Effect of Desiccation and Scarification on the Permeability and Structure of the Seed Coat of Cuscuta campestris

Abstract

Changes occurring within the seed coat of Cuscuta campestris Yunkr. during desiccation were correlated with a decrease in germinability. Germination initially increased as the embryo matured, but then decreased as the testa dried. Completion of macrosclereid development signaled the onset of dormancy. Mechanical scarification with sandpaper or immersion in concentrated H2SO4 broke dormancy. The impermeable layer is a region above the light line and at the junction of the hypodermis and the palisade cell layers. This region appeared to be deposited during desiccation of the hypodermis. Overwintering or a period of cold storage also broke dormancy. The change in permeability was found throughout the testa rather than in a specific area.

Temperature effects on Cuscuta campestris Yunk. seed germination

“…At all other test temperatures, germination ranged from 13.75 to 96.88% (Figures 1-7) and the highest germination rate was recorded at 30°C (T 1 : 20.63%, T 2 : 38.75%, T 3 : 96.88%). Similar results had been reported by Hutchison and Ashton (1979) under laboratory conditions with C. campestris seeds, whose dormancy was broken by mechanical scarification using abrasive paper dipped in concentrated sulphuric acid. The recorded germination was negligible at 10°C and the highest at 30°C.…”

“…Dormancy of C. campestris occurs owing to its hard seed coat (Lyshede, 1992). The percentage of hard seeds at dispersal varies among C. campestris (Hutchison and Ashton, 1979) and C. chinensis plants (Marambe et al, 2002). Dormancy can be broken by the activity of soil microorganisms or by tillage, causing scarification of seed coat (Haidar et al, 1999).…”

Seed structure and germination in Cuscuta pedicellata with some notes on C. campestris

“…No functional explanation was offered. Ashton & Santana (1976) and Hutchinson & Ashton (1979) observed bulging in C . campestris seeds during chemical scarification with H2S04, but they apparently assumed this to be a stage in the degradation process of the epidermal cells due to the acid.…”

“…In C. pedireftatu the rapid swelling of the epidermal cells will ensure a better contact with the substrate and presumably a more efficient water uptake by the aid of the pectinaceous content in the wall. Furthermore, the ability of the whole surface to swell suggests that water uptake can take place through any part of the seed surface as was demonstrated for C. campestris by Hutchison & Ashton (1979). The slit-like pits in the cell wall may ensure that all cells become water-filled, even when only some cells are in direct contact with water.…”

The biology of Canadian weeds. 133. Cuscuta campestris Yuncker, C. gronovii Willd. ex Schult., C. umbrosa Beyr. ex Hook., C. epithymum (L.) L. and C. epilinum Weihe.

“…from temperate regions undergo a cyclical dormancy/non-dormancy pattern in the soil similarly to other plants (Baskin and Baskin 1998). Breaking down dormancy requires mechanical or chemical scarification (Gaertner 1950;Tingey and Allred 1961;Hutchinson and Ashton 1979;Lyshede 1984). Treatments of C. campestris seeds with sulfuric acid for 30-80 min, or the abrasion between layers of fine sandpaper resulted in over 75% germination (Gaertner 1950;Ashton and Santana 1976;Kroschel 2001).…”