Components of woody-tissue respiration in Abies amabilis

International audienc

Some preliminary notes concerning the impact of fossil fuel combustion on crop plants

A project concerning SO/sub 2/ effects on midwestern crop species is being pursued. Three 80' x 100' field plots of soybeans were periodically fumigated by controlled release of SO/sub 2/ through a system of pipes suspended over the plant canopy. The fumigations were performed on 24 days between early July and late August for an average of 4.75 hours per day. The 1978 experiment was similar with 5 plots exposed to 18 fumigations averaging 4.1 hours per day. The mean SO/sub 2/ concentrations during fumigation were 117, 300 and 786 ppB in 1977 and 94, 109, 192, 255 and 353 ppB in 1978. Only the plots receiving 786 ppB in 1977 and 353 ppB in 1978 exceeded the national secondary air quality criteria for SO/sub 2/. Some chlorosis and bronzing of leaf tissue were observed in the plot receiving 786 ppB of SO/sub 2/ in 1977, and mild chlorosis was observed in the 353 ppB plot in 1978; no other plots exhibited visible injury. However, bean yields were reduced in all the fumigated plots, regardless of whether or not visible injury occurred. The bean yield reductions were primarily due to decreases in seed size, a number of filled seeds per pod, and number of pods per plant. The effect of SO/sub 2/ fumigation on photosynthetic rate of leaf tissues was apparently contingent upon the age of the tissues, their prior exposure to SO/sub 2/ and the prevailing environmental conditions

Fruit-bearing branchlets are carbon autonomous in mature broad-leaved temperate forest trees

In order to evaluate the degree of carbon autonomy for fruit development, the carbon source-sink relationship in fruit-bearing branchlets of mature deciduous forest trees was manipulated in situ. The tests included half and complete defoliation, girdling or the combination of both treatments, which were applied on fruiting branchlets by using a canopy crane. Concentrations of non-structural carbohydrates (NSC) were analysed in different branchlet tissues and fruits, to identify situations of carbon imbalances induced by the treatments. NSC concentrations of branchlets were generally lower under treatments resulting in decreased fruit growth. All three investigated species (Carpinus betulus, Fagus sylvatica and Tilia platyphyllos) exhibited complete carbon autonomy of fruiting at the level of whole, undisturbed branchlets, since neither a decrease of total infructescence biomass, nor of individual fruit mass occurred on girdled, un-defoliated branchlets. On girdled, 100% defoliated branchlets, fruit biomass relative to controls decreased by approximately 50% in Carpinus and Tilia, but by almost 80% in Fagus, which can be explained by different proportions of photosynthetically active infructescence tissues among the species. In contrast to the other two species, Tilia branchlets did not import carbon to compensate for assimilate loss after defoliation