The results of the greenhouse tests are shown in Table II and expressed as a percent of yield or uptake of nutrients from the standard sources. The response to nitrogen or phosphorus of the standard fertilizers was two to five times that of the no-nitrogen or no-phosphorus controls, thereby assuring valid comparison among the different nutrient sources. RESULTS AND DISCUSSIONThese experiments clearly show that long-chain crystalline ammonium and potassium ammonium polyphosphates are effective sources of N and P. As shown in Table II, all of the long-chain polyphosphates were good sources of N, although N uptake tended to be slightly lower than from ammonium nitrate. The long-chain polyphosphates prepared from furnace acid gave responses equivalent to or higher than that of monoammonium orthophosphate, but those products made from wet-process acid were slightly less effective.Most of the long-chain polyphosphates were low in available P (citrate + water soluble) and one sample contained only 27 % of its total P in an available form, as shown in Table II. Thus, the conventional availability test indicates that these polyphosphates could not be useful sources of P for growing plants. In spite of their low rating in the availability test all were effective fertilizers, and the results from fine and granular sources showed the usual granule size response obtained from water-soluble P sources in Mountview soil. Apparently, the rate of dis-solution in the soil was sufficient to give agronomic response typical of water-soluble sources. Therefore, the conventional availability test is not valid for these longchain polyphosphates.This investigation has shown that long-chain crystalline ammonium or potassium ammonium polyphosphates may be readily produced by thermal dehydration of orthophosphates or short-chain polyphosphates, and these highly condensed phosphates are effective sources of N and P.

Su immary. Metabolism of the herbicide 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) was investigated in resistant corn (Zea mays L.) and sorghum (Sorghum zlvlgare Pers.), intermediately susceptible pea (Pisuim sativum L.), and highly susceptible heat (Triticum vulgare Vill.) and soybean (Glycine max Merril.). This study revealed that 2 possible pathways for atrazine metabolism exist in higher plants. All species studied were able to metabolize atrazine initially by N-dealkylation of either of the 2 substituted alkylamine groups. Corn and wheat, which contain benzoxazinone, also metabolized atrazine initially by hydrolysis in the 2-position of the s-triazine ring to form hydroxyatrazine. Subsequent metabolism by both pathways resulted in th-e conversion of the parent atraztine to more polar conmpounds and eventually into methanol-insoluble plant residue. No evidence for s-triazine ring cleavage was obtained. Both pathways for atrazine metabolism appear to detoxify atrazine. The hydroxylation pathway results in a direct conversion of a highly phytotoxic compound to a completely non-phytotoxic derivative. The dealkylation pathway leads to detoxication through one or more partially detoxified, stable intermediates. Therefore, the rate and pathways of atrazine metabolism are important in determining the tolerance of plants to the herbicide. Both quantitative and qualitative dififerences in atrazine metabolism were detected between resistant, intermediately susceptible, and susceptible species. The ability of plants to metabolize atrazine by N-dealkylation andl the influence of thhis pathway in determining tolerance of plants to atrazine are discussed.Two substituted s-chlorotriazines that are widely used today as selective herbicides for the control of annual weeds in fields of corn and sorghumii are 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) and 2-chloro-4,6-bis (ethylamino) -s-triazine (simazine). These compounds are effective inhibitors of the Hill reaction in photosynthesis (17) andl are known to reduce the rate of 14COo fixation in V!ants (3,24).Corn seems to be resistant to atrazine and simazine largely because of its abilitv to convert the 2 herbicides rapidly to noni-phytotoxic 2-hydroxy-4-ethylamino-6-isopropylamino-s-triazine (hydroxyatrazine) and 2-hydroxy-4,6-bis (ethylamino) -s-triazine (hydroxysimazine) (5,9,12,21). Other species have also been reported to metabolize atrazine (18) anlcl simazine (10) to their hydroxy derivatives. Tlle conversion of 2-chlorotriazines to their 2-hydroxy derivatives is probably non-enzymatic (5,12,20) anid appears to be correlated with the presence of a cyclic hydroxamate, 2,4-dihydroxy-3-keto-7-methoxy-1,4-benzoxazine (benzoxazinone), in plants (10).Sorghum, a resistant species, does not contain benzoxazinone and is nlot able to metabolize the chlorotriazine to the hydroxytriazinie (10). In the intcrmediately susceptible pea, atrazine was readily metabolized to the dealkylated derivative, 2-chloro-4-amino-6-isopropylamino-s-triazine (comp...

The primary atrazine-sensitive site seems to be located within the chloroplast for resistant as well as susceptible plants. Atrazine inhibits the Hill reaction and its associated noncyclic photophosphorylation, while being ineffective against cyclic photophosphorylation. N-Dealkylation causes a decrease in the inhibitory activity of atrazine, but the same reactions mentioned above were inhibited despite the change in molecular structure. Atrazine readily penetrates the chloroplasts of resistant as well as susceptible plants and seems to accumulate there until an equilibrium concentration is attained between the chloroplasts and the cytoplasm. In resistant plants such as sorghum, metabolism of atrazine very likely occurs outside the chloroplasts to form water-soluble compounds and insoluble residue, reduces the concentration of the photosynthetic inhibitor in the chloroplasts, and results in a recovery of photosynthesis. Changes in solubility of the parent atrazine, caused by its metabolism, may be of great significance in the tolerance of plants to the herbicide.

Abstract. The metabolism of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) in the resistant species, corn (Zea inays L.) and scrghum (Sorghum vulgare Pers.) was not the same. In corn, atrazine was metabolized via both the 2-hydroxylation and N-dealkylation pathways while sorghum metabolized atrazine zvia the N.dealkylation pathway. Atrazine metabolism in corn yielded the metabolites, 2-hydroxy-4-ethylamino-6-isopropylamino-s-triazine (hydroxyatrazine), 2-hydroxy-4-amino-6-isopropylamino-s-triazine (hydroxycompound I), and 2-hydroxy-4-amino-6-ethylamino-s-triazine (hydroxycompound II). None of these hydroxylated derivatives appeared as metabolites of atrazine in sorghum.Hydroxycompounds I and II were formed in 2 ways in corn: (1) by benzoxazinone-catalyzed hydrolysis oif 2-chloro-4-amino-6-isopropylamino-s-triazine (compound I) and 2-chloro.4-aminc-6-ethylamino-s-triazine (compound II) that were formed by N.deadkylation of atrazine and (2) by N-dealkylation of hydroxyatrazine, the major atrazine metabolite in corn. The interaction of the 2-hydroxylation and N-detilkylation pathways in corn results in the formation of the 3 hydroxylated non-phytotoxic derivatives of atrazine.Metabolism of 2-chloro-4-ethl-laiinio-6-isopropylamiiino-s-triazine (atrazine) in hligher plants was shown to be an important factor in herbilcidal selectivity. Detoxication of atrazine was reported to occur via the 2-hydroxylation and N-dealkylation pathways in higher plants (12). Corn is resistant to atrazine and 2-chloro-4,6-bis (ethylamino) -s-triazine (simazine) largely because of its ability to convert the 2 herbicides rapidly to non-phytotoxic, 2-hydroxv -4 -ethylamino-6-isopropyl-amino-s-triazine (hydroxyatrazine), and 2-hydroxy-4,6-bis (ethylamino)-s-triazine (hydroxysimazine) (1,2,5,10,12). The conversion of the 2-chlorotriazines to their 2-hydroxy derivatives is catalyzed non-enzymatically by a cyclic hydroxamate, 2,4-dihydroxy-3-keto-7-methoxy-1,4-benzoxazine (benzoxazinone) present in corn plants ( 1, 5, 9). The hydroxylation reaction appears to be correlated with the presence of benzoxazinone in different species (4,12). N-Dealkylation of atrazine occurred in higher plants to form 2-chloro-4-amino-6-isopropylamino-striazine (compound I) and 2-chloro-4-amino-6-ethylamino-s-triazine (compound II) (12,13,14). In resistant sorghum, only the N-dealkylation pathway was reported to be active, but in, corn both hydroxylation and N-dealkylation pathways were active.Autoradiographic evidence indicated that after a 48-hr atrazine treatment period, corn and sorghum yielded at least 1 common water-soluble metabolite of atrazine, but corn produced 2 other metabolites, neither of which was hydroxyatrazine (12).Hydroxylation of compounds I and II to fornm hydroxycompounds I and II (fig 1) is pos-sible in benzoxazinone-containing corn, but not in sorghum. N-Dealkylation of hydroxvatrazine (fig 1) could also occuir in corn to give hydroxyconu ounds I ande II. Such a reaction would not occur in sorghumi since atrazin.e is not conve...