Growth-recording instruments were used to measure extension growth of grass tillers under a variety of outdoor conditions. Variation in the rate of extension growth between tillers was fairly high, but nevertheless was found to be highly correlated with field temperature while only poorly correlated with light energy. By using these instruments, estimates of growth activity can be made rapidly and over relatively short periods of time; and it is suggested that the method may have use in assessing species for sensitivity to temperature.

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The effect of gibberellic acid sprays on' the winter growth of two pastures of Phalaris tuberosa L. differentially grazed for a period of four years prior to the investigation, was studied. The previously lightly grazed pasture had initially approximately ten times as much soluble carbohydrate in the underground parts as the heavily grazed pasture. Both pastures responded in the same way with an initial increase in yield with gibberelin but no subsequent increase. However, regrowth from cut areas treated with gibberellin was significantly greater on the lightly grazed pasture. Since the stubble remaining after cutting was very low in chlorophyll, it is suggested that the differential regrowth might be due to the higher levels of stored carbohydrate in the lightly grazed pasture.

1984) Control of iron chlorosis in apple trees with injections of ferrous sulfate and ferric citrate and with soil-applied iron-sul , ABSTRACT Chlorotic 'Red Delicious' apple (Malus domestica Borkh) trees located in Utah County, Utah, were treated for iron deficiency through pressure injection and soil treatment in September, 1981. Injection treatments were either ferrous sulfate (FeSO 4 · 7H 2 O) or ferric citrate (FeC 6 H 5 O 7 . H 2 O) at rates of 100 ml of 1% solution per year of tree age. Tne soil treatment was surface-broadcast acidified iron-rich mining residue (iron-sul) at approximately 1 kg per year of tree age. Cnlorotic conditions were completely eliminated by the spring of 1982 by ferrous sulfate injection. Ferric citrate injection decreased, but did not completely eliminate iron chlorosis. Visual observations were similar in 1983. The iron-sul treatment gave no apparent improvement of the chlorotic condition in the first season after treatment, and only slight improvement the second year. The improvement in chlorotic conditions gave correspondingly heavier fruit set, higher chlorophyll levels and greater shoot growth for trees injected with both ferrous sulfate and ferric citrate. However, even iron-sul significantly improved shoot growth and chlorophyll content compared to the untreated control. Some injury at the injection site was observed for both injected compounds. INTRODUCTION,

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