OCR GCSE Biology B (Twenty First Century)
OCR GCSE Biology B B4.4 How is plant growth controlled? Exam Questions
Free OCR GCSE Biology B exam questions for B4.4 How is plant growth controlled?, with a mark scheme for every pack. Covers plant hormones, auxin, phototropism, gravitropism, gibberellins, ethene and commercial uses of plant hormones such as rooting powder and weedkillers.
B4.4 How is plant growth controlled? exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
StemUp mark scheme flashcards
GCSE Biology Triple Science Flashcards for 2027 Onwards
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Then test yourself with the questions on this page.
From £7.99View flashcards
About OCR GCSE Biology B B4.4 How is plant growth controlled?
B4.4 explains how plants respond to their environment using hormones rather than nerves. You need to describe how auxin causes shoots to bend towards light and roots to grow downwards, and the roles of gibberellins in germination and ethene in fruit ripening. The commercial uses of plant hormones, such as selective weedkillers, rooting powders, seedless fruit and controlled ripening, are also tested. It builds on plant growth in B4.3 and contrasts with hormonal control in humans in B5.3. Examiners like describing and interpreting experiments with shoots or seedlings, including those using foil caps or mica barriers.
What you need to know
- Tropisms A tropism is a growth response to a stimulus. Phototropism is a response to light; gravitropism (geotropism) is a response to gravity.
- Auxin in shoots Light causes auxin to collect on the shaded side of a shoot. Auxin stimulates cell elongation there, so the shoot bends towards the light.
- Auxin in roots In roots, auxin collects on the lower side and inhibits elongation, so the upper side grows more and the root bends downwards.
- Gibberellins Gibberellins stimulate seed germination, stem elongation and flowering. They are used to end seed dormancy and increase fruit size.
- Ethene Ethene controls cell division and fruit ripening. Fruit can be picked unripe and ripened with ethene during transport.
- Commercial uses of auxins Auxins are used as selective weedkillers that make broad-leaved weeds grow too fast, as rooting powders for cuttings, and to promote growth in tissue culture.
Common mistakes in B4.4 How is plant growth controlled?
- Saying light destroys auxin on the light side. Auxin moves to the shaded side.
- Stating that auxin has the same effect in shoots and roots. It stimulates elongation in shoots but inhibits it in roots.
- Writing that plant hormones make cells divide faster to bend. Bending is mainly due to cell elongation on one side.
- Saying shoots grow towards light because they want light. Explain the response in terms of auxin distribution.
- Claiming selective weedkillers kill all plants. They affect broad-leaved weeds, not narrow-leaved crops such as cereals.
Try three B4.4 How is plant growth controlled? exam-style questions
1. Name the plant hormone that causes fruit to ripen. (1 mark)
Show the mark scheme answer
Ethene.
2. A shoot grew from 24 mm to 33 mm in 3 days. Calculate the mean growth rate. (2 marks)
Show the mark scheme answer
33 minus 24 = 9 mm; 9 / 3 = 3 mm per day.
3. Explain why a shoot lit from one side bends towards the light. (3 marks)
Show the mark scheme answer
Auxin moves to the shaded side of the shoot; auxin stimulates cell elongation; cells on the shaded side elongate more so the shoot bends towards the light.
B4.4 How is plant growth controlled? FAQs
What does OCR GCSE Biology B B4.4 cover?
It covers tropisms, the effects of auxin on shoots and roots, the roles of gibberellins and ethene, and commercial uses of plant hormones.
Which paper is B4.4 examined in?
J257 has two papers at each tier, Breadth in Biology and Depth in Biology, and content from any chapter, including B4, can be assessed on either one. Expect it to be linked to ideas about science and to other chapters.
What should I learn about phototropism experiments?
Know what happens to shoots with the tip removed, covered with foil or with barriers inserted, and explain each result using auxin movement and cell elongation.
