Force one

Tactile thresholds were assessed in non-painful body locations (back of the dominant hand, between the second and third metacarpals) with Von Frey monofilaments (Somedic Sales AB, Hörby Sweden) [78 (link)]. These filaments consist of 17 nylon hairs with rounded tips and diameters ranging from 0.14 to 1.01 mm that stimulate fine touch receptors. The filament was pushed perpendicular to the point to be explored until it bends, making three touches to ensure that the response was coincident. After several practice trials, participants were asked to close their eyes/not look at the stimulated area and to notify if they felt any tactile sensation by saying “yes” or “no”. Null stimuli were applied randomly (once every 4–5 stimuli) to check for false positive responses. In this case, participants were informed that they had perceived a null stimulus in order to refocus their attention, but response was not included for threshold calculation. Responses with a delay of more than 3s were considered as undetected. Previous studies have shown the usefulness of this procedure to measure somatosensory sensitivity in adults with CP [79 (link)].
Pressure pain thresholds (expressed in N/cm2) were measured with a digital dynamometer (Force One, Wagner Instruments, Greenwich, CT USA) with a flat rubber tip (1 cm²) in the same body locations as described above. Participants were asked to say “pain” or to raise a hand when the pressure became painful. In those cases in which the participant could not express himself with words or gestures, the response to the painful stimulus was determined by observing the behavior by a professional with experience in the daily care of the participant, according to the consensus of Backonja et al. [80 (link)]. This procedure has been successfully used for determining pain sensitivity in adults with CP [79 (link)]. Two stimuli were applied and the pressure pain threshold was taken as the mean intensity at which the participants experienced an uncomfortable sensation.

When the total soluble solids to titratable acidity ratio of fruit reached commercial harvest standards, the fruit were hand harvested by commercially trained harvesters. ‘Valencia’ trees in orchards 1 and 2 were harvested on 3 and 12 March 2020, respectively and ‘Hamlin’ were harvested on 4 December 2019. Fruit yield is expressed as total kg of fruit per tree. For each tree, at time of harvest, 20 fruit attached to the tree branches were collected by clipping the branches. Only the branches bearing single fruit at the distal position were collected. All 20 fruits were used for fruit size measurement using a handheld digital caliper to measure the equatorial length on all 20 fruits. For each fruit, FDF was measured using a digital force gauge (Force One; Wagner Instruments, Greenwich, CT). FDF determines how much force is required for the fruit to be “pulled” or detached from the tree/branch. FDF > 6 kgf [37 (link)] is considered as a fruit that is not physiologically ready to abscise, FDF ≤ 6 kgf represents a fruit that has high tendency to drop at the time of collection.