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Sulinary'. The klinetics of 14CO carboxylation and decarboxylation in corn root tips were determined to ascertain the sequence of product formation and subsequent utilization, and to obtain fuirther evidence to predict the enzymes mediating the carboxylation and decarboxylations. The carboxyliation data indicated that the first prodluct wa,s oxalo,acetate followed by malate and aspartate. Alalate was the first stable produict which could be detected. Decarboxylation data indicated that a large fraction of the 14CO., release and turnover of 14C was accountable for by a decirease in malate; however, e,ssentially all labeled amino acids turned over rapidly and at a greater rate than organic acids. The data generally su,pport the hypothesis that CO2 fixation in corn root tips is via P-enolpyruva'te carboxylase and malic dehydrogenase and that suibsequen,t malate metaholism is for the most part by direct decarboxylation, possibly by the malic eiizyme.In previotus work concerililg CO., metabolism in root tips, we o1)serv edl a rapid turnover of the fixed 14CO., which was correlated with a decrease in the main product, mal,ate (17,18

A review of the literature indicates that the stomates of leaves must be open for smog damage to occur (3,7,8,9,11). However, there is no direct relationship between degree of opening and extent of injury, nor has it been proven that injury is prevented when the stomates are closed. Moreover, most of the earlier work dealt with the reaction product of ozone and gasoline or ozone and an olefin (8,10,16 Because subsequent assays of plant leaf damage from the oxidant were desired, the rate of apparent photosynthesis was expressed on a nine-plant basis rather than on the leaf area or dry weight basis.

Boron is required for fiber growth and development in cotton ovules cultured in vitro. Incorporation of I''Clglucose by such fiber from supplied UDP-j''Clglucose into the hot alkali-insoluble fraction is rapid and lnear for about 30 minutes. Incorporation of I''Clglucose from such substrate by fibers grown in boron-deficient ovule cultures is much less than in the case with fibers from ovules cultured with boron in the medium. Total products (alkali-soluble plus alkali-insoluble fractions) were also greater in fibers from ovules cultured with boron. The fraction insoluble in acetic-nitric reagent was a small part of the total glucans; however, in the boron-sufficient fibers, there was significantly more of this fraction than in fibers from boron-deficient ovule cultures. The hot water-soluble glucose polymers from the labeled fibers had a significant fraction of the total I''Ciglucose incorporated from UDP-1'4Clglucose. Both f8-1,4-and 8-1,3-water-soluble polymers were formed in the boron-sufricient fibers, whereas the same water-soluble fraction from the boron-deficient fibers was predominantly 8-1,3-polymers. The incorporation of 114CIglucose from GDP-1'4Clglucose by the fibers attached to the ovules was insignificant. One of boron's possible roles in higher plant growth and development is that of regulating metabolic processes that result in the build-up of specific products, including UDP-glucose, glucose-1-P, or 6-P-gluconate (13-15, 22, 23, 34). If boron does play such a regulatory role, it would have some influence on cell wall metabolism including the biosynthesis of cellulose and pectin compounds. Torssell (44) proposed that the "complexes between boric acid and carbohydrates control the deposition of oriented cellulose micells and the accompanying stiffening of the cell wall." Spurr (39) observed that boron deficiency in celery plants did alter plant cell walls, and concluded that boron apparently affects the rate and process of carbohydrate condensation into wall materials. Odhnoff (26) also proposed that boron's influence on bean root cell elongation was probably related to the deposition of new cellulose microfibrils. Whittington (50) suggested that cessation of cell division in boron-deficient field bean radicles was related to abnormalities in cell wall formation which, in turn, prevented the cell wall from becoming organized for mitosis. Later work in the same laboratory (36) revealed that 1[4Ciglucose was incorporated into pectic substances of boron-deficient field bean radicles at a higher level than in boron-sufficient radicles. The authors proposed that boron's role in plant growth is as a bonding agent between cell wall polysaccharides. Wilson (51) also observed that boron deficiency affected cell walls of tobacco pith parenchyma grown in tissue culture by doubling the amount of cell wall fraction with no apparent change of the cellulose: pectic substance ratio as compared to control grown tissue. Boron enhanced the incorporation of myo-[3H]inositol into L-arabinosyl units from pectin of pea...