[Rapid propagation system for tissure culture of Smilax glabra]

OBJECTIVE

Establishing the rapid propagation for plant tissue culture of Smilax glabra in order to rationally protect and utilize the resource.

METHODS

The seed, shoot, leaf and rhizome of Similax glabra were cultured as explants. Different media and plant growth regulators at different concerntration were used.

RESULTS

The best medium for bud induction was MS + 6-BA 2.0 mg/L + NAA 0.05 mg/L; The optimal medium for proliferation culture was MS +6-BA 2.0 mg/L + NAA 0.5 mg/L; The optimal medium for rooting was H + IBA 0.5 mg/L + NAA 0.5 mg/L; The optimal stroma for seedlings was 50% peat + 50% river sand.

CONCLUSION

Different explants except leaf can be induced for tissue culture and rhizome has the optimal bud induction rate. An effective approach for rapid propagation has been provided,which can promote the artificial cultivation of Smilax glabra.

Developmental origins of the conjoined twin mature embryo sacs in Smilax davidiana, with special notes on the formation of their embryos and endosperms

PREMISE OF THE STUDY

Smilax davidiana, a perennial deciduous vine in Smilacaceae, is widely distributed in East and South China. A recent investigation revealed the existence of twin embryo sacs in this species. This study describes their mature structure, analyzes their developmental origins, and discusses the formation of their embryos and endosperms.

METHODS

Conventional paraffin section, light microscopy, and various staining techniques were used to document the course of megasporogenesis and mature embryo sac structure in pistillate flowers.

KEY RESULTS

Two chalazal megaspores of the tetrad became functional, giving rise to twin embryo sacs. Two mature embryo sacs of the same size (equal-conjoined twins); a dominant mature embryo sac and a subordinate one (unequal-conjoined twins); or very rarely, fully fused twin mature embryo sacs sharing a common chalazal domain are formed.

CONCLUSION

A single embryo occurring in conjoined twins is the outcome of two eggs competing for sperm rather than a result of contention of two pre-embryos (or young embryos) for nutrition. Conjoined twin embryo sacs could provide a new pathway to the formation of pentaploid endosperms.

Tracheid analysis and modeling of the minor veins of the coleus and smilax leaves

Tracheid analysis was carried out on the veinlets and minor veins of the coleus (Solenostemon scutellarioides [L.] Codd) leaf. Third- to fifth-order, or minor, veins average 3.4 tracheids in tandem and they bipartition islets when these enclosed islets reach a critical size; both these features of vein length and islet size contribute to a self-similar process of vein pattern generation. An areole was calculated to be initially comprised of about ten cells making the patterning event for vein formation requiring only a few cells. An algorithmic model developed here for minor vein formation includes five production rules, and this computer model explains the 3-4 tracheids per minor vein, presence of isolated tracheids, the structure of veinlets, and the elaborate branching patterns of veinlets in coleus and other plants.

[Rapid propagation of Smilax glabra in vitro]

In vitro propagation of Smilax glabra Roxb. was studied. The results indicated that sterilized explants cultured on MS + 6-BA 1.0 mg/L + NAA 0.1 mg/L could lead to budding fastly, the medium MS + 6-BA 1.0 mg/L + NAA 0.1 mg/L + 15% CM suitable for the proliferation, 3/2MS + 6-BA 0.05 mg/L + 4% Sugar suitable for buds strong. Treatment on the medium H (modified) + NAA 0.5 mg/L was best for rooting. The survival rate of the test-tube plantlets was 95% in transplanting on media contained turf-sand (1:1).

Water sources and water-use efficiency in mediterranean coastal dune vegetation

In coastal environments plants have to cope with various water sources: rainwater, water table, seawater, and mixtures. These are usually characterized by different isotopic signatures ( (18)O/ (16)O and D/H ratios). Xylem water reflects the isotopic compositions of the water sources. Additionally, water-use efficiency (WUE) can be assessed with carbon isotope discrimination (Delta) analyses. Gas exchange, Delta of leaf dry matter, and isotopic composition (delta (18)O) of xylem water were measured from June to August 2001 in herbaceous perennials of mobile dunes (Ammophila littoralis, Elymus farctus) and sclerophyllous shrubs and climbers (Arbutus unedo, Pistacia lentiscus, Phillyrea angustifolia, Qercus ilex, Juniperus oxycedrus, Smilax aspera) of consolidated dunes. Assimilation rates were rather low and did not show clear seasonal patterns, possibly due to limited precipitation and generally low values of stomatal conductance. The lowest values were shown in S. aspera. Different physiological patterns were found, on the basis of delta (18)O and Delta analyses. Values of delta (18)O of xylem water of phanerophytes were remarkably constant and matched those of the water table, indicating dependence on a reliable water source; values of Delta were relatively high, indicating low intrinsic WUE, with the exception of J. oxycedrus. Surprisingly, very high delta (18)O values were found for the xylem water from S. aspera in August. This suggests retrodiffusion of leaf water to xylem sap in the stem or direct uptake of water by leaves or stems, owing to dew or fog occurrence. Low Delta values indicated high WUE in S. aspera. Contrasting strategies were shown by the species of mobile dunes: E. farctus relied on superficial water and exhibited low WUE, accordingly to its therophyte-like vegetative cycle; on the contrary, A. littoralis used deeper water sources, showing higher WUE in relation to its long-lasting vegetative habit.