Understanding dormancy breakage and germination ecology of Cynara cardunculus (Asteraceae)

Abstract

Summary Cynara cardunculus is a troublesome weed in temperate grazing lands. Cynara cardunculus achenes are usually dormant at dispersal and require alternating temperatures to terminate dormancy and germinate. Laboratory and glasshouse experiments were conducted to determine (i) the treatments able to terminate dormancy and (ii) the effect of environmental factors and agronomic practices on germination and emergence of non‐dormant (dry after‐ripened) achenes. Scarification, hydrogen peroxide and sodium hypochlorite promoted germination of dormant achenes. Dry after‐ripening and cold stratification were tested in two different populations. Dormancy of both populations was released from dormancy by dry after‐ripening. In contrast, cold stratification allowed dormancy release in just one of the populations, while the other was induced into secondary dormancy. Germination of non‐dormant (dry after‐ripened) achenes was maximum in a range of temperatures from 10 to 20°C and was inhibited at higher temperatures. Reduction of osmotic potential below −0.6 MPa led to a decrease in final germination. These results explain synchronic emergence of C. cardunculus seedlings in autumn after dormancy release during summer. Maximum seedling emergence was close to 60% at soil depths of 1 cm and only decreased as depth increased over 6 cm. In contrast, seedling emergence was not reduced by the presence of cover residues, while a flooding duration of 21 days was required to suppress emergence significantly. These results suggest that the deep burial of achenes and agronomic practices that take advantage of synchronic emergence of achenes could be useful tools leading to better long‐term management of C. cardunculus.

Seed Transcriptome Annotation Reveals Enhanced Expression of Genes Related to ROS Homeostasis and Ethylene Metabolism at Alternating Temperatures in Wild Cardoon

“…Maximum germination increased to day 6 and no further germination was scored until the end of the experiment. These results are in line with the previous studies using dry after-ripened wild cardoon achenes, confirming that this treatment can be used for dormancy alleviation in this plant [ 24 , 46 ].…”

“…This was performed to preserve the physiological state of achenes and to prevent ageing. To alleviate achene dormancy and to analyze the effect of different temperature regimes on dormancy termination, for all the tests performed in the present study, we used dry after-ripened achenes at 35 °C for 21 days as reported in greater detail in Huarte et al [ 24 ].…”

“…In A. thaliana the addition in the germination medium of methyl viologen, a ROS-generating compound, partially released seed dormancy, while in sunflower, it alleviated significantly dormancy activating downstream elements of the ethylene signaling pathway but without altering ABA production [ 20 , 22 , 23 ]. In wild cardoon, previous studies showed an increment of germination in the presence of H 2 O 2 [ 24 , 25 ]. On the other hand, when ROS level exceeded a certain value, the activation of antioxidant systems was observed in many species, which allows maintaining ROS homeostasis within the oxidative window for germination [ 26 ].…”

“…sylvestris (Lamk) Fiori) that is considered the progenitor of the globe artichoke [ 36 ]. Previous studies investigated the germination physiology of the wild variety, demonstrating that alternating temperatures are useful to terminate achenes dormancy causing an abrupt increase of germination percentage, especially in dry after-ripened achenes [ 24 ]. This effect was postulated to be triggered by embryo growth potential with a hormonal regulation through a reduction of gibberellins (GAs) and abscisic acid (ABA) ratio and a decrease in ABA sensitivity [ 12 , 37 ].…”

Factors Affecting Seed Germination of the Invasive Species Symphyotrichum lanceolatum and Their Implication for Invasion Success

“…In seed ecology, temperature has a dual role. It affects dormancy as well as seed germination [ 40 , 41 ]. S. lanceolatum seeds ripen in late November or early December when their dispersal begins and lasts throughout the winter.…”