The present study was undertaken to understand the fruit and seed morphology, seed viability and effect of various physical and chemical factors on seed germination allowing us to explore the spread potential and/or seedling recruitment mechanism in Myriophyllum spicatum L.. The fruit of the species is a schizocarp, while as seed is a nutlet. The seed set was recorded to be ranging from 70.98-77.91% across the standing water populations, whereas no seed set was observed in running water populations due to the lack of an effective pollination system. The seed viability ranged from 85-90%. For in-vitro seed germination studies, the seeds were subjected to different physical and chemical treatments under alternate light and dark as well as continuous dark conditions. The seeds in control and those treated with different concentrations of GA3 and IAA and those whose epicarp and mesocarp were removed did not show any signs of germination. However, it was observed that surgical exposure of the embryo (cutting of hard endocarp of seed) has a promoter effect on germination and maximum percentage germination (76.66 ± 5.77) was recorded due to surgical exposure of embryo plus different concentrations of GA3. Moreover, a good germination percentage was recorded in seeds subjected to chilling treatment. Further, it was observed that seed germination of one-year-old seeds was less if compared to the current year seeds and overall percentage germination was higher in alternate light and dark if compared to continuous dark conditions in all the treatments.Thus, we conclude that the dormancy of the seeds is due to the hard endocarp and that the light has a promoting effect on germination. With the increase in the age of the seeds, there is decrease in their viability and hence germination. The chilling winter temperature of the Kashmir is responsible for breaking the hard endocarp of the seeds leading to their germination and hence spread of the populations.
The present study was undertaken to understand the fruit and seed morphology, seed viability andeffect of various physical and chemical factors on seed germination allowing us to explore thespread potential and/or seedling recruitment mechanism in Myriophyllum spicatum L.. The fruit ofthe species is a schizocarp, while as seed is a nutlet. The seed set was recorded to be ranging from70.98-77.91% across the standing water populations, whereas no seed set was observed in runningwater populations due to the lack of an effective pollination system. The seed viability ranged from85-90%. For in-vitro seed germination studies, the seeds were subjected to different physical andchemical treatments under alternate light and dark as well as continuous dark conditions. Theseeds in control and those treated with different concentrations of GA3 and IAA and those whoseepicarp and mesocarp were removed did not show any signs of germination. However, it wasobserved that surgical exposure of the embryo (cutting of hard endocarp of seed) has a promotereffect on germination and maximum percentage germination (76.66 ± 5.77) was recorded due tosurgical exposure of embryo plus different concentrations of GA3. Moreover, a good germinationpercentage was recorded in seeds subjected to chilling treatment. Further, it was observed thatseed germination of one-year-old seeds was less if compared to the current year seeds and overallpercentage germination was higher in alternate light and dark if compared to continuous darkconditions in all the treatments.Thus, we conclude that the dormancy of the seeds is due to thehard endocarp and that the light has a promoting effect on germination. With the increase in theage of the seeds, there is decrease in their viability and hence germination. The chilling wintertemperature of the Kashmir is responsible for breaking the hard endocarp of the seeds leading totheir germination and hence spread of the populations.Avaliação de parâmetros de qualidade de sementes e efeito de tratamentos físicose químicos na germinação de sementes de Myriophyllum spicatum L.ResumoO presente estudo foi realizado para compreender a morfologia do fruto e da semente, a viabilidadeda semente e o efeito de vários fatores físicos e químicos na germinação de sementes, permitindo-nosexplorar o potencial de disseminação e/ou mecanismo de mudas de recrutamento em Myriophyllumspicatum L. O fruto da espécie é um chisocarpo, enquanto a semente é uma noz. A produção desementes variou de 70,98 a 77,91% entre as populações de água paradas, enquanto que nenhumconjunto de sementes foi observado em populações de água corrente, devido à falta de um sistemaeficaz de polinização. A viabilidade das sementes variou de 85-90%. Para estudos in vitro de germinaçãodas sementes, as sementes foram submetidas a diferentes tratamentos físicos e químicos sob luz eescuridão alternadas, bem como contínuo escuro. As sementes de controle e aquelas tratados comdiferentes concentrações de GA3 e IAA e aquelas cujo epicarpo e mesocarpo foram removidosnão mostraram quaisquer sinais de germinação. No entanto, observou-se que a exposição cirúrgicado embrião (corte do endocarpo rígido de semente) tem um efeito sobre a germinação e efeitopromotor sobre a germinação e um percentual máximo (76,66 ± 5,77) foi registada por exposiçãocirúrgica do embrião a diferentes concentrações de GA3. Além disso, a percentagem de germinaçãofoi observada em sementes submetidas ao tratamento de resfriamento. Ademais, observou-se quea germinação de sementes de um ano de idade foi menor em comparação com as sementes doano corrente e a percentagem de germinação em geral foi maior quando houve luz e escuridãoalternadasse comparadas com as em condições de escuridão em todos os tratamentos. Assim, podeseconcluir que a dormência das sementes é atribuída à rigidez de endocarpo e que a luz tem um efeitopromotor sobre a germinação. Com o aumento da idade das sementes, há redução na viabilidade e,portanto, na germinação destas. A temperatura do inverno frio da Caxemira é responsável por quebraro endocarpo duro das sementes, o que leva à sua germinação e, consequentemente, à disseminaçãodas populações.