Question 1: Describe Achieved

Tulips flower in spring and are pollinated by the wind or by animals. Decades of study have shown how they respond to their abiotic surroundings: they show geotropic responses and both thermonasty and photonasty, and even when cut and standing in a vase they still show geotropism and phototropism.

Define tropism and nastic response, and describe the tulip’s negative geotropism and positive phototropism, an advantage of each, and its thermonasty and photonasty.

The 2023 paper, page 2 ↗ Marking schedule, page 2 ↗

Work it out

Try it on paper first. Stuck? Take one hint at a time.

1 What is a tropism?
A growth response of a plant whose direction is set by the direction of the stimulus: growth towards it is positive, away from it negative.
2 What is a nastic response?
A reversible movement of a plant part, such as petals opening and closing, whose direction does not depend on where the stimulus comes from.
3 What are the tulip’s two tropisms, and what does each give it?
Negative geotropism: the stem grows up, away from gravity, which keeps even a cut stem standing, with its flower and leaves lifted. Positive phototropism: the stem grows towards light, so the leaves get more light for photosynthesis.
4 What are thermonasty and photonasty?
Thermonasty is a nastic response to temperature: the flower opens as it warms and closes as it cools. Photonasty is a nastic response to light: it opens in light and closes in the dark.
5 Why does warmth matter to the tulip’s pollinators?
Bees and other animal pollinators fly far more when it is warm and sunny, so that is when pollen is most likely to be carried between flowers.

Answer A tropism is a plant growth response whose direction is set by the direction of the stimulus (towards it positive, away negative). A nastic response is a reversible movement, such as petals opening and closing, whose direction does not depend on where the stimulus comes from. The tulip’s stem shows negative geotropism, growing up away from gravity, which keeps even a cut stem upright with its flower and leaves held up; it shows positive phototropism, growing towards light, so its leaves get more light for photosynthesis. Thermonasty opens the flower as it warms and closes it as it cools; photonasty opens it in light and closes it in the dark. Pollinators such as bees fly most when it is warm and sunny.

What the marker wanted

Achieved Describes, one point each: what a tropism is; what a nastic response is; either of the two nastic responses; negative geotropism, and separately what it gains; positive phototropism, and separately what it gains; and pollinators needing warmth to be active. Four make A4.

The schedule marks the question as one answer from N0 to E8. Achieved points count first: one or two give N1 or N2, three A3, four A4. Above that, two Merit points give M5 and three M6, then one Excellence point E7 and both E8.

In our words, from NZQA’s 2023 marking schedule.

Common mistake

Calling a tropism a movement, or leaving out whether it is positive or negative. A tropism is growth, and its sign says towards or away. NZQA’s 2023 report lists both among Not Achieved answers.

How did it go?

Got it moves it further out. Review brings it back tomorrow.