Alleviation of salinity stress and the response to temperature in two seed morphs of Halopyrum mucronatum (Poaceae)

Abstract

Halopyrum mucronatum (L.) Stapf. is a coastal dune grass that produces seeds twice during each growing season. Seeds produced during May (summer seed) were black and heavier (2.8 ± 0.09 mg) than brown seeds (2.1 ± 0.04 mg; winter seed) that were produced in November. There was greater than 95% germination in both seed morphs in the non-saline controls at all temperature regimes, but germination was inhibited more by low than high temperatures in the salinity treatments. Summer seeds were more tolerant of salinity than the winter seeds. Highest germination was obtained in all salinity treatments at a 20/30°C (12-h night/12-h day) temperature regime for the winter seeds and at 25/35°C for the summer seeds. Gibberellic acid, thiourea and nitrate partially alleviated the effects of salinity in summer seeds and gibberellic acid, kinetin and betaine were able to alleviate the inhibitory effects of salinity on the germination of winter seeds. The seeds of Halopyrum mucronatum exhibited seed dimorphism and a difference in physiological response in the two seed morphs, which could provide them with multiple opportunities to germinate and establish in the hot, dry, saline and unpredictable maritime coastal-dune environment along the Arabian Sea coast of Karachi, Pakistan. G e r mi n a t i o n o f Ha l o p y r u m m u c r o n a t u m M . A . K h a n a n d I . A . U n g a r B T 0 1 0 1 4

Effects of salinity and desalination on seed germination of six annual weed species

“…acuminatum. Similar trends have been found in many halophytes Ungar 1996a, 1996b;Khan et al 1998;Katembe et al 1998;Ishikawa and Kachi 2000;Khan and Ungar 2001;Khan et al 2003). Moderate (50-200 mM) but higher saline concentration (300 mM) did not significantly inhibit seed germination of E.pilosa, whereas lower salinity (50 mM) significantly increased seed germination percentage of Ch.glaucum.…”

The effect of plant growth regulators, nitric oxide, nitrate, nitrite and light on the germination of dimorphic seeds of Suaeda salsa under saline conditions

“…Khan and Ungar (2002) reported that nitrate and thiourea promoted the germination of Zygophyllum simplex seeds at the lowest (25 mM NaCl) salinity but did not promote germination at higher (125 mM NaCl) salinities. Seed germination of Allenrolfea occidentalis and Halopyrum mucronatum, however, is promoted by thiourea in NaCl treatments (Gul and Weber 1998;Khan and Ungar 2001c). Some nitrogenous compounds such as SNP, nitrate, nitrite, and thiourea are known to stimulate the germination of seeds (Esashi et al 1979;Aldosaro et al 1981;Yoshiyama et al 1996;Beligni and Lamattina 2000;Batak et al 2002).…”

Effects of Dormancy Regulating Chemicals on Innate and Salinity Induced Dormancy in the Invasive Prosopis juliflora (Sw.) DC. Shrub

“…Thiourea significantly alleviated the salinity-induced dormancy in winter seeds of Halopyrum mucronatum (Khan and Ungar 2001a), in Sporobolus arabicus (Khan and Ungar 2001c), but only partially alleviated it in Triglochin maritima (Khan and Ungar 2001b). Nitrogenous compounds are known to promote germination by acidification and softening of cell walls or by activating the pentose phosphate pathway (Esashi et al 1979).…”

“…Kinetin and GA 3 partially alleviated the germination inhibition at higher salinity (600 mM NaCl) in P. juliflora. Both these compounds are known to alleviate the salinity-induced germination inhibition in Brassica campestris (Ozturk et al 1993), Zygophyllum simplex (Khan and Ungar 1997), Halopyrum mucronatum (Khan and Ungar 2001a), Atriplex halimus (Debez et al 2001), Salicornia rubra . There was a partial alleviation in salinity induced dormancy by kinetin in Triglochin maritima (Khan and Ungar 2001b) and by GA 3 in Salicornia pacifica (Khan and Weber 1986).…”