Radicle Length and Osmotic Stress Affect the Chilling Sensitivity of Cucumber Radicles

Cold soil and air temperatures reduce germination, seedling growth, and stand establishment of many important agronomic and horticultural crops. Chilling tolerance of many seeds is lost as they germinate and grow into young seedlings. Cucumber (Cucumis sativus cv. Poinsett 76) seedling radicles lose chilling tolerance as they emerge and elongate. Chilling at 2.5 degrees C for 72 It reduced subsequent elongation at 259 degrees C by 12,41, and 77% for 1-, 10-, and 20-mm-long radicles, respectively. Radicle elongation followed an exponential decline with increasing mannitol concentration (r(2) > 0.9) for radicles initially 1 or 10 mm in length. Chilling 1-mm radicles treated for 24 h in 0.3 or 0.6 M mannitol inhibited elongation 90 or 40%, respectively. During mannitol treatment, 0.3 and 0.6 M treated radicles increased 12.5 and 0.7 mm in length. Chilling 10-mm radicles treated for 24 h in 0.3 or 0.6 M mannitol inhibited elongation 99 or 33%, respectively. During mannitol treatment, 0.3 and 0.6 M treated radicles increased 23.8 and 1.1 nun in length. The percentage inhibition of chilling-induced radicle elongation was related to the initial radicle length when chilled by a curve of the form C-L = C-o X (1 - e(-KL)) that describes many biological reactions where the rate of change is constant and proportional to the amount of reactants present The increase in chilling-induced inhibition of radicle elongation with increasing radicle length was consistent with the progressive loss of protective compounds, possibly through dilution as the tissue expanded in volume during radicle elongation

Avaliação de biorreguladores no metabolismo secundário de beterrabas inteiras e minimamente processadas

O objetivo do trabalho foi verificar o efeito de biorreguladores em beterrabas minimamente processadas e inteiras (não processadas) sobre alguns aspectos do metabolismo secundário. Para o processamento mínimo, as beterrabas foram descascadas, sanificadas, sendo em seguida cortadas em retalhos com 2 mm de espessura, enxaguadas e centrifugadas. Nas beterrabas inteiras foram somente retiradas as folhas e os talos e sanificadas. Os tratamentos aplicados foram: etileno 1000 mL L-1, 1-metilciclopropeno (1-MCP) 300 nL L-1 e ácido salicílico 500 mg L-1. Após os tratamentos, as beterrabas foram embaladas e armazenadas a 5 ºC durante 10 dias. As injúrias causadas durante o processamento mínimo induziram o aumento na atividade da fenilalanina amônia-liase (PAL) nos tratamentos com etileno e 1-MCP e também o controle. A aplicação de ácido salicílico diminuiu a atividade desta enzima. Os tratamentos aplicados nas beterrabas minimamente processadas e inteiras não influenciaram a concentração de fenóis totais e de betalaínas, mas o teor de betalaínas foi reduzido em mais de 50% em beterraba minimamente processada em comparação com a beterraba inteira