NIOS Class 12 Biology Chapter 7 Shoot System introduces the structure and functions of stems, leaves, and their modifications. Students study photosynthesis, transpiration, and adaptations related to shoots. With solved terminal exercises, answers are simplified for exam practice and revision.
This chapter helps learners understand the role of shoots in the transport and survival of plants. It strengthens the connection between plant structure and function, ensuring clarity and confidence for the NIOS Class 12 exams.
NIOS Class 12 Biology Chapter 7 Shoot System
1. Differentiate between
- (i) Dicot stem and monocot stem
- (ii) Root and stem
- (iii) Racemose and cymose inflorescence
- (iv) Stoma and hydathode
- (v) True fruit and false fruit
- (vi) Dicot and monocot leaf
(i) Dicot stem and monocot stem
| Dicot Stem | Monocot Stem |
| Epidermal hairs present | Epidermal hairs absent |
| Hypodermis is collenchymatous | Hypodermis is sclerenchymatous |
| Ground tissue is differentiated into cortex, endodermis, pericycle, pith, and medullary rays | Ground tissue is undifferentiated |
| A limited number of vascular bundles | Numerous vascular bundles |
| Uniform-sized bundles are arranged in a ring | Smaller bundles near the periphery and bigger ones are arranged in the centre |
| Vascular bundles are open | Vascular bundles are closed |
| Bundle sheath is absent | A bundle sheath is present |
| Xylem vessels are arranged in a radial row | Xylem vessels are arranged in the shape of the letter Y |
| The water cavity is absent | A water cavity is present |
| Shows secondary growth | Secondary growth is absent |
(ii) Root and stem
| Root | Stem |
| Develops from radicle | Develops from the plumule |
| Non-green due to the absence of chlorophyll | Young stems are green because of chlorophyll |
| Not divided into nodes and internodes | Divided into nodes and internodes |
| Leaves and floral buds are absent | Bear leaves, vegetative and floral buds. |
| Root cap present | No cap at the apex |
| Positively geotropic and negatively phototropic | Positively phototropic and negatively geotropic |
| Origin of lateral roots is endogenous (originating from inner layers,i.e., pericycle). | 7. Origin of lateral branches is exogenous (originating from outer layers, i.e., endodermis). |
(iii) Racemose and cymose inflorescence
| Racemose | Cymose |
| Main axis shows unlimited growth | Growth is limited |
| Axis does not terminate in a flower | Axis ends in a flower |
| Flowers occur in acropetal order (oldest flower below and youngest near the apex) | Flowers in basipetal order (terminal flower is older) |
(iv) Stoma and hydathode
| Stoma | Hydathode |
| Small | Large |
| Present throughout the leaf surface | Located only at the vein endings near the leaf margins |
| They open and close depending upon light intensity | Always remain open |
| Water loss is in the vapour form | Water comes out in liquid form and contains dissolved salts & sugars |
| Present in plants occurring in all climates | Found in plants of humid areas |
| Performs transpiration | Performs guttation |
(v) True fruit and false fruit
- A true fruit is a ripened ovary that develops after fertilization. Ovules develop into seeds, and the ovary wall matures into the fruit wall, which is now called the pericarp.
- Sometimes, along with the ovary, other floral parts like the thalamus, receptacle, or calyx may develop as part of the fruit; such fruits are called false fruits. e.g., apple, pear (thalamus), fig (receptacle).
(vi) Dicot and monocot leaf
| Dicot Leaf | Monocot Leaf |
| Stomata occur generally in the lower epidermis | Stomata are seen on both the upper and lower epidermis |
| Bulliform cells absent | Bulliform cells are present in the upper epidermis |
| Mesophyll is differentiated into palisade and spongy parenchyma | Mesophyll contains only spongy parenchyma |
| The vascular system is present as a network | Vascular systems are in rows |
| Large vascular bundle in the midrib, and the other ones decrease in size towards the leaf margin | Large vascular bundles in the midrib, but other bundles are small, generally the same size. |
2. Explain the different types of underground modified stems.
- 1. Rhizome: Thick, fleshy, horizontally growing stem near the soil surface. Bears scale leaves on nodes, terminal and axillary buds, and adventitious roots. Eg. Ginger (Adrak)
- 2. Corm: Fleshy, spherical stem with flattened base, grows vertically; bears many scale leaves, distinct nodes and internodes, buds, and adventitious roots. E.g., Saffron (‘kesar’), Yam, Gladiolus.
- 3. Bulb: Reduced, flattened discoid stem with crowded nodes bearing overlapping fleshy (inner) and dry (outer) scale leaves. Terminal bud (in centre) forms foliage (green) leaves. Adventitious roots grow from a discoid base. Eg. Onion
- 4. Tuber: Swollen tips of underground lateral branches of the stem, store food as starch, bear “eyes”. Each eye is a node that bears buds and scars of scale leaves. E.g.. Potato.
3. Explain the process of secondary growth in the dicot stem.
Growth in thickness in dicot stems becomes possible due to the formation of new tissues entirely by the activity of two lateral meristems -(i) Vascular cambium and (ii) Cork cambium. These tissues thus formed are known as secondary tissues, and growth in girth is referred to as secondary growth.
(i) Activity of vascular cambium -Forms secondary vascular tissues as follows
- The strip of cambium present in the vascular bundle is called Fascicular Cambium.
- The cells of medullary rays adjoining the strip of vascular (Fascicular) cambium become meristematic and form interfascicular cambium.
- Both fascicular and inter-fascicular cambium join to form a continuous cambium ring.
- Cambium divides and adds cells on the internal side (towards the pith), which mature into secondary xylem, and cells added towards the external side (periphery ) mature into secondary phloem.
- The amount of secondary xylem produced is comparatively greater than secondary phloem.
(ii) Activity of cork cambium- Forms periderm as follows:
- Cork cambium or phellogen develops in the cortex.
- Phellogen divides and adds cells on both the inner and the outer side.
- The inner cells differentiate into phelloderm or secondary cortex, while the outer cells differentiate into phellem or cork.
- Cork cells are compactly arranged and become dead and suberized (deposition of suberin) except in regions of lenticels, where cells are loosely arranged (complementary cells) and non-suberized. It is through the lenticels that woody branches and tree trunks can undergo gaseous exchange.
- Phellogen, phelloderm, and phellem together constitute the periderm. Due to an internal increase in thickness, the periderm replaces the epidermis, becomes protective in function.
- All the dead cells lying outside the active phellogen constitute the bark.
4. Draw and label the vertical section of a dicot leaf.
5. Define the following
(a) Flower (b) Actinomorphic (c) Heterophylly (d) Phyllotaxy (e) Hypogynous (f) Parthenocarpic fruit (g) Venation.
Ans:
- Flower: A flower is a modified shoot with nodes close to each other and floral leaves arranged in successive whorls.
- Actinomorphic: When a flower can be divided into two halves through a vertical plane, it is called an actinomorphic flower.
- Heterophylly: The phenomenon where some plants have more than one type of leaf is called heterophylly.
- Phyllotaxy: Phyllotaxy is the arrangement of leaves on a stem or a branch. The orientation and arrangement of leaves is such that they get the appropriate amount of sunlight for photosynthesis.
- Hypogynous: Hypogynous flowers are those flowers that have their ovary occupying the highest position on the thalamus, with the other three whorls successively below it.
- Parthenocarpic fruit:
- Venation: Arrangement of veins and veinlets in the lamina is known as venation.
6. What is cork cambium? State its functions.
Cork cambium is a lateral meristem that produces cork towards the outside and phelloderm or secondary cortex towards the inside. It is also called phellogen. It gives rise to the cork and secondary cortex. The inner cells differentiate into phelloderm or secondary cortex, while the outer cells differentiate into phellem or cork.
7 Draw labelled diagrams of the following
- (a) Raceme and corymb inflorescence
- (b) Axile and parietal placentation
(a) Raceme and corymb inflorescence
(b) Axile and parietal placentation
8. What is a fruit? Enlist the various types of simple fleshy fruits, giving one example of each type.
A fruit is a ripened ovary that develops after fertilisation. Types of simple, fleshy fruits are,
- (i) Drupe – mango, coconut
- (ii) Berry – tomato, banana, date palm
- (iii) Pepo – cucumber, watermelon
- (iv) Hesperidium – lemon, orange
- (v) Pome – apple, pear
9. What are the edible parts of the following fruits
(a) Mango (b) Orange (c) Apple (d) Banana (e) Coconut (f) Cashew nut
Ans:
- Mango- Mesocarp
- Orange- Juicy hairs from the endocarp
- Apple- Fleshy thalamus
- Banana- Mesocarp and endocarp
- Coconut- Endosperm
- Cashewnut- Peduncle and cotyledons
10. Match the following in column A with that of column B.
| Column A | Column B |
| (a) Tendril | (i) Protection |
| (b) Stolon | (ii) Food, storage |
| (c) Thorn | (iii) Reproduction |
| (d) Tuber | (iv) Photosynthesis |
| (e) Capitulum | (v) Climbing |
| (f) Phylloclade | (vi) Sunflower |
Ans:
- (a) Tendril – (v) Climbing
- (b) Stolon – (iii) Reproduction
- (c) Thorn – (i) Protection
- (d) Tuber- (ii) Food, storage
- (e) Capitulum – (vi) Sunflower
- (f) Phylloclade – (iv) Photosynthesis
11. Name the type of modification of an underground, non-green structure bearing nodes and internodes and ‘eyes’.
Tuber
12. If a section of stem shows scattered vascular bundles that are closed, have ‘Y’ shaped xylem, and are surrounded by bundle sheath, what group of plants is it?
Monocot plant.
13. What is the region outside the phellogen known as?
Cork or phellem.
14. When the cambium is less active, which type of wood does it produce?
Late wood or summer wood.
