Grass leaf blade development: Modification of the source

Abstract

. Grass leaf blade development: Modification of the source. Can. J. Plant Sci. 79: 361-363. Developing leaf blades of tall fescue (Festuca arundinacea Schreb.) were subjected to three treatments that modify their source capacity: (1) emerged tips cut daily, (2) grown in darkness or (3) grown at the CO 2 compensation point. Treated and control leaves developed similarly but treated leaves senesced rapidly at the leaf tip. Reduction of carbon availability in developing tall fescue leaf blades seems not to penalize normal blade development but does reduce the lifespan of mature leaves.Key words: Source, leaf development, tall fescue Brégard, A. et Allard, G. 1999. Développement de limbes de graminées: modification de la source. Can. J. Plant Sci. 79: 361-363. Des limbes en développement de fétuque élevée (Festuca arundinacea Schreb.) ont été soumis à trois traitements afin de modifier leur capacité source: (1) extrémités émergées des feuilles coupées quotidiennement, (2) maintenues à l'obscurité ou (3) développées au point de compensation en CO 2 . Les développements des feuilles traitées et témoins étaient similaires mais l'extrémité des feuilles traitées se nécrosaient rapidement. La disponibilité réduite en carbone dans les limbes n'affecte pas leur développement mais réduit la durée de vie des feuilles matures. Mots clés: Source, développement foliaire, fétuque élevéeIn developing grass leaves, the tip of the blade is structurally mature and photosynthetically active by the time it emerges from the whorl formed by the sheath of older leaves. Hence photoassimilates produced by the leaf tip could be exported towards the growing leaf base which, in turn, also imports photoassimilates from mature leaves (Anderson and Dale 1983). Anderson and Dale (1983) determined that by the time a barley leaf is half expanded it can provide about half of its own photoassimilate requirement. Similarly, Ryle and Powell (1972) determined that in Lolium leaves, 60 to 80% of photoassimilates produced in the emerged leaf tip are used in the basal growing zone when the blade is one-third to one-half expanded.The balance between imported and produced photoassimilates in a developing leaf blade is continuously modified by the increasing photosynthetic capacity of the expanding leaf tip. Eventually, a positive carbon balance is reached, i.e. more carbon is fixed by the leaf than is required for its growth and respiration. On average, when a leaf from a dicotyledonous species reaches 50% of its full development, the pattern of importation changes and the sink-to-source transition occurs (Turgeon 1989). In tall fescue (Festuca arundinacea Schreb.) leaf blades, a monocotyledon, the sink-to-source transition occurs when the blade reaches 80% of its final length (Brégard and Allard 1999); this also corresponds to the onset of sheath elongation and the development of the next leaf.Leaf blade elongation and development could therefore be related to the carbon autotrophy of the blade and as such, the period of the sink-to-source transition could b...

Leaf transition from heterotrophy to autotrophy is recorded in the intraleaf C, H and O isotope patterns of leaf organic matter

“…Deposition of the primary cell wall (and veins of various orders) occurs when the cell is still expanding while deposition of the secondary cell wall (and veins of various orders) occurs after cell expansion has stopped 35 . Thus, it can be inferred that the secondary cell wall probably contributes to the cell wall thickness, and hence to leaf width increase following cessation of longitudinal growth as seen in the C 3 monocotyledonous grass Festuca arundianacea Shreb 36,37 . As Liu et al 38 showed that α‐cellulose (a major component of cell wall) deposition stopped at (or shortly after) full leaf expansion in a perennial C 4 monocotyledonous grass Cleistogenes squarrosa , it can also be inferred that the hemicellulose is probably the dominant component of the secondary wall.…”