04 Lab - Asexual propogation and tropisms WQ2024 (1)

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Feb 20, 2024

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Name / student ID Date: PLS002 WQ2024 – Lab 04 1 Objectives Many important agricultural crops are propagated asexually, i.e., vegetative propagation. In essence, asexual propagation is the production of a whole plant from a small portion of another plant (this is only possible because all living plant cells contain the full genome of the plant – totipotency). Every plant produced by vegetative propagation is genetically identical to the parent plant, i.e., it is a clone. The main objective of this lab session is to familiarize you with the theory and practice involved in plant asexual propagation ( exercises 2, 3 and 4 ). We also look at gravitropism and phototropism in exercise 1 - so you can see the response of a plant to environmental stimuli. Lab 03 – Assignments check list Pollination of tomato and fruit development with and without fertilization – For Assignment 8 data. There are no questions to answer and no points available this week, but you need to check your plants and repeat the pollination treatments. Exercise 1 Tropisms – Look at the demonstrations with your group and four questions to answer here. Exercise 2 Grafting – after the in person demonstration do your vine graft and answer three questions. Exercise 3 Cuttings – make your cuttings as described in this schedule and answer two questions Exercise 4 Tissue culture – Look at the samples provided and watch the video then answer two questions. Cucumber growth (For Assignment 10 ) You need to record the plant height, tie up your growing plant and harvest and record any fruit – number of fruit and total fruit weight. Health and safety guidance Take care not to cut yourself with the pruners, scissors and grafting tools used in this lab. Also remember the standard safety issues in glasshouses:  Wet floors - trips and slips,  Fans and lights – hair tied back  Benches (e.g. fingers between moving benches) and other snags  Electric outlets – do not get these wet Look out and take care of yourself. Label, label, LABEL! Make sure you include your section number, name/group number, date/lab number and the pot contents on the labels. Good organization, including labeling, is important in science LAB 04 PLANT PROPAGATION (GRAFTING, CUTTINGS); TROPISMS

Name / student ID Date: PLS002 WQ2024 – Lab 04 2 methodology and is the only way you will keep track of your plants. Exercise 1: Tropisms: plant response to gravity and light To illustrate the effect that light and gravity can have on plant growth, and how plants response to these various signals, tomato plants have been initially grown in pots under “standard” conditions (in greenhouse), and then placed in different conditions, or “treatments”, as follows: - In the glasshouse, one tomato plant remained upright and the other pot was tilted over on its side. - In a closed box with a hole cut in the south side, one tomato plant remained upright and the other pot was tilted over on its side. - In a tent or box without any light (complete darkness), one tomato plant remained upright and the other pot was tilted over on its side. After looking at these demonstrations in the glasshouse answer the questions below: Gravitropism 1) What happened to the plant that were tilted on its side in the dark? In particular give the rough angle that may have formed in the younger section of the stems and note which direction the stem grew in the dark. Why are the plants placed in the dark the best indication of the gravitropic response? 2) - How can bending on a stem occur in response to gravity? (Think about how a plant might “sense” gravity and alter stem growth – cell number, cell length or both & on which side of the stem). Phototropism 3) What happened to the plants that were put in different light conditions (scattered light in the glasshouse, one-directional light, no light)? Was the response different if the plant was put on its sides? In particular, note the angle that may have formed in the younger section of the stem, and whether the leaves also reoriented. 4) What is the difference between phototropism and photoperiodism (see lecture 6 PDF)? Exercise 2: Grafting Watched the demonstration of cleft grafting using parts from different grape varieties (one, the rootstock, the other, the scion) . Grafting is often performed in the winter or early spring, when both the rootstock and the scion are dormant – this type of grafting is called “bench grafting”, because it is

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