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