Look and listen: Xylem vessel diameter and vase life in flowering chrysanthemum

Plants transport water from the roots to the leaves through a specialized long-distance vascular network, the xylem. The xylem’s properties are important – among others – in drought and pest resilience, and vase life of cut flowers. Importantly, it currently requires destructive and time-consuming measurements to determine xylem vessel characteristics (i.e., measurements under an optical microscope), which makes it difficult to research them, or breed for an improved xylem. We have recently shown that, using an ultrasound microphone that is placed close to the stem of a dehydrating plant, it is possible to obtain sounds that – when analysed using a mathematical model – reveal information on important xylem vessel characteristics, such as xylem vessel width, length, and elasticity (Dutta et al., 2021; preprint on https://assets.researchsquare.com/files/rs-452046/v2_covered.pdf?c=1631869046). Also, a previous M.Sc. student project at HPP has shown that across a wide range of species, there is a good correlation between ultrasound- and microscope-determined xylem vessel diameter (Z. Chen, Dutta, Kaiser; unpublished). Will you be the one to take the next step in developing this method? We want you to research how well the ultrasound-based method can detect differences in xylem vessel diameter between closely related genotypes, and how well this trait links to vase life. For this, you will work with Chrysanthemum, a crop for which many cultivars exist with different durations of vase life. This work is part of the Plantenna project, a 4TU collaboration funded by NWO, where you have the chance of working in a multidisciplinary team involving researchers on plant ecophysiology (WUR) and dynamics of micro/nano systems (TU Delft). Work will be conducted at HPP, with co-supervision from TU Delft.

Used skills

You will receive several Chrysanthemum genotypes/phenotypes from Deliflor. The core part of your work will be to record ultrasound pulses from the flower stalks (shoots) of these Chrysanthemum species, and to measure their vase life, in a controlled lab environment with a commercial sensor (ultrasound microphone). Once the sound recording is done, you may (optionally) perform one or more of the following supporting measurements: (a) excising cross-sections of the shoot for xylem optical microscopy; (b) monitoring the weight of the drying flower stalk over time; (c) monitoring the water potential of the stalks in a Scholander bomb over time. Subsequently, you will analyse sound recordings per genotype, to calculate the sound emission rate and the effective xylem radii. The sound emission rate can be compared with the weight-loss (drying) pattern, or declining water potential, whereas the xylem radii can be compared with those obtained by optical imaging. While you are expected to work towards a valuable MSc thesis, the results will have a strong contribution to publications in reputed conferences/journals.

Interested in doing a BSc or MSc thesis at HPP? Please contact the HPP student coordinator Katharina Hanika.