Seasonal Changes in the Photosynthetic Rate in Apple Trees

Abstract

Seasonal changes in photosynthesis of apple trees (Malus domestica Borkh.) were monitored to examine the effect of source-sink interactions on photosynthesis and photorespiration. Elevated photosynthetic rates were observed during two periods of the growing season and correlated with the fruiting process. The first period of increased photosynthetic rates was during the bloom period, when spur leaves on flowering shoots exhibited up to 25% higher photosynthetic rates than vegetative spur leaves on a leaf area basis. CO2 assimilation rates were also higher in fruiting trees than nonfruiting trees during the period of rapid fruit growth from July to September. Photorespiration, dark respiration, leaf resistance, and transpiration exhibited no seasonal changes which correlated to the presence or absence of fruit. These data represent the first comprehensive examination of the effects of flowering/fruit formation on photosynthesis and photorespiration in perennial plants.Regulation of photosynthesis by fruit growth occurs in many plants, with photosynthetic promotion or reduction depending on sink demand. Other studies, however, have shown no correlation between photosynthetic rates and sink strength (cf 7). In apple (Malus domestica Borkh.), fruiting trees were shown to have reduced leaf weights (25) and leaf areas (1), but more total dry matter than nonfruiting trees (12), suggesting greater photosynthetic efficiency. In other studies, fixation of '4CO2 was usually greatest in leaves nearest the fruit, although sometimes the second nearest or even fruits further away received much of the labeled assimilates (10). Kazaryan et al. (18) also found the highest photosynthetic activity in leaves attached directly to the base of the apple pedicel and lower photosynthetic rates in leaves of nonfruiting branches of the same age. Wardlaw (29) noted that developing apple fruits always seemed to have priority demand over assimilates from adjacent leaves, whereas flowers and small or mature fruit had no effect on photosynthetic rates and attracted very little assimilates (4). From mid-June, the fruits in apple become strong sinks and may absorb nearly all assimilates from leaves on the same short shoot (spur). This suggests a pronounced fruit effect on photosynthesis during the period of intensive fruit growth (9,13 creases in apple due to the presence of fruit have not been consistent and have ranged from 40 to 400% (2,3,11,23).In general, changes in the components of net photosynthesis in fruiting trees are not well studied. In Citrus madurensis, dark respiration in fruiting and nonfruiting plants was similar (19), while Avery and Moore (3) found fruiting apple trees had lower dark respiration than nonfruiting trees, along with the lower stomatal and mesophyll resistances and increased transpiration rates. Others also recorded lower stomatal resistance (26) and higher transpiration rates (12) in fruiting apple trees.Photorespiration occurs three to five times faster than dark respiration in C3 plants and is a major ...

Fruiting Effects on Leaf Characteristics, Photosynthesis, and Root Growth in Peach Trees.

“…The percentages of the chloroplast compartment area per cross-section of a chloroplast from leaves of defruited trees were 48.8% in spongy cell and 50.5% in palisade cell, whereas the percentages were 91.4% and 83.5%, respectively, in leaves of fruiting trees. The Pn of leaves from fruiting and non-bearing trees are similar to that reported by Hansen (1970), Chalmers et al (1975), Fujii and Kennedy (1985), De Jong (1986), and Wood (1988. However, other researchers using other plant species have questioned the effects of carbohydrate accumulation in leaves on the photosynthetic rate (Ballantine and Forde, 1970;Wilkinson and Beard, 1975;Geiger, 1976;Hariri and Brangeon, 1977;Carmi and Shomer, 1979;Melis and Harrey, 1981;Lichtenthaler et al, 1982).…”

“…That photosynthetic rates differed between leaves of fruit trees with and without fruits is well known; fruiting actively promotes the photosynthesis of an individual leaf during the fruit maturation period (Chalmers et al, 1975;Fujii and Kennedy, 1985;De Jong, 1986;Wood, 1988). The reduction in Pn as a consequence of decreasing sink strength through fruit thinning is attributed to increased carbohydrate levels in leaves, a form of feed-back inhibition (Noel, 1970;Milford and Pearman, 1972;Thorne and Koller, 1974;Nafziger and Koller, 1976).…”

Vertically transmitted fungal endophytes: different responses of host‐parasite systems to environmental conditions

“…from storage tissues or mature leaves with positive net photosynthesis. Sink strength plays an important role in determining the level of resource intake in plants, since increased requirements of active meristems may result in an increased photosynthetic rate (Fujii and Kennedy 1985, Wardlaw 1990). In grasses, the endophytic mycelium is concentrated in the aerial parts of host plants and is closely associated with meristematic tissue (White et al 1993b), and some fungi are thought to be transmitted only vertically via host seeds (Schardl and Phillips 1997).…”

Influence of Elevated CO2and Air Temperature on Photosynthesis, Shoot Growth, and Fruit Quality of 'Fuji'/M.9 Apple Tree

“…3A and 8). 이는 과대지 잎이 정단신초의 잎보다 sink(과실)와 의 거리가 가까웠기 때문으로 생각되었다 Fujii and Kennedy, 1985 처리구가 가장 높았다 (Table 3).…”