Relationship between germination and bell pepper seed structure assessed by the X-ray test

Abstract

Alternative use of the X-ray test to evaluate seed quality has become increasingly diverse. This study was performed primarily to establish experimental procedures and verify the effectiveness of the X-ray test to detect damage or abnormalities in bell pepper (Capsicum annuum) seed structure associated with germination. Five seed lots each of hybrids Reinger and Sentinel were used. Two hundred seeds per lot were exposed to durations and intensities of X-radiation and visually classified into four categories according to the proportion between the area occupied by the embryo and endosperm in relation to the total cavity area in the internal seed structure, e.g. 0, < 50%, 50-75% and 100%. The last category was subdivided into two others based on the occurrence of morphological abnormalities. Seed samples obtained from different X-ray categories were then submitted to germination test at 25ºC for 14 days and subsequently compared with results of the X-ray analysis. Exposure to a 10 kV radiation for 260 s was the most suitable X-ray dose for visualizing seed structure. Seeds in which the area of the internal cavity occupied by the embryo and endosperm varied from 50-75% produced abnormal seedlings or did not germinate. Full seeds (100% of the internal cavity area occupied) with abnormal structure usually originated defective seedlings. As a consequence, the classification of bell pepper seeds according to the proportion occupied by the seed content (embryo + endosperm) allowed a reliable estimation of the degree of seed physical integrity based on X-ray analysis and its association with germination performance.

Relationship between eggplant seed morphology and germination

“…In Figures 3B and 3C, dark areas caused by deterioration of the radicle extremity ( Figure 3B) and the cotyledon ( Figure 3C) can be seen, and this adversely affected the germination, resulting in seedlings with a root abnormality ( Figure 3B') and an abnormal seedling ( Figure 3C'). Similar results are described for the seeds of Lithraea molleoides (Machado and Cicero, 2003) and bell pepper (Gagliardi and Marcos-Filho, 2011). From the results shown in Table 2, relating seed morphology to the results of the germination test, a small difference in the germination of seeds from the different morphological categories could be seen, when only seeds from lot 1 with lot larger area of endosperm and embryo produced a higher percentage of normal seedlings.…”

“…Therefore, for this reason, the physiological potential was responsible for their germination performance, considering that seeds with a greater filled area (category 3) gave rise to both normal and abnormal seedlings (Figure 4). Similar results were observed by Gagliardi and Marcos-Filho (2011) for bell pepper seeds, when even the undamaged seeds in some lots with an internal area completely filled by the embryo and endosperm gave rise to abnormal seedlings and non-germinated seeds. and 2, those with a smaller area occupied by embryonic seed tissues; therefore, in most cases, the physiological potential was responsible for this result and not the seed morphology.…”

“…This computer program was used to quantify the free space in bell pepper seeds, when those seeds with free spaces larger than 2.7% compared to their total area, showed a progressive reduction in normal seedling germination (Dell'Áquilla, 2007). Research done by Gagliardi and Marcos-Filho (2011) gave a similar result for the same species, where the number of abnormal seedlings increased proportionately with the increase in free space; however, the quantification of free space in this study was made visually and this can be subjective.…”

“…Examples of seeds with different internal cavity areas occupied by the embryo and endosperm can be seen in Figure 2. When the internal cavity is not completely filled by the embryo and the endosperm or contains less dense tissues, the X-ray analysis produces images with dark areas, because the resistance is not strong enough to block the passage of the X-rays (Gagliardi and Marcos-Filho, 2011).…”

“…The X-ray test has been used with various objectives including relating internal morphology to seed germination in tomatoes (Van Der Burg et al, 1994), Lithraea molleoides (Machado and Cicero, 2003), Peltophorum dubium (Oliveira et al, 2003), bell pepper (Dell'Áquilla, 2007Gagliardi and Marcos-Filho, 2011) and rice (Menezes et al, 2012).…”