Transpiration, Xylem Vessels and Phloem Tubes

Cambium immature cell (could become either a xylem or phloem cell)

Tissue	Xylem	Phloem
Transport	Water an minerals from roots to shoots and leaves	Sucrose and amino acids produced in leaves during photosynthesis to every part of the plant
Process	Transpiration	Translocation
Structure	Cylindrical cells arranged end to end, in which the cytoplasm dies and the cell walls between adjoining cells breaks down leaving a dead empty tube with strengthened cell walls	Phloem tubes are made up of columns of living cylindrical cells. The cell walls between adjoining cells develop holes like a sieve allowing transport through the tube

XYLEM VESSELS: Why does the water move up? What is the “transpiration stream”?

“Water is lost through the leaf of the plant by evaporation in a process called transpiration. This results in a pull on a column of water molecules which extends right down through the stem to the roots.

Water molecules are held together by hydrogen bonds. As a water molecule evaporates from the leaf, it pulls on the water molecule next to it, which in turn exerts a pull on the water molecule next to it and so on. This transmits a pull all the way down the column of water to the root system. In addition, the water molecules also adhere to the walls of the xylem vessel, preventing gravity from pulling the molecules back down.

So as each water molecule exits the leaf, it pulls the column of water molecules upwards from the root of the plant up the xylem and into the leaf. This upward movement of water resulting from the evaporation of water from the leaf is called the transpiration stream.” (from Pass My Exams)

24/10/13

Translocation

Sucrose is glucose molecules bonded together (in a condensation reaction). Sucrose can get broken down into glucose which is used for

• releasing energy by respiration
• producing proteins, such as enzymes and chlorophyll
• producing cellulose, which strengthens the cell wall

*NOTE: Plants also need nitrates (absorbed from the soil as nitrate ions)

1. Nitrates are used to make amino acids…
2. Amino acids are needed to make proteins…
3. Proteins are used to help plant grow

ALL THE STEPS ABOVE ARE NEEDED FOR MAX. MARKS IN EXAM QS. “NITRATES HELP PLANT GROW” IS REJECTED.

Sucrose is transported to:

• shoot tip
• root tip
• fruits
• flowers (pollen production)
• etc

Transpiration the evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour from plant leaves, through the stomata

• Q: Why does more transpiration happen during the day than at night?
• A: Higher light intensity triggers stomata to open + higher temperature decreases the concentration of water vapor particles outside the leaf because heated particles have more kinetic energy and spread out away from the leaf

• Q: Suggest how plants cope with hot, dry conditions
• A: long and narrow leaf/spines/less stomata/hairs (water vapor particles passing out of the leaf clump together into droplets which attach to the hairs – this balances out the concentration gradient because the hairs are outside the leaf)

Why are there more stomata on the bottom of the leaf?

General idea: MINIMISES WATER LOSS: THE PLANT DOES NOT WANT TO LOSE WATER.

• Gas exchange would occur faster if there were more stomata on top because more sunlight hits the top (light causes stomata to open and the stomata are the site of gas exchange). If there were more stomata on top, a lot more water vapor would be lost. The plant does not want this!

Experiment to Measure the Speed of Sound in Air

1. Stand a measured distance from a building with a large, flat wall. Try to have no obstacles in the way.
2. As a trial, clap two wooden blocks together. An echo is heard: this is the clapping sound traveling to the wall and reflecting back at you. Clap repeatedly in time with the echoes (clap – echo – clap – echo etc.). Once a constant rhythm is achieved…
3. Have someone begin timing as you clap 51 times, stopping time on the 51st clap.
4. To calculate the speed of sound, divide 2x the distance to the wall by 1/50th the time for the 50 claps (the 51st is not included because that is when the stopwatch stopped timing).

Chopin “Prelude no. 15 in Db Major, Op. 28 (‘Raindrop’)”

Analysis

Form

•   This 89-bar piece is in a simple ternary form, with the A sections in the key of Db minor, and the central B section in the tonic minor, enharmonically changed to C# minor.
•   However, this ternary form is unbalanced, as the final A section is significantly shorter than the other sections and operates as little more than an extended coda.
•   The opening A section has a ternary structure of its own.
•   The piece is also unified by the incessantly repeating pedal note (Ab in the A sections, enharmonically changed to G# in the B sections), which is likely to be the rhythmic patter of the raindrops falling on Chopin‟s roof as he composed the piece.

  Melody

•   The opening theme, like Handel‟s, begins with a key-defining triad followed by a scale, though Chopin‟s triad falls and his scale rises and then falls, perhaps to add to the melancholy mood of the piece or to further signify the raindrops.
•   As a throwback to the Classical era, this opening theme is regularly phrased.
•   A second theme begins in bar 8 – another simple, sad, stepwise melody. This one is varied when it is repeated, and does not return in the final A section.
•   As the first theme returns, there is more decoration with septuplets and acciaccaturas. This is very typical of Chopin‟s piano style.
•   The B section melody is played in the left hand and is very foreboding and not particularly lyrical. The incessant raindrops almost dominate in this dark section.
•   In the short reprise of section A, the melody is broken off by the sudden interruption of a cadenza-like passage for just the right hand. Rhythm

•   The dominating rhythm is the repeating quavers of the „raindrops‟, which keep the music going despite this relatively slow tempo.
•   One aspect of rhythm that was important in Romantic music was the application of rubato, where the performer was encouraged to be flexible with the tempo in order to allow the music to „breathe‟.

  Harmony and tonality

•   The inner parts tend to support the melodies with thirds and sixths, and the harmony is often simple and diatonic, using mainly tonic and dominant seventh chords, with the occasional added ninth (e.g. bar 3, beat 2).
•   Perfect cadences continue to provide closure at important points, showing that functional tonality still applies in this early part of the Romantic period.
•   Some chromaticism appears in the second theme, and becomes more apparent in the minor key B section, along with other „melancholy‟ devices such as appoggiaturas and suspensions.
•   Other than the move to the tonic minor, modulations tend to be quite short lived, apart from the move to Ab minor and then Bb minor in the second theme. Chopin modulates by using pivot notes.
•   Pedal notes are a big feature of this piece, usually dominant pedals, and sometimes inverted (i.e. in the top part).

  Texture and piano writing

•   Chopin was a master of writing for the piano, and brings out many aspects of the instrument‟s expressive qualities, such as the use of the lower register in the middle section, and the use of the pedal. He also exploits the piano‟s ability to bring out the melody whilst keeping inner parts quieter („sotto voce‟ is a favourite instruction of Chopin‟s!).
•   The texture throughout is quite full, with three or four parts going on, and the middle of the B section is both loud and very full-textured, providing a tense and powerful climax to the piece.
•   However, Chopin also brings in stark contrasts, and frequently reduces the texture to just one or two notes.

  It is also worth drawing attention to the large number of performance instructions in this piece, ranging from dynamics, articulation and phrasing to detailed pedaling and words such as „smorzando‟. Chopin was quite precise in indicating what he wanted – a far cry from Handel‟s score.

  Section A questions

  Once again, any 30-60 second portion of the music can suffice. Questions might be something like:

1. Complete the melody in bar x.
2. What cadence can be heard in bar x?
3. What features of Romantic music can be heard in this extract?
4. How does Chopin communicate a mood of sadness in this extract?
5. What examples are there in this extract of expressive writing for the piano?
6. What is the key in bar(s) x?

Section B questions

The short answer questions are likely to be about the time or period of composition, the circumstances surrounding the composition or its acquisition of the name „Raindrop‟, or something about Chopin‟s compositions for the piano or what the name Prelude means.

The long answer question will either ask you to show how this is a typical Romantic piece, or encourage you to comment on the way Chopin uses musical elements in the Prelude, but either way a good knowledge of the chief points pertaining to each element will stand you in good stead. There is a model answer on this very piece at the end of this pack.

Mozart “Symphony no. 40 in G minor” (A Guide to the GCSE Music Set Works)

Analysis

Form

Since Classical style is all about balance, it is best to begin by looking at the form of this movement, which is the first movement in a four-movement work. Like most first movements in multi-movement works of the Classical period, this Allegro is in sonata form, which is a slightly more complex type of ABA (or ternary) form, governed particularly by the use of keys to structure the music.

Here is a clear, simple explanation of sonata form at work in this piece:

1. The “A‟ section is known as the exposition, because the main themes are “exposed‟ for the first time. In this movement, like in most sonata form pieces, there are two main themes, which we call subjects.

The first subject is in the tonic key, G minor, and begins in bar 1, without any introduction.

In bar 20 this same first subject starts to modulate, which means we are in a transition passage – a passage of music which links the first subject to the second. Some people call this a bridge passage.

In bar 44 we hear the other main theme – the second subject. This is in the relative major (B flat major), and contrasts in lots of ways with the first subject.

The exposition ends with a “winding up‟ section called a codetta – a mini version of the coda we will hear at the end of the music. Then the whole exposition is repeated.

2. The “B‟ section of the movement is called the development, because Mozart takes some time to develop (or play around with) some of the material we heard in the exposition. In this case, he concentrates entirely on the first subject and has some fun presenting it on different instruments, sometimes overlapping it with itself, and going through a lot of different, related keys. More on the keys later! The development lasts from bars 101 to 164.

3. Once Mozart has had enough playing about with the material, he “recaps‟ by giving us both subjects, and the transition, again, in a section known as the recapitulation (the returning “A‟ section if you like). However there are some big differences. 

The first subject starts the recapitulation in bar 164, as we would expect, in the tonic key of G minor.

The transition comes in again, but this time Mozart does not modulate to the dominant. Instead he moves through a number of keys (very quickly) and returns to the tonic.

In bar 227 we hear the second subject in the tonic key, which makes it sound very different as it is now a minor-key melody.

4. Finally we hear the closing section, or coda, from bar 260 to the end. One of the strengths of sonata form is that though we feel we have been on a very interesting journey, we arrive home in a very obvious and satisfying way. 

Melody

Classical music focuses heavily on melody, and Mozart himself is responsible for some of the simplest and most poignant melodies ever written.

•   The first subject begins with a three-note rhythm repeated three times, followed by a rising sixth. These two ideas are later broken up into mini „cells‟ and developed incessantly, particularly in the development section.
•   Both the first and second subjects have equal four-bar question and answer phrases, which in turn can be broken into equal two-bar phrases. This is called periodic phrasing, and is a feature of all the melodic writing in this movement.
•   Furthermore, the answering phrase, which begins in bar 5, is the same as the questioning phrase, but a tone lower. This is a sequence, and there are many examples.
•   If that is not enough, the rhythm of the melody of each two-bar phrase of this first subject is identical. How more balanced could Mozart be?
•   The second subject (bar 44) has a more laid-back feel to it, and uses a falling chromatic idea. It also has few instruments (better expressed as „reduced texture‟).
•   There is another mini-theme, a little like a second part to the second subject, which rises chromatically at bar 66.
•   The codetta focuses on just the first three notes of the first subject, and the development on these and the rising sixth idea.

  Harmony and tonality
  I mentioned in the section on form that it is the keys that structure this movement.

•   The exposition starts in the tonic (G minor) and ends in the relative major (Bb major). The modulation between these two keys happens in the transition. This is very normal for sonata form structure.
•   The recapitulation also starts in the tonic, but this time any modulations are short lived and it ends in the tonic as well. This is also normal practice.

•   The development shows Mozart‟s creative genius at work! He modulates every few bars, often by way of chromatic sequences, visiting a whole host of extremely distant keys.
•   The end of the development gives us a huge clue that the „modulation madness‟ is coming to an end and the recapitulation is around the corner – we hear a very long dominant pedal (the note D) in the closing bars of this section. This is known as dominant preparation.
•   The movement is littered with perfect cadences that give us clear signposts in this otherwise quite complex trip through tonality.
•   A lot of the harmony is chromatic, but relies on circles of fifths to underpin it. A good example of this is the answering phrase in the second subject, bars 47-50, where you can clearly see the chromaticism in the violin parts, and the circle of fifths in the „cello and bass parts.
•   It is worth noting that the harmonic rhythm – the rate at which the actual chords change underneath the melodic parts – is often quite slow, so that the melody is given room. The first subject, for instance, is set over an unchanging G minor chord for its first four bars, and then moves to a two-bar or one-bar rate of harmonic change.

  Texture and instrumentation

•   The overriding texture in this movement is melody-dominated homophony, or „melody with accompaniment‟. There are very few examples of polyphonic texture (but see „other points‟ below).
•   This does not mean that the music is textually one-dimensional. On the contrary, Mozart contrasts the instrumental texture constantly, using different combinations of instruments.
•   The woodwind gets a more prominent role than that seen in the Handel, often having melodies or sharing them with the violins, though the music is still quite string-dominated. The horns‟ role is largely textural, adding weight to the harmony.

  Other points

 Mozart includes a lot more performance instructions than Handel, such as dynamics and articulation.

 There are a number of „special effects‟ such as diminished sevenths, syncopation and short passages of counterpoint.

Section A questions

Again, pick a short extract and adapt some of the suggested questions to suit it!

1. What is the key of the extract?
2. Name the cadence heard at the end of the extract.
3. Complete the following melody/rhythm (don’t give more than five or six missing notes).
4. From which part of the sonata form structure does this extract come?
5. (For a chromatic phrase) How would you describe the melody in bar x?
6. Name two instruments which play the melody in this section.
7. How is the phrase at bar x contrasted when it is repeated in bar y?
8. What melodic/rhythmic/harmonic device can you hear in bar x?
9. How would you best describe the texture of this extract?

Section B questions

The short-answer questions in this section may ask you to identify the century or period in which the symphony was composed, or ask a question about the type of work from which this movement comes (such as how many movements the symphony has). For the longer question, focus the thinking on how Mozart uses the various elements shown above to create both balance and contrast in this movement.

Structure of a Villus

Epithelium only one cell thick so that there is short distance for active transport and diffusion

Goblet cell produces mucus which protects gut lining against digestion by body’s own enzymes

Capillary transports glucose (from carbohydrate breakdown) and amino acids (from protein breakdown)

Lacteal transports fatty acids and glycerol (from fat breakdown)

Gland lined with cells which produce digestive enzymes including maltase

Vein delivers absorbed products to the liver via the hepatic portal vein

Artery delivers blood to villi