1. Chapter 36
Plant Form

2. Parts of Vascular Plants (fig.36.1)
Consists of root and shoot systems
Both grow at their tips – shoot and root apices
Root system anchors and provides nutrition to the soil by penetrating into the soil to absorb water and ions
Shoot system consists of stems and their leaves
Leaves, flowers, fruits and seeds are formed on the shoot
Stems serve as scaffold for positioning leaves (arrangement, size and other features of leaves) decides a plant’s production of food

3. Parts of vegetative shoot
Consists of internode, node, leaf and axillary buds.
Nodes are regions where leaves are attached to stems (figure – 36.22)
Region between two nodes - internodes
An axillary bud is a lateral shoot apex that allows the plant to branch or replace the main shoot. Develop in axils (region between stem and leaf).
Reproductive phase produces flowers or floral shoots
A vegetative axillary bud has capacity to reiterate the development of primary shoot
Axillary bud – replaces the plant if munched by herbivore

4. What are the three tissues present in roots, shoots and leaves?
Dermal, ground and vascular tissues systems
Dermal tissue – epidermis is the outer protective covering. Coated with layer of wax (desert succulents)
Ground tissue – function in storage, photosynthesis and secretion (support and protection of the plant)
Vascular tissue- conducts fluids and dissolved substances throughout plant body. Xylem – conducts water and dissolved minerals and phloem – conducts a solution containing nutrients like sucrose
Wax limits water loss and ultra violet damage

5. Apical and lateral meristems fig.-36.5
Apical meristems- elongation of shoot and root apices (primary stem and root) because of repeated cell divisions
Apical meristem – three primary meristems – protoderm forms epidermis, procambium produces primary xylem and phloem, and ground meristem forms ground tissue
Lateral meristems- produce an increase in root and shoot diameter (girth)
Two lateral meristems are Cork cambium-produces outer bark of tree and vascular cambium-produces secondary vascular tissues
Older roots and shoots – secondary tissues – secondary plant body
Vascular cambium present beneath the bark

6. Dermal tissue Epidermis is covered with fatty cutin (cuticle)
Specialized cells occurring in epidermis – stomata guarded by guard cells, trichomes and root hairs
Guard cells flanking stomata regulate in passage of water and gases
stomata
Epidermis is outer protective covering of plant
Guard cells

7. Trichomes and Root hairs
Trichomes are cellular or multicellular hairlike growth of epidermis. It keeps leaves cool and reduces evaporation.
Some trichomes are glandular secreting substances that deter herbivores (figure 36.8)
Root hairs are extensions of root epidermis that help roots in absorption of water and minerals (figure 36.10).
Lateral and root hairs are different. Lateral roots are multicellular structures which originate deep within the root

8. Ground tissue Thin walled, spherical parenchyma cells (apple)
Function in storage, photosynthesis and secretion
Parenchymal cells containing chloroplasts are called Chlorenchyma

9. Collenchyma Collenchymal cells – support and protection
Present in celery- allow plant organs to bend without breaking them

10. Sclerenchyma
Sclerenchyma have thick cell walls-provide support and protection
Secondary cell walls have lignin
Fibers are long, slender cells and grouped together
Sclereids (single or in groups) – gritty nature of pears

11. What are the four zones in roots? (fig. 36.14)
Developing roots are divided into four zones
Root cap is composed of inner columella cells and outer lateral root cap cells. Protects the roots during their extension across abrasive soil particles
Zone of cell division
Zone of elongation – roots lengthen due to activity of primary meristem (longer and wider)
Zone of maturation- Cells differentiate.
Cortex differentiates to form endodermis, casparian strips has suberin produced in bands, all tissues internal to endodermis form stele (ground meristem)

12. Stems: support for above-ground organs
Stems support plants against gravity
The apical shoot meristem produces stem tissues, leaf primordia and bud primordia that develops into shoots, leaves, and flowers
Arrangement of leaves – phyllotaxy –exposure of leaves to sun
Regions where stipules fall off – leaf scars with tiny bundle scars where vascular connections were present (deciduous trees)

13. Vascular tissue arrangement in stems
Vascular bundles in monocots stems are scattered throughout ground tissue and in dicots stems the bundles are arranged in a ring (figure 32.23)
Parenchymal cells located in centre of stem – Pith
Modified stems and roots serve different specialized functions of storage and reproduction

14. What are lenticels?
In woody trees, cork cambium produces suberin impregnated cork cells (outside) and phelloderm (inside).
Cork cambium+cork+phelloderm = periderm
Lenticels are unsuberized cells of cork cambium – gaseous exchange
Lenticels

15. Leaves are main photosynthetic organs
Two basic types of leaves – microphylls and megaphylls
Microphyll is a leaf with one vein branching and megaphyll has several veins
Vein consists of xylem and phloem (vascular bundles) and are distributed throughout the leaf blade
Simple leaves have undivided blades
Compound leaves – blades are divided into leaflets (Pinnately and palmately arranged leaves – figure 36.31)
Dicots have reticulate or netted veins whereas monocots have parallel veins (figure 36.30)

16. Structure of leaf
Leaves have upper and lower epidermis with numerous stomata flanked by guard cells.
Palisade mesophyll - parenchyma is present below upper epidermis – barrel shaped to cylindrical chlorenchyma cells
Spongy mesophyll present between palisade mesophyll and lower epidermis – many interconnected air spaces with stomata – help in gas exchange and passage of water from leaves

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