Effect of temperature, light and salinity on seed germination and radicle growth of the geographically widespread halophyte shrub Halocnemum strobilaceum.

BACKGROUND AND AIMS: The small leafy succulent shrub Halocnemum strobilaceum occurs in saline habitats from northern Africa and Mediterranean Europe to western Asia, and it is a dominant species in salt deserts such as those of north-west China. The effects of temperature, light/darkness and NaCl salinity were tested on seed germination, and the effects of salinity were tested on seed germination recovery, radicle growth and radicle elongation recovery, using seeds from north-west China; the results were compared with those previously reported on this species from 'salt steppes' in the Mediterranean region of Spain. METHODS: Seed germination was tested over a range of temperatures in light and in darkness and over a range of salinities at 25 degrees C in the light. Seeds that did not germinate in the NaCl solutions were tested for germination in deionized water. Seeds from which radicles had barely emerged in deionized water were transferred to NaCl solutions for 10 d and then back to deionized water for 10 d to test for radicle growth and recovery. KEY RESULTS: Seeds germinated to higher percentages in light than in darkness and at high than at low temperatures. Germination percentages decreased with an increase in salinity from 0.1 to 0.75 M NaCl. Seeds that did not germinate in NaCl solutions did so after transfer to deionized water. Radicle elongation was increased by low salinity, and then it decreased with an increase in salinity, being completely inhibited by > or = 2.0 M NaCl. Elongation of radicles from salt solutions < 3.0 M resumed after seedlings were transferred to deionized water. CONCLUSIONS: The seed and early seedling growth stages of the life cycle of H. strobilaceum are very salt tolerant, and their physiological responses differ somewhat between the Mediterranean 'salt steppe' of Spain and the inland cold salt desert of north-west China.

[Effects of sand burying on caryopsis germination and seedling growth of Bromus inermis Leyss].

This paper studied the effects of different depth sand burying on the caryopsis germination, seedling emergence and growth of Bromus inermis Leyss., a perennial gramineous grass dominated on Othidag sandy land. The results showed that the maximum burying depth for B. inermis caryopsis germination and seedling emergence was 12 cm and 8 cm, respectively. Below the thresholds, the percentages of caryopsis germination and seedling emergence decreased with increasing depth of sand burying. All the 1- and 2-week-old seedlings of B. inermis could survive when the sand burying depth was up to 33% of their height, and their biomass was no less than the unburied seedlings. When the burying depth increased to 66% of their height, 70% of 1-week-old seedlings and 25% of 2-week-old seedlings could survive, but their growth was impaired. No seedlings could survive when they were wholly buried in sand. When buried by sand, the seedlings allocated more biomass for the development of their aboveground part, which might be an important adaptation strategy of B. inermis to sand burying.