Cellular Biochemical Changes in Selaginella tamariscina (Beauv.) Spring and Sellaginella plana (Desv. ex Poir.) Heiron. as Induced by Desiccation

Abstract

The biochemical changes in two Selaginella species namely, S. tamariscina (Beauv.) Spring and S. plana (Desv. ex Poir.) Heiron., as induced by desiccation and subsequent rehydration were explored. Plants were allowed to dehydrate naturally by withholding irrigation until shoot’s relative water content (RWC) reached <10%. After which, dehydrated plants were watered until fully rehydrated states were obtained which was about 90% RWC or more. Desiccation-tolerance characteristics were observed in S. tamariscina while desiccation-sensitivity features were seen in S. plana. Membrane integrity was maintained in S. tamariscina but not in S. plana as evidenced in the relative electrolyte leakage measurements during desiccation phase and the subsequent rehydration stage. Pigment analyses revealed conservation of some chlorophylls and carotenoids during desiccation and reaching control levels following rehydration in S. tamariscina. Very low pigment contents were found in S. plana during desiccation phase and the pigments were not recovered during rehydration attempt. Meanwhile, compatible solute determination showed rise in total sugar and proline contents of desiccated S. tamariscina only, indicating presence of biochemical protection machineries in this species and absence of such in S. plana during dehydrating conditions. These data indicate that one key element for desiccation-tolerance in lower vascular plants is the ability to protect tissues from severe damages caused by intense desiccation.

Perubahan biokimia dalam dua spesies Selaginella iaitu S. tamariscina (Beauv.) Spring dan S. plana (Desv. ex Poir.) Heiron., yang dicetuskan oleh pengeringan dan diikuti oleh rehidrasi telah dikaji. Tumbuhan telah dibenarkan untuk dehidrat secara semula jadi dengan menyekat pengairan sehingga kandungan air relatif (RWC) pucuk bernilai <10%. Kemudiannya, tumbuhan yang dehidrat disiram air sehingga mencapai keadaan rehidrasi sepenuhnya iaitu RWC 90% ataupun lebih. Sifat-sifat menahan pengeringan telah diperhatikan dalam S. tamariscina manakala sifat sensitif terhadap pengeringan dilihat pada S. plana. Integriti membran dikekalkan dalam S. tamariscina tetapi bukan dalam S. plana seperti yang dilihat dalam ukuran kebocoran elektrolit relatif semasa fasa pengeringan dan seterusnya semasa fasa rehidrasi. Analisa pigmen telah menunjukkan konservasi beberapa klorofil dan karotenoid semasa pengeringan dan mencapai tahap kawalan yang mengikuti proses rehidrasi dalam S. tamariscina. Kandungan pigmen yang sangat rendah telah dijumpai dalam S. plana semasa fasa pengeringan dan pigmen tersebut tidak dipulih semula semasa rehidrasi. Penentuan zat terlarut yang serasi menunjukkan kenaikan dalam kandungan gula dan proline dalam S. tamariscina kering sahaja, yang menunjukkan kewujudan jentera-jentera perlindungan biokimia dalam spesies ini dan ketidakhadirannya dalam S. plana semasa keadaan dehidrat. Data-data ini menunjukkan satu elemen penting untuk toleransi terhadap pengeringan dalam tumbuhan vaskular rendah ialah kebolehan melindungi tisu-tisu daripada kemusnahan serius akibat pengeringan yang teruk.