Growth Response of Orchardgrass (Dactylis glomerata L.) to Different Light and Temperature Environments. II. Leaf Age and Photosynthetic Activity¹

Abstract

The variation in rate of apparent photosynthesis (PR) with leaf age in three populations of orchardgrass, grown in two different temperature environments, was investigated using a Warburg manometric technique. Fully expanded leaves maintained a high PR for 15 to 20 days but the rate rapidly declined thereafter. PR (oxygen evolution) per unit leaf area closely paralleled the synthesis and degradation of the chlorophyll pigments; PR per unit chlorophyll changed very little throughout the life of the leaf. These results were confirmed by the pattern of assimilation of C14O2 by leaves of different ages. The Portuguese ecotype had a significantly higher photosynthetic rate at 21 C than the cultivars ‘S.143’ and ‘Boone’ in both growth environments. Plants grown at 21 C day/13 C night temperatures had a significantly higher rate at 21 C than plants grown at 29 day/21 night temperatures, but when measured at 29 C plants grown in the higher temperature regime had a significantly higher rate of PR. The relative pattern of change of PR with leaf age was unaffected by the temperature at which the plants were grown.

Modelling net photosynthetic rate of field‐grown cocksfoot leaves to account for regrowth duration

“…2D). Treharne et al (1968) also found that leaf chlorophyll content in cocksfoot decreases with age. Treharne & Eagles (1970) reported a fall of 60% in RuBisCO activity of the youngest fully expanded cocksfoot leaves after 30 days' full expansion at 25°C.…”

“…For grasses, the negative effect of leaf age on leaf photosynthesis in different positions on one tiller, and during ageing of leaves in a particular position on the tiller, has previously been reported (e.g., Jewiss & Woledge 1967;Treharne et al 1968;Treharne & Eagles 1970;Woledge 1972;Robson & Parsons 1978). …”

“…46 For grasses, the effect of leaf age on leaf photosynthesis (i) in different positions on one tiller and (ii) during ageing of leaves in a particular position on a tiller, has been quantified (Treharne et al 1968;Treharne & Eagles 1970;Woledge 1972;Robson & Parsons 1978). However, the effect of regrowth duration on the photosynthetic capacity of leaves that are of the same physiological age, such as the first fully expanded leaf, has received less attention (Woledge & Leafe 1976;Woledge & Pearse 1985).…”

APPARENT PHOTOSYNTHESIS AND LEAF CHARACTERS IN RELATION TO LEAF POSITION AND AGE, AMONG CONTRASTING LOLIUM GENOTYPES

“…However, a slow, steady decline of photosynthesis per unit chlorophyll led Treharne et al (1968) to suggest that the peak of photosynthetic efficiency was at, or just before, the period of most rapid leaf expansion, and that there was a gradual deterioration with leaf age. From the present results, it appears that the differences in chlorophyll between successive leaves observed by Treharne et al (1968) may have reflected a difference in mesophyll cell size (Table 3). The present results also indicate that lower leaves, which are more efficient in the use of CO2 than the upper leaves, might often be shaded by less efficient leaves while still capable of maximum response to light.…”

Une régie de trois coupes chez le dactyle (Dactylis glomerata L.) en régions agricoles du Moyen-Nord de l'Est du Canada

“…Après l'expansion totale de la feuille, un haut niveau de photosynthèse est maintenu pour 15 à 20 jours. Par la suite, le taux de photosynthèse diminue rapidement (Treharne et al 1968). Jung et Baker (1985) ont mentionné qu'il y avait peu d'avantage au point de vue production à espacer les coupes de plus de 35 à 42 jours.…”