The Study On Pod Development And Microstructure Of Pod Shattering Zone Of Common Vetch

The common vetch(Vicia sativa)is an important self-pollinating annual legume forage in high altitude area,with the advantages of wide adaptability,strong cold resistance and high nutritional value,which alleviates the problem of winter-forage lack in high altitude area and plays an irreplaceable role in grassland agriculture system in China.However,pod shattering would casue serious loss of seeds.At present,the criteria for determining the optimum harvest time of vetch seeds and the mechanism of its pod shattering have not been reported.The study,shatter-susceptible cultivar vetch of Lanjian NO.3 and shatter-resistant introduce vetch of NO.135 as the first research objects,analyzed their dynamic changes of pod and anatomical structure of ventral suture.Meanwhile,we used eight shatter-susceptible and 16 shatter-resistant vetches to analyses their differences in pod-shattering factors.The main results are as follows:1.The study on pod development and ventral suture structure of shatter-susceptible vetch cultivar Lanjian NO.3 showed that the optimal harvest time of Lanjian NO.3 seeds was the period from 25 to 30 days after peak anthesis when the pod turned to light brown.The abscission layer(AL)cells and machine tensile which generated by cells water loss were the main causes of vetch pod dehiscence.Conjecture that the thickening and fused cell walls of external valve margin cells(EVMC)were the key structures resistant to pod shattering probably.2.The study on pod development and ventral suture structure of shatter-susceptible vetch NO.135 showed that the optimum harvest time was from 26 days after peak anthesis.The key cause of the shattering-resistant trait lies in the loss of layer cells and the sclerenchymatous cells differentiated by the parenchyma cells.3.The study on comparisons and analyses of pod-shattering factors in shatter-susceptible and shatter-resistant common vetch showed that AL was an indispensable tissue in pod shattering andthe loss of AL was the key factor of pod-shatter resistance.Pod torsion force was one of the main driving force in pod shattering.The EVMC with heavily thickened secondary cell walls was the last line of defense for preventing the pod from shattering.However,there was no correlation between the pod thickness to width ratio and the pod shattering.In summary,the pod growth days and pod color were the fast and accurate criteria for determining the optimum harvest time of vetch seeds,which provided the theoretical basis for seed production.Simultaneously,we hypothesized that pod shattering was caused by the combined effect of AL,EVMC,and the pod torsion force.AL was an indispensable tissue in pod shattering and the loss of AL was the key factor of pod-shatter resistance.Machine tensile which generated by cells water loss and pod torsion force were the main driving force in pod shattering.The EVMC with heavily thickened secondary cell walls was the last line of defense for preventing the pod from shattering.Meanwhile,there was no correlation between the pod thickness to width ratio and the pod shattering.The relationship between the vetch pod shattering and the influencing factors was preliminarily determined,which laid a foundation for the further study of the vetch pod-shattering mechanism and provided theoretical support for cultivating the varieties of shatter-resistant vetch.