Ultrastructural changes in chloroplasts of mesophyll cells of chlorotic and prematurely yellowed leaves of Betula pendula Rothr

Krystyna Przybył,Krystyna Idzikowska

doi:10.5586/asbp.2003.037

Abstract

The ultrastructure of chloroplasts was studied in mesophyll cells of the leaves of silver birch (<em>Betula pendula</em>) showing interveinal chlorosis or premature yellowing, in comparison with leaves without symptoms or exhibiting symptoms of natural senescence. The leaves were collected between May 26 to June 7 and additionally in the September 10-12 from the upper part of the crown, from increments of the past four years. No major difference in ultrastructure of chloroplasts was found between spongy and palisade mesophyll cells. The following senescencerelated changes were observed in chloroplasts of prematurely yellowed leaves and showing inteveinal chlorosis: reduced chloroplast size, degeneration of the membrane systems of thylakoids and increased electron density of plastoglobuli. The most electron dark globules (lipid droplets) were found together with starch grains in cells of spongy mesophyll of leaves showing interveinal chlorosis. Abnormal, spherical and rounded chloroplasts with electron-dark inside of thylakoids or the electron-dark stroma between thylakoids were found only in yellowed and chlorotic leaves in spring.

Highlights

IntroductionDecline of birch stands (Betula pendula) has been recorded in Poland, but its intensity varied from one birch stand to the next
For ten years, decline of birch stands (Betula pendula) has been recorded in Poland, but its intensity varied from one birch stand to the
No apparent cytological differences were noted between the palisade and spongy mesophylls

Summary

Introduction

Decline of birch stands (Betula pendula) has been recorded in Poland, but its intensity varied from one birch stand to the next. The most noticeable macroscopic symptoms occurring in above-ground organs are as follows: crown thinning due to dieback of fine twigs and branches in the tree-top, wounds and slime flux on the trunk, brown bark and sapwood inside branches and trunk, showing sometimes a water-saturated appearance (Przyby et al 1998; Przyby and3obiñska-Podejma 2000; Przyby3 2001). Leaves of the declining trees usually turn yellow prematurely. Irrespective of this symptoms, chlorosis between veins of leaves is observed in majority of trees. It is suspected that the symptoms in birch leaves could be related to the prolonged periods of drought recorded in Poland in the past few years. It seems plausible that the K, Mg, and N deficiency is involved in accelerated yellowing (Przyby and Mañka 2000)

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