This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (140) Citing Articles via Google Scholar Google Scholar Articles by Robertson, D. Articles by Laetsch, W. M. Search for Related Content PubMed PubMed Citation Articles by Robertson, D. Articles by Laetsch, W. M. Agricola Articles by Robertson, D. Articles by Laetsch, W. M.

Articles

Structure and Function of Developing Barley Plastids ¹

^a Department of Botany, University of California, Berkeley, California 94720

Five different regions of the first foliage leaf of etiolated barley seedlings were studied with respect to leaf growth, plastid growth and replication, differentiation of etioplasts, and conversion of etioplasts into chloroplasts upon illumination. Ultrastructural changes of the plastids were correlated with chlorophyll synthesis and development of photosynthetic activity as measured by ¹⁴CO₂ incorporation and O₂ evolution. The first foliage leaf has greater linear growth over a longer period of time in the dark than in the light. Only the bottom two regions (4 and 5) are still growing in the 5-day etiolated leaf. Region 4 grows by cell elongation, and region 5 grows by both cell division and elongation. Plastids in all five regions of the leaf are capable of enlarging when exposed to light. This is true both for the intact plant and for excised sections. Plastid replication occurs predominantly in the younger regions of the leaf (regions 3, 4, and 5). The amount of chlorophyll synthesized by different regions in the intact plant is significantly higher (3-40 times) than that made by excised sections. Ultrastructural changes occurring in each region when excised sections are illuminated were classified into five stages involving increased membrane synthesis and appression into grana, and these changes were correlated with the first appearance of photosynthetic activity. The earliest detectable photosynthetic activity occurs in region 1 after 2 hours of illumination when chloroplasts show only a few overlaps in the thylakoids. Plastids in younger regions of the leaf require up to 24 hours of light to form grana and develop photosynthetic activity. Plastids in each region of the leaf are in different stages of development when photosynthesis is initiated, indicating that development of photosynthetic activity is not strictly correlated with a certain stage of plastid development. Membrane appression is not indicative of photosynthetic activity since overlaps are formed in the dark, but it was always present when photosynthetic activity was detectable. Likewise, there does not appear to be any strict correlation between the presence of chlorophyll and membrane appression. These results show that the particular structural and functional correlations that can be made depend to a large degree on age of the tissue.

¹ Supported by a National Science Foundation Predoctoral Fellowship to Diane Robertson and by National Science Foundation Grant GB-12964.

This article has been cited by other articles:

				M. A. Ayliffe, A. Agostino, B. C. Clarke, R. Furbank, S. von Caemmerer, and A. J. Pryor Suppression of the Barley uroporphyrinogen III synthase Gene by a Ds Activation Tagging Element Generates Developmental Photosensitivity PLANT CELL, March 1, 2009; 21(3): 814 - 831. [Abstract] [Full Text] [PDF]

				S. Woitsch and S. Romer Expression of Xanthophyll Biosynthetic Genes during Light-Dependent Chloroplast Differentiation Plant Physiology, July 1, 2003; 132(3): 1508 - 1517. [Abstract] [Full Text] [PDF]

				L. A. Eichacker, M. Helfrich, W. Rudiger, and B. Muller Stabilization of Chlorophyll a-binding Apoproteins P700, CP47, CP43, D2, and D1 by Chlorophyll a or Zn-pheophytin a J. Biol. Chem., December 13, 1996; 271(50): 32174 - 32179. [Abstract] [Full Text] [PDF]