Science Links Japan | Physiological Role of Plant Cystolith-Its Possible Role in Suppressing the pH Increase Coupled with Nitrate Reduction in the Leaves.

Physiological Role of Plant Cystolith-Its Possible Role in Suppressing the pH Increase Coupled with Nitrate Reduction in the Leaves.

Accession number;03A0714649

Title;Physiological Role of Plant Cystolith-Its Possible Role in Suppressing the pH Increase Coupled with Nitrate Reduction in the Leaves.

Author; KAI NAOKAZU (Tokyo Gakugei Univ.) OKAZAKI MEGUMI (Tokyo Gakugei Univ.)

Journal Title;Bulletin of Tokyo Gakugei University. Section 4. Mathematics and Natural Sciences

Journal Code:G0326A

ISSN:0371-6813

VOL.55;NO.;PAGE.201-212(2003)

Figure&Table&Reference;FIG.11, TBL.1, REF.21

Pub. Country;Japan

Language;Japanese

Abstract;The plant cystoliths, small CaCO3 bodies, were formed in he leaves of certain species among dicotyledon families such as Urticaceae, Moraceae, Ulmaceae, Cucurbitaceae and Acanthacae. Their number (particles/cm2) varies from 1,000 to 4,000, depending on species. However, the physiological role of cystolith formation was not clear, although many hypotheses have been proposed. Raven and Smith (1976) proposed that CaCO3 deposition in cystolith is coupled with nitrate assimilation in the leaves. The CaCO3 formation could neutralized OH- produced from ammonia, which is the product of nitrate assimilation (NO3-.RAR.NH4OH), i.e. a possible function of cystolith as a "pH stat". In this study we compared the activity of nitrate reductase (nmol NO2- formed/.MU.g protein/min) in the leaves of cystolith-forming and non-forming speies among the same family. The following results were obtained: (1) It is likely that the cystolith-forming species such as Celtis sinensis (Ulmaceae) and Momordica charantia (Cucurbitaceae) had higher enzyme activity than non-forming species such as Zelkova serrata (Ulmaceae) and Cucumis sativus (Cucurbitaceae), respectively. (2) Young leaves of cystolith-forming species such as Ficus retusa (Moraceae) and Beloperone guttata (Acantaceae) had higher activity than their old leaves and (3) their young leaves had smaller cystoliths than their old leaves. These results may support the "pH stat" hypothesis proposed by Raven and Smith. (author abst.)

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