Sometimes the pollen of a plant lacks the facility of fertilizing its own ovules as well as those ovules of a closely related species a serious handicap to the plant breeder that occurs fairly commonly.

Self-incompatibilities in a number of varieties of Easter lilies has been overcome by Dr. S. L. Emsweller and Dr. Neil Stuart by the proper use of indoleacetic, indolebutyric, naphthaleneacetic, naphthaleneacetamide, parachlorophenoxyacetic, and 2,4,5- trichlorophenoxyacetic acids. Their work opened up new possibilities in breeding lilies and made it possible to produce new plant types unobtainable by usual breeding methods.

The growth regulators, applied at a concentration of 0. 1 to 1.0 percent, were mixed with lanolin to form a paste. A dab of the mixture is applied to a small wound made at the base of the ovary by merely breaking a flower petal where it is joined to the pistil.

AN EXCITING NEW development in plant research is the possibility of using chemicals as an aid in securing hybrid vigor.

Corn is an example of the increases in yields due to hybrid vigor. The unwanted or pollen-bearing male parts of the corn plants are large and easy to remove by hand or machine. Many of our crop plants bear pollen in such a way that they are difficult to remove, even by hand.

Scientists discovered that malefic hydrazide suppressed the growth of corn tassels. Perhaps, because of phytotoxiceffects on other parts of the plant, this effect could not be used practically.

Later, however, F. M. Eaton reported that the pollen mother cells in flowers of the cotton plant could be destroyed chemically without injuring the female parts of the flower. The chemical he found effective for this purpose, sodium-gamma, beta-dichloroisobutyrate, is called a gameticide, that is, a substance that kills gametes.

Water solutions of 0.2 to 0.4 percent concentration of this gameticide induced male sterility in cotton, and the plants set seed from pollen transferred from plants of another unsprayed variety growing nearby.

Favorable experimental results with the gameticide have been reported by R. A. Hensz and H. C. Mohr, of Texas Agricultural and Mechanical College, in experiments with watermelon. The Rohm & Haas Co. of Philadelphia, suppliers of the gameticide, have indicated that the results with apples, peaches, grapes, and strawberries were less promising.

Some plant-growth regulators are translocated into the developing seeds. Amo-1618 (2-isopropyl-4-dimethylamino-5-methylphenyl 1 -piperidinecarboxylate methyl chloride) suppresses the growth of some kinds of plants and causes them to grow as dwarfs.

Pole-type snap beans, such as Kentucky Wonder and Blue Lake, have been induced to grow as a bush type when the young plants were treated with Amo-1618. When the seeds produced by the chemically suppressed plants were sown, the resulting first generation plants were semidwarf. Seeds produced in the second generation, however, reverted to the usual pole-type growth habit.

Amo-1618 may be unusual in its ability to get into seeds.

The chemical 2,4-dichlorobenzyltributyl phosphate (Phosfon) also causes beans and certain other plants to grow as dwarfs, so that they resemble plants treated with Arno-1618. Applied to the roots or stems, it apparently is not translocated into seeds.

In experiments for comparative purposes, we collected seeds from Kentucky Wonder plants that we had treated with massive doses of Amo-1618 and from others that received Phosfon treatment. The seed from Amo-1618-treated plants grew as a bush type. Seed from the Phosfon treatment produced plants that were of the pole type, like the control plants.

The shattering of seed at harvesttime often causes a loss of 25 percent or more of the productivity of rice, beans, alfalfa, clovers, and like crops. Seed-bearing organs, pods, and capsules develop well-defined, thin-walled layers of cells, or abscission zones, as they mature. When the cells separate, the seeds are released, sometimes with surprising force, so that they may be physically thrown for some distance. Even a brief delay in separation of the cells would reduce losses from shatter and thus increase yields.

Since plant regulators generally bring about their effects by altering some physiological mechanisms within plants, it seems likely that those involved in seed shatter may be quite different from those concerned with the abscission of leaves, flowers, and fruit.

Chemicals, not of the growth regulator type, have. been used effectively to kill and desiccate crop plants and thereby reduce seed shatter. This practice, called spray curing, generally is accomplished with compounds used as herbicides or defoliants.

New regulating chemicals are being synthesized in laboratories, and other new regulators are being obtained directly from plants. Through further research with these compounds, additional ways will be found so that we can continue to use them safely and even more effectively in the production of seeds of high quality.

PAUL C. MARTH and JOHN W. MITCHELL are plant physiologists in the Growth Regulator and Antibiotic Investigations Unit, Agricultural Research Service, Beltsville, Md. Dr. Mitchell is Investigations Leader.