Both carrot (Daucus carota L.) and common ragweed (Ambrosia artemisiifolia L.) plants metabolized 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron). Traces of all of the following derivatives of linuron were detected in both plants: 3-(3,4-dichlorophenyl)-1-methoxyurea, 3-(3,4-dichlorophenyl)-1-methylurea, 3-(3,4-dichlorohenyl)urea, and 3,4-dichloroaniline. Differences in absorption and concentration of these derivatives were observed between carrot and ragweed plants. All of the above derivatives were phytotoxic to common ragweed plants except for 3-(3,4-dichlorophenyl)urea and 3,4-dichloroaniline, while none of the derivatives were phytotoxic to carrot. In carrot, 87% of the applied linuron was metabolized to nonphytotoxic derivatives compared to only 13% in common ragweed plants. It appears that a combination of differences in absorption, metabolism, and phytotoxicity of several of the metabolite derivatives of linuron to carrot and common ragweed plants may be the primary reason for differences in sensitivity of these two plants to linuron.

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The ripening and eventual softening of fruits is a natural phenomenon. More knowledge concerning the chemical changes associated with ripening is necessary to improve the present handling techniques for maintaining the quality of fruits in fresh market channels. In this study, the chemical changes of several constituents in whole apples and tomatoes were ascertained at the unripe, ripe, and overripe stages of maturity to help explain the softening process.Objective measurements of fruit quality have as their goal the establishment of precise specifications to characterize any given lot of material. For example, measurements such as alcohol-insoluble solids, crude fiber, protein, acid content, and fruit pressure tests have been used by many workers for quantitative evaluation of the nutrition and quality levels of fruits and vegetables (3,5,10, If, 12,18,20,21,26). For many years, changes in the quantity and type (16) of pectic substances have been considered to play a role in ripening and firmness of fruits (7,13,15,19,22,25,27,28). Some evidence suggests that the pectic components of fruits may be hydrolyzed to soluble forms, with accompanying demethylation, and finally to smaller, less complex, units ( 4 ) . The mechanism involved in the transformation of these pectic substances as fruits mature, as well as their function in providing firmness to plant tissues, has not been clearly demonstrated. Older methods for extracting and analyzing pectic substances from plant material have been not entirely free from criticism (15). Recent methods (24) use less drastic extractions with little or no degradation, possibly yielding a product comparable to pectin in situ.This study seeks to provide fundamental information, using reliable methods, for a quantitative evaluation of some chemical changes associated with the maturation process of apples (Red Delicious and Stayman) and tomatoes (Brookston and Valiant). Especial attention is given to the determination and characterization of the pectic constituents. EXPERIMENTAL MATERIALS AND METHODSApple and tomato fruits. The fruits were obtained from orchards and plots at the University Farm during the 1953 and 1954 seasons. They were carefully harvested at the unripe and ripe stages of maturity with the ripe stage allowed to become overripe in the laboratory. Extremely large and small specimens were excluded as well as those with cracks or blemishes. The selection of fruits for analyses at the 3 stages of maturity was on the basis of skin color and firmness. Unripe fruits were full size but essentially green and were hard. Ripe fruits had full color change and were firm. Overripe fruits were similar to ripe, except senescence and softening had taken place, hence special care was required in handling them.

Amino acids and urea in the cultivated mushroom, Agaricus bisporus, were studied as changes in chemical composition may influence the nutrition and alter the quality of the mushroom. Amino acids were assayed by column chromatography, while urea, total nitrogen, and dry matter were determined by conventional methods in alcohol extracts and fresh tissues. Where gelatin was added to the compost, the amounts of alanine, ammonia, and arginine decreased, but aspartic acid increased. With the addition of hydrolyzed casein, arginine decreased. In the extracts, both the sum of the nitrogen in the various compounds and the total nitrogen by the Kjeldahl method increased toward the end of the growing cycle. Calculations showed 79% to complete recovery of nitrogen in the alcohol extracts. Mushroomshave for centuries been prized as a delicacy. They are known as a food of excellent nutritive value, low in calories and relatively high in proteins and amino acids.Fitzpatrick, Esselen. and Weir (5) found that the total nitrogen content was 0.5%, (fresh weight basis). of which 63% was in the form of protein. Workers at the University of Massachusetts investi-

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