Most of a Tree Trunk Is Dead, and That Is Exactly Why It Works
Learn why plant tissues differ from animal tissues, where apical, lateral and intercalary meristems grow, how to tell parenchyma from collenchyma and sclerenchyma, and what xylem and phloem carry.
Why is so much of a plant made of dead cells?
Because dead cells make excellent support, and support is most of what a plant needs.
A tree trunk is largely dead wood — cells whose walls thickened, whose contents disappeared, and which now do nothing but hold the tree up. They cost nothing to maintain. No food, no oxygen, no repair.
An animal has no equivalent. Every tissue in your body is living and has to be fed, which is one reason animals must keep eating and plants can stand for years on very little.
The same reasoning runs right through plant tissue. Sclerenchyma is dead and gives hardness. Xylem vessels are dead and carry water. A plant builds cheap dead scaffolding and keeps its living tissue where living work is actually done. This page covers the first part of the CBSE Class 9 Science chapter on tissues.
A tree trunk is largely dead wood — cells whose walls thickened, whose contents disappeared, and which now do nothing but hold the tree up. They cost nothing to maintain. No food, no oxygen, no repair.
An animal has no equivalent. Every tissue in your body is living and has to be fed, which is one reason animals must keep eating and plants can stand for years on very little.
The same reasoning runs right through plant tissue. Sclerenchyma is dead and gives hardness. Xylem vessels are dead and carry water. A plant builds cheap dead scaffolding and keeps its living tissue where living work is actually done. This page covers the first part of the CBSE Class 9 Science chapter on tissues.
Why do plant and animal tissues differ so much?
Because plants are fixed in one place and keep growing all their lives, while animals move and stop growing at maturity.
Three consequences follow, and they explain nearly every difference.
Plants do not move, so they need support rather than motion. Much of a plant's tissue is structural, and a great deal of it is dead — which is cheap. An animal needs contractile muscle and a rapid nervous system, both of which are living and energy-hungry.
Plants grow only at certain places, for their whole lives. Growth is restricted to regions called meristems, and it continues indefinitely. An animal grows all over its body, and growth stops when the animal is mature. So a plant has permanently dividing regions and an animal does not.
Plants need less coordination. Being rooted, a plant does not have to detect and escape from danger in a fraction of a second, so it has no nervous tissue and no muscle tissue.
Everyday evidence. A branch cut from a tree can be grafted onto another tree and go on growing; a limb removed from an animal cannot. That difference comes directly from plants keeping dividing tissue available throughout life.
Plant tissues are therefore sorted differently. They are divided first into meristematic tissue, which divides, and permanent tissue, which has stopped dividing and taken a fixed form. Animal tissues are not classified this way at all, because animals have no lifelong dividing regions of that kind.
Being dead is not a defect here. A student meeting sclerenchyma or xylem for the first time often reads dead as damaged. In a plant, a dead thick-walled cell is a finished product — the cell built the wall while it was alive, and the wall is what was wanted.
Three consequences follow, and they explain nearly every difference.
Plants do not move, so they need support rather than motion. Much of a plant's tissue is structural, and a great deal of it is dead — which is cheap. An animal needs contractile muscle and a rapid nervous system, both of which are living and energy-hungry.
Plants grow only at certain places, for their whole lives. Growth is restricted to regions called meristems, and it continues indefinitely. An animal grows all over its body, and growth stops when the animal is mature. So a plant has permanently dividing regions and an animal does not.
Plants need less coordination. Being rooted, a plant does not have to detect and escape from danger in a fraction of a second, so it has no nervous tissue and no muscle tissue.
Everyday evidence. A branch cut from a tree can be grafted onto another tree and go on growing; a limb removed from an animal cannot. That difference comes directly from plants keeping dividing tissue available throughout life.
Plant tissues are therefore sorted differently. They are divided first into meristematic tissue, which divides, and permanent tissue, which has stopped dividing and taken a fixed form. Animal tissues are not classified this way at all, because animals have no lifelong dividing regions of that kind.
Being dead is not a defect here. A student meeting sclerenchyma or xylem for the first time often reads dead as damaged. In a plant, a dead thick-walled cell is a finished product — the cell built the wall while it was alive, and the wall is what was wanted.
Where are the apical, lateral and intercalary meristems?
At the tips, at the sides, and at the base of leaves or internodes — and each produces a different kind of growth.
Meristematic cells share a common appearance: thin walls, dense cytoplasm, prominent nuclei, no vacuoles, and constant division.
Apical meristem sits at the tips of roots and shoots. It increases length, which is called primary growth.
Lateral meristem, also called cambium, lies along the sides of the stem and root. It increases girth or thickness, which is called secondary growth.
Intercalary meristem sits at the base of leaves or at the internodes, between regions of permanent tissue. It allows a part to regrow after being removed, and it is characteristic of grasses.
Everyday evidence for each.
- A tree grows taller only at the tips of its branches. A mark made on a trunk at shoulder height stays at shoulder height for the life of the tree — apical meristem lengthens the tips, not the middle.
- The same tree grows thicker every year, all the way up. That is lateral meristem.
- A lawn regrows after mowing, and sugarcane regrows after being cut back. That is intercalary meristem, and it is exactly why grasses tolerate grazing and cutting when most plants do not.
A boundary case worth knowing. Cut off the growing tip of a plant — pruning — and lengthwise growth at that point stops, while side branches develop instead. That is why hedges are trimmed to make them bushy, and it is direct evidence that height growth comes from the apical meristem alone.
Do not swap the first two. Apical increases length; lateral increases girth. Writing that lateral meristem makes the plant taller is the standard error in this section, and the tree-mark example is the quickest way to remember which is which.
Meristematic cells share a common appearance: thin walls, dense cytoplasm, prominent nuclei, no vacuoles, and constant division.
Apical meristem sits at the tips of roots and shoots. It increases length, which is called primary growth.
Lateral meristem, also called cambium, lies along the sides of the stem and root. It increases girth or thickness, which is called secondary growth.
Intercalary meristem sits at the base of leaves or at the internodes, between regions of permanent tissue. It allows a part to regrow after being removed, and it is characteristic of grasses.
Everyday evidence for each.
- A tree grows taller only at the tips of its branches. A mark made on a trunk at shoulder height stays at shoulder height for the life of the tree — apical meristem lengthens the tips, not the middle.
- The same tree grows thicker every year, all the way up. That is lateral meristem.
- A lawn regrows after mowing, and sugarcane regrows after being cut back. That is intercalary meristem, and it is exactly why grasses tolerate grazing and cutting when most plants do not.
A boundary case worth knowing. Cut off the growing tip of a plant — pruning — and lengthwise growth at that point stops, while side branches develop instead. That is why hedges are trimmed to make them bushy, and it is direct evidence that height growth comes from the apical meristem alone.
Do not swap the first two. Apical increases length; lateral increases girth. Writing that lateral meristem makes the plant taller is the standard error in this section, and the tree-mark example is the quickest way to remember which is which.
How do you tell parenchyma, collenchyma and sclerenchyma apart?
By their walls. Thin walls, corner-thickened walls, or walls thickened all over with lignin.
Parenchyma — living, thin-walled cells, loosely packed with intercellular spaces.
- Functions: storage of food and water, and general filling of space
- Chlorenchyma is parenchyma containing chloroplasts, so it makes food — this is the tissue of a green leaf
- Aerenchyma is parenchyma with large air cavities, giving buoyancy to aquatic plants
Collenchyma — living, with walls irregularly thickened at the corners and very little intercellular space.
- Function: mechanical support with flexibility, letting a part bend without breaking
- Location: leaf stalks, and just below the epidermis of young stems
Sclerenchyma — dead, with walls thickened all over by lignin, and no intercellular spaces.
- Function: hardness and stiffness, making the plant tough
- Location: nut shells, seed coats, the husk of a coconut, and the fibres of jute
Everyday evidence. The soft flesh of a potato is parenchyma packed with stored starch. The stringy threads you pull off a leaf stalk are collenchyma. The hard shell of a coconut and the fibres spun into rope are sclerenchyma.
Flexibility against rigidity is the key contrast. A leaf stalk in wind needs to bend and spring back, so it has collenchyma. A nut shell needs to resist, so it has sclerenchyma. Both are support tissue, and the difference between them is exactly the difference between bending and not bending.
Only one of the three is dead. Parenchyma and collenchyma are living; sclerenchyma is dead. That single fact answers a great many questions, and it also explains why sclerenchyma cannot store food or photosynthesise — a dead cell has no contents to do it with.
All three are permanent tissues, meaning they have stopped dividing. They were produced by meristem and then took their final form, a process called differentiation — which is the link between this section and the last.
Parenchyma — living, thin-walled cells, loosely packed with intercellular spaces.
- Functions: storage of food and water, and general filling of space
- Chlorenchyma is parenchyma containing chloroplasts, so it makes food — this is the tissue of a green leaf
- Aerenchyma is parenchyma with large air cavities, giving buoyancy to aquatic plants
Collenchyma — living, with walls irregularly thickened at the corners and very little intercellular space.
- Function: mechanical support with flexibility, letting a part bend without breaking
- Location: leaf stalks, and just below the epidermis of young stems
Sclerenchyma — dead, with walls thickened all over by lignin, and no intercellular spaces.
- Function: hardness and stiffness, making the plant tough
- Location: nut shells, seed coats, the husk of a coconut, and the fibres of jute
Everyday evidence. The soft flesh of a potato is parenchyma packed with stored starch. The stringy threads you pull off a leaf stalk are collenchyma. The hard shell of a coconut and the fibres spun into rope are sclerenchyma.
Flexibility against rigidity is the key contrast. A leaf stalk in wind needs to bend and spring back, so it has collenchyma. A nut shell needs to resist, so it has sclerenchyma. Both are support tissue, and the difference between them is exactly the difference between bending and not bending.
Only one of the three is dead. Parenchyma and collenchyma are living; sclerenchyma is dead. That single fact answers a great many questions, and it also explains why sclerenchyma cannot store food or photosynthesise — a dead cell has no contents to do it with.
All three are permanent tissues, meaning they have stopped dividing. They were produced by meristem and then took their final form, a process called differentiation — which is the link between this section and the last.
What do xylem and phloem carry, and in which direction?
Xylem carries water upward only; phloem carries food in both directions.
These two are complex permanent tissues, meaning each is made of several kinds of cell working together, and together they form the plant's vascular tissue.
Xylem
- Carries water and dissolved minerals
- From the roots upward to the stem and leaves — one direction only
- Made of tracheids, vessels, xylem parenchyma and xylem fibres
- The tracheids and vessels are dead, forming hollow tubes with thickened walls
Phloem
- Carries food, mainly dissolved sugar made in the leaves
- Both up and down the plant, to wherever food is needed — bidirectional
- Made of sieve tubes, companion cells, phloem parenchyma and phloem fibres
- Its conducting cells are living
Everyday evidence. Sugarcane stores sucrose in its stem, and that sugar was made in the leaves and moved downward by phloem — which no xylem could do. Meanwhile the water that reached those leaves travelled up from the roots through xylem.
Why the directions differ. Xylem transport is passive, driven largely by water evaporating from the leaves and pulling the column up. That pull can only act upwards, so xylem has one direction. Phloem transport requires energy from its living cells, and energy can push food either way — towards a growing root tip in one season and a swelling fruit in another.
Both are not water pipes. Only xylem carries water. Answering that phloem carries water and minerals is the commonest single error in this chapter, and the fix is to tie each to its cargo: xylem to water, phloem to food.
A useful check on any answer here. The dead tissue carries the passive load in one direction; the living tissue does the active job in two. If your answer has a dead tissue actively choosing a direction, or a living tissue restricted to one, something has been swapped.
These two are complex permanent tissues, meaning each is made of several kinds of cell working together, and together they form the plant's vascular tissue.
Xylem
- Carries water and dissolved minerals
- From the roots upward to the stem and leaves — one direction only
- Made of tracheids, vessels, xylem parenchyma and xylem fibres
- The tracheids and vessels are dead, forming hollow tubes with thickened walls
Phloem
- Carries food, mainly dissolved sugar made in the leaves
- Both up and down the plant, to wherever food is needed — bidirectional
- Made of sieve tubes, companion cells, phloem parenchyma and phloem fibres
- Its conducting cells are living
Everyday evidence. Sugarcane stores sucrose in its stem, and that sugar was made in the leaves and moved downward by phloem — which no xylem could do. Meanwhile the water that reached those leaves travelled up from the roots through xylem.
Why the directions differ. Xylem transport is passive, driven largely by water evaporating from the leaves and pulling the column up. That pull can only act upwards, so xylem has one direction. Phloem transport requires energy from its living cells, and energy can push food either way — towards a growing root tip in one season and a swelling fruit in another.
Both are not water pipes. Only xylem carries water. Answering that phloem carries water and minerals is the commonest single error in this chapter, and the fix is to tie each to its cargo: xylem to water, phloem to food.
A useful check on any answer here. The dead tissue carries the passive load in one direction; the living tissue does the active job in two. If your answer has a dead tissue actively choosing a direction, or a living tissue restricted to one, something has been swapped.
Exam tip
Exam tip: name the location as well as the function
Give location, structure and function — most marks in this chapter are split three ways, and naming the tissue alone earns one of the three.
Apical increases length; lateral (cambium) increases girth; intercalary allows regrowth at leaf bases and internodes, as in grasses.
Remember the tree-mark test: a mark on a trunk never rises, because only the tips lengthen.
Meristematic cells have thin walls, dense cytoplasm, prominent nuclei and no vacuoles.
For the three simple permanent tissues, quote the wall: parenchyma thin, collenchyma thickened at the corners, sclerenchyma thickened all over with lignin.
Only sclerenchyma is dead. Parenchyma and collenchyma are living.
Name the specialised forms: chlorenchyma photosynthesises, aerenchyma gives buoyancy.
Collenchyma gives flexibility; sclerenchyma gives rigidity — both support, differently.
Xylem carries water and minerals upward and is largely dead; phloem carries food both ways and is living. Never give water to phloem.
List the components when asked: xylem has tracheids, vessels, parenchyma and fibres; phloem has sieve tubes, companion cells, parenchyma and fibres.
And label a diagram clearly — several marks in this chapter are for identification from a figure rather than for description.
Apical increases length; lateral (cambium) increases girth; intercalary allows regrowth at leaf bases and internodes, as in grasses.
Remember the tree-mark test: a mark on a trunk never rises, because only the tips lengthen.
Meristematic cells have thin walls, dense cytoplasm, prominent nuclei and no vacuoles.
For the three simple permanent tissues, quote the wall: parenchyma thin, collenchyma thickened at the corners, sclerenchyma thickened all over with lignin.
Only sclerenchyma is dead. Parenchyma and collenchyma are living.
Name the specialised forms: chlorenchyma photosynthesises, aerenchyma gives buoyancy.
Collenchyma gives flexibility; sclerenchyma gives rigidity — both support, differently.
Xylem carries water and minerals upward and is largely dead; phloem carries food both ways and is living. Never give water to phloem.
List the components when asked: xylem has tracheids, vessels, parenchyma and fibres; phloem has sieve tubes, companion cells, parenchyma and fibres.
And label a diagram clearly — several marks in this chapter are for identification from a figure rather than for description.
Did you know
Why grass survives what other plants cannot
Mow a lawn and it grows back. Mow a flower bed and the plants are finished. The difference is one tissue in one place.
Most plants keep their growing point — the apical meristem — at the tip of the shoot. Cut the tip and lengthwise growth at that point ends. That is why pruning works, and why an animal grazing on a young sapling can kill it outright.
Grasses put a meristem at the base of each leaf instead. Cut or graze the leaf and the growing region is untouched, sitting safely at ground level, and the leaf simply pushes up again from below. That is the intercalary meristem, and it is why a lawn tolerates weekly cutting for years.
The consequences reach well beyond lawns. Cereals are grasses — rice, wheat, maize, jowar, bajra — and so is sugarcane, and so is bamboo. All of them regrow from the base after cutting or grazing, and a great many of them can be harvested repeatedly rather than replanted. Sugarcane is cut and grows again from the same stubble for several harvests.
That single placement of a growing region also explains why grasses can cover ground that grazing animals keep cropped, where taller plants with tip growth cannot establish themselves.
So the three meristems are not three names to memorise for a diagram. Where a plant keeps its dividing cells determines what can happen to it and survive — and one of those positions turned out to suit almost every crop that feeds the country.
Most plants keep their growing point — the apical meristem — at the tip of the shoot. Cut the tip and lengthwise growth at that point ends. That is why pruning works, and why an animal grazing on a young sapling can kill it outright.
Grasses put a meristem at the base of each leaf instead. Cut or graze the leaf and the growing region is untouched, sitting safely at ground level, and the leaf simply pushes up again from below. That is the intercalary meristem, and it is why a lawn tolerates weekly cutting for years.
The consequences reach well beyond lawns. Cereals are grasses — rice, wheat, maize, jowar, bajra — and so is sugarcane, and so is bamboo. All of them regrow from the base after cutting or grazing, and a great many of them can be harvested repeatedly rather than replanted. Sugarcane is cut and grows again from the same stubble for several harvests.
That single placement of a growing region also explains why grasses can cover ground that grazing animals keep cropped, where taller plants with tip growth cannot establish themselves.
So the three meristems are not three names to memorise for a diagram. Where a plant keeps its dividing cells determines what can happen to it and survive — and one of those positions turned out to suit almost every crop that feeds the country.
Exam relevance
How does plant tissue in Class 9 feed into NEET Biology later?
This page is the foundation for two Class 11 Biology chapters that NEET draws on heavily, and it introduces vocabulary that both take for granted.
Anatomy of Flowering Plants in Class 11 is essentially this page expanded. It treats the same three simple permanent tissues in detail, adds the epidermis and its stomata, and then works through the internal arrangement of tissues in a root, a stem and a leaf — for dicots and monocots separately. Questions there routinely ask you to identify a tissue from a transverse-section diagram, which is impossible without the wall descriptions learned here.
Transport in Plants in Class 11 takes the xylem and phloem of this page and makes the mechanisms quantitative — root pressure, transpiration pull, and the pressure-flow model of phloem transport. The Class 9 statement that xylem is passive and unidirectional while phloem is active and bidirectional is exactly the point those mechanisms explain.
The meristems reappear in Class 11 when secondary growth is covered: the vascular cambium and cork cambium produce the wood and bark of a tree, and annual rings are a record of lateral meristem activity.
What the questions look like. In NEET, this material appears most often as match-the-column items pairing a tissue with its location or function, and as diagram-based identification. Assertion-reason questions are common on sclerenchyma being dead and on collenchyma providing flexibility. Statement-based questions of the how many of the following are correct kind also favour this topic, because there are so many small factual pairs to get right.
How board and competitive emphasis differ. A board paper is likely to ask you to draw and label a plant tissue, or to give three differences between meristematic and permanent tissue. A NEET item is more likely to describe a wall pattern or a location and ask which tissue it is, or to pair two tissues and ask which statement about both is true — so the details of where each tissue sits matter more than a general description of what it does.
The single trap that costs the most marks. Saying that phloem carries water, or that phloem transport is one-way. Both errors come from treating xylem and phloem as a matched pair of pipes. Tie each to its cargo and its direction the moment you learn them: xylem, water, upward, dead; phloem, food, both ways, living.
A second trap worth naming. Attributing increase in height to the lateral meristem. Height comes from the apical meristem, girth from the lateral — and a question about a tree growing thicker is asking about cambium, which becomes the whole basis of secondary growth in Class 11.
Anatomy of Flowering Plants in Class 11 is essentially this page expanded. It treats the same three simple permanent tissues in detail, adds the epidermis and its stomata, and then works through the internal arrangement of tissues in a root, a stem and a leaf — for dicots and monocots separately. Questions there routinely ask you to identify a tissue from a transverse-section diagram, which is impossible without the wall descriptions learned here.
Transport in Plants in Class 11 takes the xylem and phloem of this page and makes the mechanisms quantitative — root pressure, transpiration pull, and the pressure-flow model of phloem transport. The Class 9 statement that xylem is passive and unidirectional while phloem is active and bidirectional is exactly the point those mechanisms explain.
The meristems reappear in Class 11 when secondary growth is covered: the vascular cambium and cork cambium produce the wood and bark of a tree, and annual rings are a record of lateral meristem activity.
What the questions look like. In NEET, this material appears most often as match-the-column items pairing a tissue with its location or function, and as diagram-based identification. Assertion-reason questions are common on sclerenchyma being dead and on collenchyma providing flexibility. Statement-based questions of the how many of the following are correct kind also favour this topic, because there are so many small factual pairs to get right.
How board and competitive emphasis differ. A board paper is likely to ask you to draw and label a plant tissue, or to give three differences between meristematic and permanent tissue. A NEET item is more likely to describe a wall pattern or a location and ask which tissue it is, or to pair two tissues and ask which statement about both is true — so the details of where each tissue sits matter more than a general description of what it does.
The single trap that costs the most marks. Saying that phloem carries water, or that phloem transport is one-way. Both errors come from treating xylem and phloem as a matched pair of pipes. Tie each to its cargo and its direction the moment you learn them: xylem, water, upward, dead; phloem, food, both ways, living.
A second trap worth naming. Attributing increase in height to the lateral meristem. Height comes from the apical meristem, girth from the lateral — and a question about a tree growing thicker is asking about cambium, which becomes the whole basis of secondary growth in Class 11.
Key takeaways
Plant tissues, meristems, xylem and phloem: quick revision
- Plants are fixed and grow all their lives, so much of their tissue is structural and dead — cheap support that needs no food.
- Plant tissue splits into meristematic (dividing) and permanent (differentiated). Animals have no lifelong dividing regions of this kind, and no equivalent classification.
- Plants have no muscle or nervous tissue, because a rooted organism need not move or react in a fraction of a second.
- Meristematic cells: thin walls, dense cytoplasm, prominent nuclei, no vacuoles, constantly dividing.
- Apical meristem at root and shoot tips increases length (primary growth) — a mark on a trunk never rises.
- Lateral meristem (cambium) at the sides increases girth (secondary growth).
- Intercalary meristem at leaf bases and internodes allows regrowth — which is why a lawn and sugarcane recover after cutting.
- Pruning the tip stops lengthwise growth there and makes side branches develop.
- Parenchyma: living, thin-walled, loosely packed with intercellular spaces — stores food and water. Chlorenchyma photosynthesises; aerenchyma gives buoyancy.
- Collenchyma: living, thickened at the corners — gives flexible support in leaf stalks and young stems.
- Sclerenchyma: dead, thickened all over with lignin, no intercellular spaces — gives hardness, as in nut shells, coconut husk and jute fibres.
- Only sclerenchyma is dead of the three, and that is why it cannot store food or photosynthesise.
- Xylem: carries water and minerals, upward only, and its tracheids and vessels are dead. Components: tracheids, vessels, xylem parenchyma, xylem fibres.
- Phloem: carries food, both directions, with living conducting cells. Components: sieve tubes, companion cells, phloem parenchyma, phloem fibres.
- Xylem transport is passive, driven by evaporation from leaves; phloem transport needs energy, which is why it can go either way.
- Together they form the vascular tissue, and both are complex permanent tissues.
- Phloem never carries water — tie each tissue to its cargo when you learn it.
Draw one stem in cross-section from memory and label every tissue on it, then check which you could describe by its wall alone — that is the description examiners ask for.
- Plant tissue splits into meristematic (dividing) and permanent (differentiated). Animals have no lifelong dividing regions of this kind, and no equivalent classification.
- Plants have no muscle or nervous tissue, because a rooted organism need not move or react in a fraction of a second.
- Meristematic cells: thin walls, dense cytoplasm, prominent nuclei, no vacuoles, constantly dividing.
- Apical meristem at root and shoot tips increases length (primary growth) — a mark on a trunk never rises.
- Lateral meristem (cambium) at the sides increases girth (secondary growth).
- Intercalary meristem at leaf bases and internodes allows regrowth — which is why a lawn and sugarcane recover after cutting.
- Pruning the tip stops lengthwise growth there and makes side branches develop.
- Parenchyma: living, thin-walled, loosely packed with intercellular spaces — stores food and water. Chlorenchyma photosynthesises; aerenchyma gives buoyancy.
- Collenchyma: living, thickened at the corners — gives flexible support in leaf stalks and young stems.
- Sclerenchyma: dead, thickened all over with lignin, no intercellular spaces — gives hardness, as in nut shells, coconut husk and jute fibres.
- Only sclerenchyma is dead of the three, and that is why it cannot store food or photosynthesise.
- Xylem: carries water and minerals, upward only, and its tracheids and vessels are dead. Components: tracheids, vessels, xylem parenchyma, xylem fibres.
- Phloem: carries food, both directions, with living conducting cells. Components: sieve tubes, companion cells, phloem parenchyma, phloem fibres.
- Xylem transport is passive, driven by evaporation from leaves; phloem transport needs energy, which is why it can go either way.
- Together they form the vascular tissue, and both are complex permanent tissues.
- Phloem never carries water — tie each tissue to its cargo when you learn it.
Draw one stem in cross-section from memory and label every tissue on it, then check which you could describe by its wall alone — that is the description examiners ask for.