A Comparative Account of the Pith Flecks ofAnnona squamosaLinn. andWalsura piscidiaRoxb.

Abstract

The pith flecks of Annona squamosa and Walsura piscidia wcre comparcd with rcfcrcnce to thcir structural organization and to thcir cffcct on the adjacent wood. In both cases, thc flccks wcrc causcd by thc mining activity of cambium mincrs of the insect group Agromyzidae. In both, flccks wcrc composcd of parenchymatous clcments dcrivcd partly from ray and partly from axial parcnchyma adjoining thc minc. Thcre were more flecks per unit arca of wood in Annona than in Walsura, A fcw diffcrenccs wcre observed bctwccn the flecks of the two plants and thcsc includc (1) prcscncc of some unfillcd or partially filled mined tunncls in Annona, (2) abscnce of starch grains in the cclls of fleck in Walsura, (3) thinncr bordering nccrotic laycr around the fleck in Walsura, and (4) abscnce of pcctin in thc fleck ccll wall in Walsura. The wood adjacent to pith flccks in Annona showcd an incrcasc in thc hcight and width of rays. These differenccs, however, were not noticcd in Walsura, probably bccausc of thc limitcd numbcr of flccks per unit arca of wood.

Anatomy and Ultrastructure of Pith Fleck-Like Tissues in Some Rosaceae Tree Species

“…The pith fleck has been defined as an irregular strand of abnormal parenchymatous tissues embedded in the xylem, appearing as a streak on a longitudinal section (I AW A 1964). In comparing the anatomy of pith flecks described in previous studies (Bhat 1980;Gregory & Wallner 1979;Grossenbacher 1910;Kalavathi & Krishnamurthy 1989;Krishnamurthy et al 1986) to the unusual xylem tissues described herein, it is easy to establish similarities. In transverse sections, PFL Ts and pith necks have about the same size and appearance, and are constituted of comparable hypertrophied parenchyma cells; they extend also continuously for many cm longitudinally.…”

“…Previous studies on pith necks have indicated the presence of bands of darkly stained material usually bordering the parenchyma cells that were apparently composed of necrotic cells (Gregory & Wallner 1979;Grossenbacher 1910;Kalavathi & Krishnamurthy 1989;Krishnamurthy et al 1986) and also of insect frass (Grossenbacher 1910). To our knowledge, this is the first time that TEM examination is provided about such tissues and our observations clearly showed that these bands were composed of collapsed cells.…”