Tubers of sago pondweed (Potamogeton pectinatus L.) were grown at 72 F in a 14-hr photoperiod under 400 ft-c of coolwhite fluorescent illumination. Plants were randomly harvested each day for 30 days, the organs individually weighed, and carbohydrate determinations made on selected tissues. Unsprouted tubers averaged 19.5% dry weight of which 74% was carbohydrate, predominantly in non-extractable form. During growth, the carbohydrate supply in the tubers decreased logarithmically by ½ each 4.93 days. Shoots began to grow logarithmically at 11 days, doubling in dry weight each 4.5 days. After 18 days, the carbohydrate content of the main shoot increased logarithmically, doubling each 7.35 days. Plants produced from average tubers increased 7-fold in dry weight in 30 days. Growth analysis showed that no shoots became self-sufficient before 16 days. Deduced patterns of carbohydrate flow are correlated with reports of herbicidal effectiveness.

The relative tolerance of one-year-old peach and apricot seedlings to 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) and 2-methoxy-4,6-bis = (isopropylamino)-s-triazine prometryne was established by soil surface and soil incorporated applications. In all cases, the relative tolerance to both herbicides was greater for peach than apricot. Reciprocal grafts of peach and apricot budded seedlings indicated that the rootstock did not alter the tolerance. The greater tolerance of peach over that of apricot was attributed to physiological detoxification occurring in the scion.

A low-volume, transparent, acrylic plastic concentrate tank for herbicide spray solutions is described which includes a fast-opening filler valve, a pressure relief valve, and a compressed air intake.

Mathematical relationships are developed for a general system in which the concentrate chamber and diluent vessel contain the active material to be evaluated. The use of the system for increasing the effective half-dosage distance is illustrated. A technique is described for decreasing the half-dosage distance with a conventional system.

Using previously published data, a quantitative treatment of the influence of soil moisture content on herbicidal activity has been described. The treatment is based upon the use of the distribution coefficient, Kp, and is an extension of recent developments in the application of chromatographic theory to movement and sorption of chemicals in soil.

The effectiveness of catch or trap crops in ridding soil of witchweed was studied by growing the crops 1 through 5 years on heavily infested witchweed land.

Catch or trap crops were about equal in value for witchweed eradication. Soybeans, field peas, and sorghum were grown 3 years before acceptable corn yields were obtained. Two years of millet and 4 of corn were required to obtain acceptable corn yields.

Complete eradication of witchweed was not achieved by any crop during the 5-year period.

In 1963 and 1964, a study was conducted near Bernardo, New Mexico, on control of saltcedar (Tamarix pentandra Pall.), comparing single and combination mowing and spraying with the propylene glycol butyl ether (PGBE) ester of 2-(2,4,5-trichlorophenoxy) propionic acid (silvex), repeated spray applications of silvex, and single applications of mixtures of silvex and 4-amino-3, 5,6-trichloropicolinic acid (picloram). None of the mow-spray combinations initiated in 1963 reduced the stand of saltcedar more than 8%, and there were no significant differences between treatments. A follow-up spray treatment of 4 lb/A of silvex in 1964 increased the plant kill up to 60%. Spraying undisturbed saltcedar in June, 1964, and re-spraying in August with 2 lb/A of silvex, reduced the saltcedar approximately 40%, as did a single application of a mixture of 2 lb/A of silvex and 2 lb/A of picloram in June.