Ethephon (I) is used commercially to prolong the flow of latex from the rubber tree after tapping (Yield stimulation). The compound is applied to the bark in the region of the tapping cut and the effect on latex flow is due to the ethylene released by chemical decomposition, since gaseous ethylene itself is also a very effective stimulant. When 14C-I is applied to the bark of a young Hevea seedling, it is absorbed into the plant by processes which appear to be largely non-metabolic. Ethylene formation commences immediately at the site of application, and the gas is quickly translocated throughout the plant. Translocation of I to all parts of the plant also occurs and the accumulation of 14C in the bark above the zone of application is greater than that below. Chromatographic analysis has shown that compounds other than I remain in the plant tissue. Experiments using 14C-I have shown that detached leaves are able to convert a considerable proportion of the compound to at least twelve non-volatile acid products. One of these is a conjugate of I with an unidentified material. A major component of the products is 2-hydroxyethylphosphonic acid (II), which is itself converted to a number of compounds in leaves. The application of I to bark from mature Hevea, results in the formation of a single substance which is also a conjugate of I. Neither I nor II is effective in inducing the formation of ethylene from endogenous precursors in vegetative Hevea tissue. Ethylene is poorly metabolized by Hevea leaves and the evidence available indicates that it is unlikely that any of the compounds produced from I are metabolites of ethylene.

In July the yield of protein extractable from potato haulm could be 600 kg/ha and the beginning of September it is 200 kg/ha. The yield of fiber containing 1 to 2% N is less affected by maturity. The annual waste of extractable protein, suitable for feeding nonruminants, is about 60,000 tons. The contribution that some small changes in conventional potato husbandry might make to minimizing this waste is discussed.

Mechanical disintegration seems to be the most effective way of damaging the cells in potato tubers so that their juice can be expressed. If disintegration is too intense the pulp is intractable; a grater makes a uniform pulp with suitable texture. With existing continuous equipment it is necessary to press in two stages to get to 40% dry matter and further batch pressing is needed to get to 50%, but experience suggests it should be possible to make a press that would press to > 50% in one operation. Much less energy is needed to press out water rather than evaporate it. but about one-sixth of the tuber dry matter and more than one-half of the N is in the juice. Surplus, diseased, or damaged potatoes can be preserved for use as stockfeed by ensiling or drying. With the help of fungistatic agents such as ammonia or propionic acid, and if permanent preservation is not sought, it is not necessary to dry the tubers completely, and partial drying would cost less. We have therefore studied the practicability of pressing out fluid to the necessary extent instead of evaporating it off. Only small amounts of fluid can be pressed from sliced potatoes. The obvious methods for destroying the capacity of the tuber cells to retain fluid are: heating, chemical poisoning, freezing, and mechanical damage. Heating swells the starch so much that little water can be pressed from the cooked mass and chemical treatments were not studied because problems were envisaged in removing the agents from the products after pressing.Freezing is the traditional first step in making chuno on the altiplano of South America, where tubers are frozen in the open air at night and trodden during the day after thawing. After freezing at -i5°C and thawing, as much juice can be pressed from sliced tubers as can be pressed from mechanically disintegrated tubers, the thawed mass is sufficiently coherent to make pressing easy, and the juice removes less protein than juice made after mechanical disintegration. However, in spite of these real advantages, freezing does not seem to be as practical on a large scale as pulping because of the amount of energy consumed in freezing, which would be only partially recoverable.As tubers are damaged to increasing extents, the amount of juice that can be pressed out under the same conditions increases, but the pulp becomes an increasingly intractable paste that can be retained in a press only by wrapping it in filter cloth or in some similar way, which would probably not be practical on a large scale. The problem can therefore be formulated: to find a degree of damage that releases sufficient juice without producing pulp that is uncontrollable in a press. Experience gained in extracting protein from leaves is of limited assistance because the fibre in a leaf pulp gives it a texture that simplifies subsequent handling. If, as is probable, the conserved material is to be used as cattle fodder, the problem could be side-stepped by mixing some fibrous ruminant fodder, e.g.