C - Lublin

DEVICE FOR EVALUATION OF THE RAPE PODS CRACKING
SUSCEPTIBILITY
Rudko T., Piekarz J., Lamorski K.
Both wild and cultivated plants are characterized by natural tendency to preserve
the species, to maintain old and expand to new areas. Therefore, ripe fruits
(e.g. siliques or pods) tend to crack and shatter (sow) seeds. Among the cultivated
plants, this phenomenon is specially observed and industrially important in case of
rape because it is the reason of losses of seed yield, ranging from 3 to 20%.
Cracking susceptibility of rape has been evaluated with the use of various
methods. This phenomenon has been characterized on the base of the number of
seeds shattered on the soil surface, by the number of cracked pods or by the number
of seeds shattered into containers, placed between the rows of plants [1,4]. Another
method incorporated counting the plants that grew up from shattered seeds or
the number of cracked pods after provocative keeping the plants in the field after
reaching the full ripeness [2]. A different group has been created by direct methods,
which were originally based on determination of the force, causing the cracking
of pods. These include the simplest evaluation, consisting in squeezing the pod
in hand [10] or applying a constant force for the plants fastened in a special
threashing device [1]. The mechanism of pods cracking has been explained through
the analysis of morphological and mechanical structure of pods susceptible and
unsusceptible to cracking. The intensity of internal stresses in the pod depends on
its anatomical structure. Irregular lignification and various depths of cell walls of
internal parenchyma cause irregular drying of cells during ripening. The result of
this is the differences in tension, causing the cracking of pods. To investigate the
microstructure of pods for determination of causes of cracking, the mercury porosimetry
has been applied. The basic research work has been done with the use of
the testing machine, which was applied to disrupt the joints of pod’s valves at dissepiment
The force causing the cracking has been determined by bending the
whole pod [3]. The valve of the pod, stuck to the basis, was ripped off [5]. The
strength parameters can be described in detail when using a method consisting in
torsion of the pod by a constant angle in a testing machine [6,9]. In the methods
using the testing machine, the measurement is made difficult due to irregular
shapes of pods, different lengths, sickle-shaped bending occurring at various frequencies
and very low values of the force (about 1-2 N) causing the cracking of the
pod. A method has been elaborated, using the bending test of the pod stalk and
eliminating the above measuring difficulties and enabling to determine the value of
the force, causing the cracking of a pod [7].
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