A petal breakstrength meter for Arabidopsis abscission studies

Abstract

Background: Abscission is the regulated dropping of plant organs, such as leaves or flower petals. This process involves a break down of the cell wall between layers of cells in the abscission zone, causing the organ to become detached. The model plant Arabidopsis thaliana undergoes floral organ abscission. Various experimental methods have been used to study Arabidopsis floral organ abscission, including measuring the petal breakstrength, or the amount of force required to pull a petal from the receptacle. Petal breakstrength provides a quantitative insight into the physical integrity of the petal abscission zone.

Results: We developed a petal breakstrength meter that allows rapid data acquisition on a personal computer. We present the design of the device and show its utility in measuring Arabidopsis petal breakstrength for abscission studies.

Conclusion: This petal breakstrength meter should enable researchers to perform the petal breakstrength assay as a routine part of the characterization of environmental and genetic factors affecting abscission.

Figure 1

Petal breakstrength meter overview. (A) The petal breakstrength meter consists of a petal gripper, a sensor, electronic circuit and personal computer. (B) Close up of sensor showing 5 cm aluminum bar attached to sensor cantilever. Petal gripper is attached to the distal end of lever with a piece of braided wire. (C-E) Petal gripper (SMD grabber with 1 mm pieces of 20 gauge insulation glued to tips) in use. (C) Petal gripper is opened. (D) Grabbing onto a flower petal that is still attached to flower. (E) After pulling on the inflorescence, petal detaches from receptacle and remains in the jaws of petal gripper. (F) Assembled electronic circuit housed in an ABS plastic enclosure (lid removed).

Figure 2

Schematic of petal breakstrength electronic circuit. Pins on the PIC18F452 that were unused are not drawn. All resistors are rated at 0.25 watts and electrolytic capacitors are rated for 50 volts.

Figure 3

Picbasic program used to program PIC18F452 microcontroller in petal breakstrength meter. The code documentation comments are preceeded by apostrophes.

Figure 4

Validation of the petal breakstrength meter. (A) Linearity of standard curve of voltage observed as a function of weight. The fitted linear equation and the correlation coefficient are shown in the upper right hand corner. (B) Data from a typical petal breakstrength assay recording. A wildtype Arabidopsis stage 13 [12] flower-attached petal was gripped by the breakstrength meter petal gripper and then recording was begun. The inflorescence was pulled down (ascending voltage) until the petal was pulled out of the flower (indicated by the triangle). Following this event, the voltage fluctuates briefly due to the damped harmonic motion of the lever following petal pulling. (C) Petal breakstrength assay results. Two petals per flower were assayed from 15 wildtype Arabidopsis thaliana Columbia ecotype plants at the indicated flower positions (n = 30 petals per flower position). Bars represent mean ± standard deviation. Flower 1 is defined as the youngest flower on the inflorescence in which the flower petals are visible.

Figure 5

Perl script findforces.pl used to facilitate extraction of petal breakstrength values from a folder of petal breakstrength assay text capture files.