Fig. 3.
Seed launching process of Orixa japonica. (A) Frontal view of the seed launching process. The horizontal digital axis indicates the time of each state in the seed launching process. The zero time in the dark blue area is when the pericarp begins to crack, and the zero time in the light blue area is when the membranous funiculus in the basal joining area is disconnected from the exocarp. The vertical digital axis indicates the height from the base of the pericarp, θ0 is the critical angle of exocarp opening at the beginning of seed launch, and θf is the opening angle of the exocarp after the seed has left the fruitlet. The red arrow indicates the basal fracture area of the exocarp. The four small inset images show details of endocarp detachment from the exocarp during the first millisecond. The four images show in turn the states of the fruit when the seed is about to be launched, when the funiculus is separated from the exocarp, when the seed is separated from the endocarp, and when the upper arms of the endocarp are separated from the exocarp. In the first small image, three coloured squares indicate different parts of the fruit (black, centre of seed; yellow, ventral base of endocarp; brown, ventral base of exocarp), which are used in C. (B) Composite image of the fruit as the seed is launched by the fruit taken from a 1000-fps video in side direction with 1-cm bar. Each image is 1 ms apart. Yellow and black dotted lines represent flight tracks of the endocarp and seed, respectively, φs is the angle between the seed’s flight direction and fruit stalk axis, and φp is the angle between the endocarp flight direction and fruit stalk axis after seed launch. (C) Changes in opening angle of the exocarp and displacements of three different parts of the fruit during seed launching. The triangles represent opening angles of the exocarp during seed launching; the coloured squares represent the displacements of different parts of the fruit indicated in A. Scale bar = 10 mm.