby and use it to climb up. Now how will you differentiate between a leaf tendril and a stem tendril? We had discussed this part earlier also. If this is the stem, this is the leaf and the tendril is arising from here. This will be stem tendril. Why? We had discussed it earlier. Please try to

00:40:34 recall that it is arising from the ailary bud and axilary bud gives rise to the branch. So this is a stem tendran. But on the other hand, let us see at another diagram. If we see that a tendril is arising directly from the node, then we will say that this is a leaf tendril and it might be an auxiliary bud in its exel. So exhilary bud it is the identification mark of a leaf. Coming over to next modification we had earlier also talked about cactus where the leaves are modified into spines. Why? Because uh cactus grow in

00:41:28 very dry and aid areas where the plant tries to save every bit of water that can be saved. And so to reduce the rates of transpiration the leaves have modified into spines. And this is the structure of an onion. And here we can see that leaves have become fleshy. Why? Because they store food. Earlier also I told you that whatever part of plant we consume mostly stores the food. This was about the normal modifications and in some plants the leaves are modified to perform very special function. Can you identify this plant?

00:42:12 This is pitcher plant. It is an insectivorous plant and the leaves are modified in the shape of a pitcher. What do they do? Whenever an insect sits on the pitcher plant, it is attracted and goes inside. Now this flap is turned off covered the pitcher gets closed the insect cannot come out and this leaf will now secrete digestive juices and whole of the insect body will be digested. This is done by these plants to meet their nitrogen requirements. So this was about the leaves. We studied what are leaves? How

00:42:53 are they variously modified to perform different functions and we also studied about different types of leaves their photaxi and their venation. The next topic that we are going to cover is the inflloresence. What is inflloresence? Just as photaxi was arrangement of leaves on the stem or branch. Inflloresence is the arrangement of flowers on the floral axis. There are many types of all uh inflloresence but for the sake of simplicity uh we can divide them into two groups reimos inflloresence and simos in

00:43:31 fllororesence. Here in this picture you can see the ryimos inflloresence where the main axis continues to grow that is it shows indeterminate growth and the flowers arise literally in acropetal fashion. I had earlier also told you acrobat means youngest at the base. But you don't have to mug these things up. I'll show you a very easy way to understand and learn it. First of all, talking about the floral axis. Suppose this is the floral axis where the flowers are going to arise and this structure is known as

00:44:14 peduncle. And the stalks of these flowers they are known as pedisil peduncle and pedison. What happens in a rimos influence? This pedunk has unlimited growth. It keeps on growing without being terminated by a flower. Suppose it has grown this much in length. Now a lateral shoot will arise and it will bear a flower. The pedle will grow for some more time. Another shoot will arise here. Then pedle will grow here and the shoots will arise and bear the flowers laterally. This way many flowers will be

00:45:05 born and the fl floral stalk is yet free to grow more. Now what happens? The flower which grew earliest is the oldest one and the flowers which are followed are the younger. In this way we get that the youngest flower comes to be at the apex while the oldest flower comes to be at the base and this is the acropetal fashion or acropetal order. Now if you remember this very uh definition of reimos in floresence you will never have to mug up that flowers are born in acropetal order in rimos and fluesence.

00:45:47 I will repeat it for you. Here the pedank is keeping on growing and lateral branches are arising and bearing flowers. So in this manner the oldest flower will be at the base and this will be followed by the younger flowers at the apex. So here the fifth flower it is the youngest and first flower is the oldest. This is the ryimos in floresence. Even in your exams when you are asked to draw resimos in fluosense please don't uh draw messy diagrams bearing flowers and all. This line diagram will sufficiently explain the

00:46:28 meaning of reimos in fluoresence. Just opposite to the rimos in fllororesence is the simos in fllororesence. Resimos can be seen in snapdragon and brasa. You all must have seen mustard plant cersome. The flowers on the uh cerso plant brasa are arranged in rimmos manner. This is the pedunker and this is the pedestal. Just to remind you just opposite to uh reimos is the simos in fllororesence. So where in uh rimos we said the pedinkle showed indeterminate growth here the pedinkle must stop growing. How will it stop

00:47:13 growing? By producing a flower at its very terminal. And how will the other flowers now be born? When the first flower grows at the terminals, a later shoot develops here at the base and the second flower is grown here. Then third flower will be grown from the base of this plant. Uh this flower then another then another and this way what happens? The oldest flower comes to at the top oldest while the youngest flower reaches the base. This kind of succession is known as bessipedal succession. There can be other mechanism also. Here

00:48:14 we saw that the flowers were being born on only one side. It can happen in another way also. Suppose this was the pedanker. It got terminated with a flower. So two lateral branches will arise from this very point and each of them will be terminated by a flower. Now these two will also be flowers at the lateral branches. In this manner the oldest flower remains at the top and the youngest flowers come towards at the base. Instead of writing young and old every time I can simply write the numbers in the order in which the

00:49:00 flowers were born. So both these examples are of the simos inflloresence. Let us rewind. This is a simos in fllororesence. This picture is given in your NCERD. The main floral axis is terminating in a flower here and then shoots areing below the main axis and again terminating in the flowers. So here the main axis has limited growth that is the growth is determinate here and because of this very feature the flowers are born in basipetal order that is youngest at the base. As for ecropetal we try to remind uh remember

00:49:46 it as a forropetal a for aex here b for base and b for basip petal. So youngest flowers will be at the base in the basip petal uh succession. Again if you remember how this happened you will never have to muck things up. This was all about the inflloresence. Examples of simos in fllororesence are the tura and bogania. So in this session we'll stop here. We have covered the root the stem the leaf and some portions of influesence. In the next session, we'll study the structure of flowers, the

00:50:26 nomenclature of their uh their parts and we will learn to write the floral formulas and floral diagrams also and then we will uh learn how to describe semi-technically three families fees, lilia and solony. So uh let us try to do some exercise questions. The first question is what is meant by modification of root? What type of modification is found in banning tree, turnip and mangrove trees? After following today's lecture, I'm quite hopeful that you can answer this question. I'll give you a small

00:51:10 hint that roots which arise from any other part other than radical and or perform some functions other than absorption of water and mineral can be said to be modifications of root. You can elaborate on them and then you can always tell that banyan trees have prop roots, turnips have roots for storage and mangro trees have roots for breathing the pneumats. Next question in your NCERTT is justify the following statement on the basis of external features. The statement is underground parts of stem are not always

00:51:48 root. We had just discussed this thing that everything that grows beneath the soil is not root. It can be another structure also. So while framing your answer try to recall this point that underground stems like potato tuber have nodes inter nodes and ailary buds and these structures are not present on the roots. The next question that I would like you to do is how is a penetly compound leaf different from a palmetly compound leaf. We already discussed that in pinately compound leaf what happens

00:52:28 many leaflets arise on the mid rib all through the length of the midri. But in palately compound leaf the structure is like a palm that is many leaflets are originating from one single point and that point is the pyhold. Here the mid rib itself has already divided into many leaflets. So in competitially compound leaf all the leaflets arise at the same point on pitule. The next question is explain with sweet examples the different types of photaxi. We had just discussed opposite alternate and world photaxi.

00:53:06 When you write the answer please try to draw these types of photaxis and give proper examples. The last question is define the term inflloresence. Explain the basis for different types of inflloresence in plants. Inflloresence was the last topic that we did and we had already discussed that in fllororesence is the modified shootute which beers a group of flowers in a specific pattern. And while you try to develop the answer, please um you can use these points to differentiate between the inflloresence that is the

00:53:44 resimos and the simos that the main axis the floral axis whether it shows determinate or indeterminate growth and whether the plants are the flowers are arranged in acropetal or basipetal arrangement. Now I would like to give some questions to you to think and reflect and also write them in your copies. Differentiate between resimos and sagos in florosence. Uh I hope the discussion that we had on in fllororesence will help you to write the differences. Try to write at least two differences and give examples also.

00:54:22 Similarly differentiate between fibrous root and adventicious root. Again try to write two differences and try to give examples also. The next question is describe the modifications of stem with suitable example. We had discussed a number of stem modifications. Give proper examples while framing the answers. The last question is how do the various leaf modifications help the plant? Again write proper functions of each of the modifications. While framing the answers for biology questions, please keep in mind that you have to try

00:54:55 to write the answers in points. Write short and crisp points and if possible support your answers with L diagrams. That's all for the today's class. Thank you and in the next session we'll continue with the later portions of this chapter. Thank you. Thank you. [Music]