Factors affectingCampsis radicansseed germination and seedling emergence

Abstract

The effects of environmental factors on germination and emergence of Campsis radicans seeds were examined in laboratory and greenhouse experiments. Campsis radicans pods produced numerous, papery, and small seeds (696 seeds/pod; 4 mg/seed). Seeds exhibited dormancy that was relieved (74% germination) after 2 wk of prechilling. Fluctuating temperatures and a 12-h photoperiod were required for maximum germination. Optimum conditions for C. radicans seed germination (74%) were 35/25 C (day/night, 12/12 h) with a 12-h photoperiod. Temperatures below 25/15 C or above 40/30 C were unfavorable for germination. Germination in constant temperatures or in continuous darkness was less than 15%. More than 59% of C. radicans seeds germinated at pH 5 to 9, but at pH 4 or 10 seed germination was totally inhibited. Germination was totally inhibited at osmotic stress higher than −0.2 MPa. Germination was 60% at 40 mM NaCl and 20% at 160 mM NaCl. Emergence was maximum (68%) for seeds that were placed on the soil surface, but no seedlings emerged from a soil depth at 4 cm. About 10% of seeds were still viable even after 20 wk of prechilling. Each pod contained about 700 seeds and each plant produced 20 to 40 pods. These results suggest that the spread potential of C. radicans by seeds would be at least 1,400 to 2,800 seeds plant−1. However, only seeds near the soil surface would be able to germinate.

Germinação das sementes de Conyza canadensis e Conyza bonariensis em função da disponibilidade hídrica no substrato

“…Embora nem todas as espécies sejam influenciadas na mesma extensão (Sharma, 1973;Dias Filho, 1996;Grundy 1997), estudos sobre a germinação de sementes de plantas daninhas em diferentes potenciais osmóticos têm mostrado redução na germinação total e também na velocidade de germinação à medida que é reduzida a disponibilidade de água disponível no substrato (Chachalis & Reddy, 2000;Guimarães, 2000;Silva, 2008). Em trabalho desenvolvido por Nandula et al (2006), C. canadensis mostrou-se sensível à restrição hídrica, sugerindo que a falta de água no substrato poderia ser uma ameaça à planta daninha, sendo uma possível forma de manejo dessa espécie.…”

Germinação de Borreria densiflora var. latifolia sob condições controladas de luz e temperatura

“…A germinação depende de fatores internos e externos à semente, entre os quais a água, a temperatura e o oxigênio são os mais importantes (Chachalis & Reddy, 2000). A manipulação da temperatura e da luz pode fornecer várias informações sobre o comportamento germinativo e estabelecimento de várias espécies; a temperatura altera a velocidade de absorção de água e das reações bioquímicas que acionam o metabolismo, o transporte e a ressíntese de substâncias para a plântula (Bewley e Black, 1994).…”

Effect of some environmental factors on seed germination of Eryngium caeruleum M. Bieb. populations

“…The impact of pH, from 3 up to 11, on germination of seeds of the study populations was evaluated by using the buffer solutions described by Chachalis & Reddy (2000). A 2-mM potassium hydrogen phthalate buffer solution was adjusted to pH 3 or 4 with 1 N HCl.…”