) Hormonal nature of seed responses to fluctuating temperatures in Cynara cardunculus (L.).

HUARTE H.R. AND BENECH-ARNOLD R.L.

SEED SCIENCE RESEARCH

CAMBRIDGE UNIV PRESS

Año: 2009

0960-2585

Cynara cardunculus (L.) seeds require incubation at(L.) seeds require incubation at 11 fluctuating temperatures to terminate dormancy. In thisfluctuating temperatures to terminate dormancy. In this 12 study, we analysed the physiological mechanismsstudy, we analysed the physiological mechanisms 13 underlying such a requirement, focusing on the role ofunderlying such a requirement, focusing on the role of 14 abscisic acid (ABA) and gibberellic acid (GA). As aabscisic acid (ABA) and gibberellic acid (GA). As a 15 conceptual framework, we considered the possibilityconceptual framework, we considered the possibility 16 that fluctuating temperatures and light trigger a similarthat fluctuating temperatures and light trigger a similar 17 set of hormonal processes after stimulus perception.set of hormonal processes after stimulus perception. 18 With the aim of testing this possibility, we (1) carried outWith the aim of testing this possibility, we (1) carried out 19 hydrotime analysis of germination in seeds exposedhydrotime analysis of germination in seeds exposed 20 to fluctuating temperatures (25/158C) and constantto fluctuating temperatures (25/158C) and constant 21 temperature (208C) with or without gibberellin (GA3) ortemperature (208C) with or without gibberellin (GA3) or 22 red light; (2) determined the responses of seedsred light; (2) determined the responses of seeds 23 incubated at fluctuating or constant temperature toincubated at fluctuating or constant temperature to 24 ABA, GA3, fluridone, an inhibitor of ABA biosynthesis,ABA, GA3, fluridone, an inhibitor of ABA biosynthesis, 25 and paclobutrazol, an inhibitor of GA biosynthesis; andand paclobutrazol, an inhibitor of GA biosynthesis; and 26 (3) determined the ABA content of seeds incubated at(3) determined the ABA content of seeds incubated at 27 fluctuating or constant temperature. Incubation atfluctuating or constant temperature. Incubation at 28 25/158C or 208C in the presence of GA3 reduced the25/158C or 208C in the presence of GA3 reduced the 29 mean base water potential [cb(50)] of the population tomean base water potential [cb(50)] of the population to 30 a similar extent, compared to that observed with seedsa similar extent, compared to that observed with seeds 31 incubated at 208C without the hormone. Irradiation withincubated at 208C without the hormone. Irradiation with 32 red light also reduced cb(50) to a lesser extent thanred light also reduced cb(50) to a lesser extent than 33 incubation in the presence of GA3. At all concen-incubation in the presence of GA3. At all concen- 34 trations tested, exogenously applied GA3 did nottrations tested, exogenously applied GA3 did not 35 promote germination of seeds incubated at 25/158C.promote germination of seeds incubated at 25/158C. 36 However, paclobutrazol inhibited germination,However, paclobutrazol inhibited germination, 37 suggesting that fluctuating temperatures terminatesuggesting that fluctuating temperatures terminate 38 dormancy through de novo GA biosynthesis. Fluctu-dormancy through de novo GA biosynthesis. Fluctu- 39 ating temperatures enhanced seed germination in theating temperatures enhanced seed germination in the 40 presence of ABA, but ABA content did not differpresence of ABA, but ABA content did not differ 41 between seeds incubated at fluctuating and constantbetween seeds incubated at fluctuating and constant 42 temperatures. This study provides clear evidence for the involvement of hormonal regulation in dormancy 43temperatures. This study provides clear evidence for the involvement of hormonal regulation in dormancy 4343 termination by fluctuating temperatures.