Showing papers on "Plant physiology published in 1969"

Plant root exudates

Abstract: Although the quantities of organic compounds exuding from roots is not large, seldom exceeding 0.4% of the carbon photosynthesized, they do exert a very strong influence on the soil microorganisms and may be significant in affecting plant nutrient availability. There is evidence that exudates from the roots of some plants are toxic to roots of neighboring plants and to the germination of some seeds.

Nutrient status effects on loss of amides and amino acids from pine roots

Abstract: Loss of amides and amino acids from pine roots was two and a half times greater from roots grown in phosphate-deficient nutrient solution than from those grown in complete nutrient solution and ten times greater than from plants grown in nitrogen-deficient solution. The major factor in increased loss from phosphate-deficient plants was an increase in free amides and amino acids in these plants. Increased amide and amino acid loss from phosphate-deficient plants may have important consequences in micro-organism—plant interactions.

Non-photosynthetic effects of red and far-red light on root-nodule formation by leguminous plants

Abstract: Nodulation of pea and broad bean plants grown in the light was found to be reduced when the roots were exposed to far-red light for 5–15 minutes daily during 5 consecutive days following inoculation with nodule bacteria. Similar results were obtained following a single exposure to far-red light during a period of 15 minutes at the 3rd or 4th day after inoculation. When the roots were exposed to far-red light either before inoculation or during the first two days afterwards there were either no effects or only slight effects on nodulation The inhibitory effect of far-red light on nodulation was partly reduced by subsequent exposure to red light, provided that the same part of the plant was exposed to both red and far-red light,viz either the root or the shoot. When different parts of the plant were exposed to red and far-red light respectively, there was no interaction between the two kinds of light on nodulation. Plants whose roots were exposed to far-red light did not subsequently show stem elongation. Nodules were found to develop on the roots of pea plants grown in the dark, provided that the plants were kept at or below 22°C. At 25°C nodulation was almost absent. Nodulation was decreased by addition of kinetin and IAA. In contrast to plants grown in the light pea plants grown in the dark, inoculated with either an effective or ineffective strain of Rhizobium, developed equal numbers of nodules. Exposure to red light slightly increased the percentage of nodulated plants but decreased the number of nodules per plant. Exposure to far-red light slightly decreased both the percentage of nodulated plants and the number of nodules per plant. The effect of far-red light was counteracted by red light andvice versa.

On the photosynthetic activity of developing apple fruits

Abstract: The effect of light on carbon dioxide and oxygen exchange was described in apple fruits. A photosynthetic activity of the fruit could be demonstrated in this way.