Micro and nanoscale imaging of leaf surfaces

Walker, Shaun C. (2017) Micro and nanoscale imaging of leaf surfaces. PhD thesis, University of Nottingham.

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The plant cuticle is located on most surfaces of the plant from seeds to leaves from stem to petal, this is to allow a direct interface between the plant and its environment. These cuticles act as a barrier to prevent waters loss from the plant to the environment and penetration of compounds through the cuticle, like agrochemicals and formulations. The leaf cuticle provides an ideal surface to try to penetrate agrochemicals through. The leaf surface has a larger surface area then most surfaces of the plant allowing ease of application of formulation via spraying. This makes the study of the leaf and its cuticle important, with the interaction of the formulation and the cuticle an area of interest.

The main purpose of this thesis is to investigate the applications of a relatively new imaging technique called scanning ion conductance microscopy (SICM). This new technique is utilised to image live cells with the intention to characterise the living processors on the surface. SICM has not been used to image leaf surface before, but its non-contact nature and large z axis range makes it ideal for surface analysis. The first part of this thesis is to describe the comparison of SICM with other conventional techniques used to image leaf surfaces. For example, atomic force microscopy (AFM) and scanning electron microscopy (SEM) and asses the strengths and weaknesses of the technique for leaf imaging. This was achieved by imaging various leaf surfaces and surface features like epicuticular wax (EW) crystals and stomata. Also the possible research routes for the SICM were identified and experiments conducted to ascertain the abilities to perform them. This resulted in wetting being imaged and imaging the drying of a formulation.

The other purpose of this thesis is to investigate the possibility of live leaf imaging and characterisation, and the implications of adjuvants on live leaves. This was achieved by thermal characterisation of different leaf surfaces in two states, them being live and intact (but dried). This allowed the understanding of the impact water has on the cuticle and the importance of studying live leaves. This shows that water has a plasticizing effect on the cuticle waxes, and also effects the structure of the cuticle.

AFM with scanning thermal microscope (SThM) with local thermal analysis (LTA) were also utilised to investigate the impact of two adjuvants on the surface of live leaf cuticle. These were Brij 98 and Tris (2-ethylhexyl) phosphate (TEHP), Brij 98 in a non-ionic ethoxylated surfactant, while TEHP is a phosphoric acid ester known for its properties has a plasticizer. Both AFM and LTA showed that both resulted in the plasticizing of the cuticle with the area affected showing depression in melting transition compared with that of the native leaf surface. The thesis also shows that it is possible to characterise the impact of adjuvants on live leaf cuticles.

This thesis has shown the importance of new techniques being used to image and characterise the leaf surface, showing that image wetting as a possible research route for SICM. The new techniques have resulted in new experiments being performed that provide insight into the interactions of the cuticle with formulations and components of formulations. Also the importance of water in understanding the structure of the cuticle

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Roberts, Clive
Allen, Stephanie
Keywords: AFM, SEM, SICM, leaves, leaf, Nano & Micro
Subjects: Q Science > QH Natural history. Biology > QH201 Microscopy
Faculties/Schools: UK Campuses > Faculty of Science > School of Pharmacy
Item ID: 40713
Depositing User: Walker, Shaun
Date Deposited: 17 Jul 2017 04:40
Last Modified: 07 May 2020 12:30
URI: https://eprints.nottingham.ac.uk/id/eprint/40713

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