Effects of wetting and drying cycles on the germination of nine species of the Chihuahuan Desert

Abstract

Plants from drylands have developed strategies to germinate even in places where available humidity is sporadic with large periods of drought. Previous works determined germination of cacti species as a response to discontinuous humidity events ("seed hydration memory"). This study is aimed at assessing whether species of the Chihuahuan Desert show a seed hydration memory. Our hypothesis is that seeds of desert species can tolerate periods of dehydration after single or multiple hydration events and subsequently germinate more and faster. We evaluated nine species: Atriplex canescens, Cucurbita foetidissima, Echinocactus platyacanthus, Ferocactus pilosus, Lepidium virginicum, Lesquerella berlandieri, Nassella tenuissima, Sartwellia mexicana, and Yucca filifera, using four treatments: T1 = 24 hours hydration/5 days dehydration (HD), T2 = Three consecutive cycles of 24 hours hydration/5 days dehydration, T3 = 72 hours hydration/5 d dehydration, and T4 = Control. Echinocactus platyacanthus, N. tenuissima, F. pilosus, and L. virginicum showed higher germination with HD treatments than the control. Ferocactus pilosus and L. virginicum had the highest germination in T2, N. tenuissima in T3, E. platyacanthus in any HD treatment while Yucca filifera in the control and T2. Yucca filifera and F. pilosus had the lowest germination rate (t 50 ) in T2; E. platyacanthus in T1 and T2. The remaining species didn't show differences in t 50 between treatments. These results indicate that at least some desert species germinate more and faster after single or multiple hydration-dehydration events showing the ability of those seeds to retain, during dehydration, the physiological changes produced from seed hydration.

Seed traits and germination in the Cactaceae family: A review across Americas

“…Few studies have used thermal shock but without obtaining good results with this type of treatment (Sánchez-Venegas 1997, Rosas-López & Collazo-Ortega2004, Carbajal et al 2010, Villanueva et al 2016, Podda et al 2017, Gonzalez-Cortés et al 2018. Other studies have used fungal inoculation in some species of Opuntia (Delgado- Sánchez et al 2010Sánchez et al , 2013 or hydration/dehydration cycles (Dubrovsky 1996, Santini & Martorell 2013, Contreras-Quiroz et al 2016a, 2016b with good results. Research in the last decade that has addressed treatments to break dormancy in cactus seeds are however, not common (Rojas-Aréchiga et al 2011, Amador-Alférez et al 2013, Delgado-Sánchez et al 2010, Podda et al 2017, Gonzalez-Cortés et al 2018.…”

“…Two pioneering studies of Dubrovsky (1996Dubrovsky ( , 1998 demonstrated the utility of the hydration-dehydration cycles in increasing the speed and final percentage of germination in four cactus species. However, still there are a few cactus studies (Table 1) that address these treatments as germination promoters (Sánchez-Soto et al 2005, Rito et al 2009, Santini & Martorell 2013, López-Urrutia et al 2014, Contreras-Quiroz et al 2016a, 2016b, Santini et al 2017, although hydration-dehydration cycles have been and are widely used in innumerable species worldwide . The evaluation of this type of pre-germinative treatment in cactus seeds should be tested more in the future, because the seeds are subject to hydrationdehydration cycles in nature, which can influence not only germination but also aspects related to conditional or cyclical dormancy, seed longevity and seedling survival, among others .…”

Physiological ecology of Mexican CAM plants: history, progress, and opportunities

“…Hydration memory. Desert plants have developed strategies to germinate even in places where available moisture is sporadic (Dubrovsky 1996, Contreras-Quiroz et al 2016a. Seeds of some cactus species have desiccation tolerance of imbibed seeds or "hydration memory," a seed ability to retain some of the physiological changes, like the differential expression of proteins (López-Urrutia et al 2014), induced by hydration-dehydration cycles (Dubrovsky 1996).…”

“…In addition, higher germination percentage with hydration-dehydration cycles have been found for Ferocactus pilosus and Echinocactus platyacanthus; however, Yucca filifera seeds germinated more with the control than with the hydration-dehydration treatments. Thus, "hydration memory" is not a trait present in all CAM species (Contreras-Quiroz et al 2016a) nor exclusive to CAM species, e.g., several non-CAM species of the Mediterranean region show seed hydration memory (Copete et al 2021).…”

Mamíferos De Médio E Grande Porte Em Um Fragmento De Floresta Estacional Semidecidual Em Minas Gerais

“…As chuvas variam de 240 a 900 mm por ano (SAMPAIO, 1995;PENNINGTON et al, 2000 De acordo com Dubrovsky (1996;1998), essa condição natural de hidratação descontínua proporciona às sementes um elevado índice de sobrevivência durante a dessecação, demonstrando que essas sementes podem apresentar uma "memória hídrica". Tal fato está relacionado ao processo de embebição, no qual, algumas sementes são capazes de preservar as características resultantes da hidratação prévia e ativar genes específicos da planta relacionados à tolerância aos estresses ambientais (BRUCE et al, 2007;CONTRERAS-QUIROZ et al, 2016;MEIADO, 2013 , 1997;QUEZADA et al, 1999;MOURA et al, 2016) , um ciclo (B) dois ciclos (C) e três ciclos (D) de hidratação e desidratação (HD) sob diferentes intervalos de suspensão de rega (Controle, E7 e E14). Plantas regadas diariamente (E), plantas regadas a cada sete dias (F) e plantas regadas a cada 14 dias (G) cujas sementes que passaram por 0, 1, 2 e 3 ciclos de HD.…”