Staminate Catkins Research Articles

Pinosylvin Methyl Ether Deters Snowshoe Hare Feeding on Green Alder

Pinosylvin methyl ether (PME), a toxic phenol, is a potent deterrent to showshoe hare feeding on green alder. Concentrations of PME found in green alder parts can account for the low palatability of winter-dormant foliar buds and staminate catkins but cannot affect internode palatability. The lack of a PME-related defense system in internodes suggests that green alder has at least a two-level defense system: defense of growth stages and defense of parts within growth stages.

The role of endogenous growth regulators in the differentiation processes of walnut (Juglans regia L.)

The character of endogenous growth substances was investigated in developing buds, young fruits and mature walnut leaves. The relatively high content of auxins and gibberellin-like substances was found by means of bioassays in the youngest primordia of vegetative buds. The level of auxins drops in the further course of primordia transformation into the staminate catkins. The development of leaf-buds is characterized by the accumulation of inhibitory activity as revealed by theAvena bioassay, whereas the data obtained from the lettuce bioassay indicate a pronounced stimulation. The onset of terminal bud development is also accompanied by inhibitions and it is only with pistillate flower differentiation that the temporary rise in auxin level is observed. An inhibitory activity was found in these extracts using lettuce bioassay. There is a relatively high auxin level in young fruits, mature leaves and resting buds during the mid-summer period whereas the accumulation of clearcut inhibitions is signalled by the results of lettuce bioassay.

The role of growth regulators in the differentiation of walnut buds (Juglans regia L.)

The character of endogenous regulators in walnut buds was followed by means of bioassays in the course of vegetation. It was ascertained that a rise in the level of gibberellin-like substances precedes the sprouting of buds. The origination of new buds in the axil of young leaves is accompanied by a fall in the level of auxins, by a low gibberellin content and by the presence of inhibitors. In this situation the primordia of staminate catkins are diferentiated in the basal buds. The vegetative buds which are formed in the axils of further leaves, stop developing because of the accumulating inhibitors. Towards the close of vegetation the primordia of pistillate flowers originate in terminal buds and their differentiation is accompanied by a substantial rise in the level of auxin-like substances, while some of the inhibitors keep asserting themselves. On the basis of these findings we have tested the possibility of affecting the differentiation of staminate primordia and of vegetative buds by the exogenous application of selected regulators. Spraying young leaves with IAA and MH solutions will increase the number of vegetative buds in the twigs. A later spray of other twigs by TIBA and GA3 solutions will increase the number of staminate buds.

CHESTNUT BREEDING, TECHNIQUES AND RESULTS

Chestnut breeding, to develop vigorous, blight-resistant timber trees, began in the Division of Forest Pathology, Bureau of Plant Industry, Soils, and Agricultural Engineering, U. S. Department of Agriculture in 1909 and is continuing. In the period 1925–49 more than 6,000 hybrids were grown. About 40 percent of the total possible number of combinations of crosses between the L3 soecies of Casta have been made successfully, indicating the close relationship existing between the species. The period of receptivity of chestnut stigmas was determined as beginning a few days after the staminate catkins began to blossom, reaching its highest degree about 12 days later, and extending nearly three weeks. Pollinations made in the morning were more effective than those made in the afternoon. Attempts to obtain viable seed by self-pollinating pistillate flowers whose styles were clipped off failed; however, viable seed was obtained by cross- pollination. Tests designed to prevent insects from visiting flowering twigs on which all staminate flowers had been emasculated showed that chestnut is wind-pollinated. Exposed pollen on anthers is at first tacky, but air currents soon dry the pollen and, together with the movements of insects feeding on the pollen and nectar of the catkins, it is dislodged and is airborne. Inheritance of blight resistance probably is controlled by two pairs of genes. Early flower ing is dominant over late flowering. At Glenn Dale, Md., temperature departures from the mean for April, and occasionally for April and May, determine when flowering begins. Time of nut drop in chestnut is inherited without dominance. Time of flowering determines the time of nut drop. Size of nuts is inherited with incomplete dominance, tending to approach the nut size of the parent producing the smaller nuts. The everbearing character found in C. seguioii is inherited iii at least a 3 : 1 ratio in the second generation. First-generation hybrids from crossing a selection of C. mollissima with C. dentata appear promising for planting as forest-timber trees. On a poor site they have grown at the rate of 2.8 feet per year for 10 years. Their blight resistance is sufficient to warrant test ing them on forest sites. Scions of Japanese chestnut carrying the mutation “spineless” were grafted and later crossed with other Castauca species. The mutation “cracked-bark,” wherein the bark of chestnut trees begins to crack at the age of three or four years, was obtained in first- generation hybrids from a C. mollissimaC. dcntata cross. Stunted growth, a general drooping of the branches, and an increased susceptibility to blight and to winter injury are associated with cracked bark. An anomaly, “naked chestnut,” was observed in certain hy brids: the burrs stop developing at an early stage while the nuts continue normal develop ment, so that the green nuts are exposed. The anomaly occurs in certain years and probably is a nonheritable mutation. Chestnuts, chinkapins and hybrids graft readily, but are difficult to bud. Extensive investigations have failed to develop an efficient method of rooting cuttings.

Botanical Notes: 1948

A black walnut tree on our town property yielded bushels of hulled nuts in 1947. There was an abundance of staminate catkins this year but, by actual count, there were but sixty-two nuts. Viola pedatifida returned in measurable numbers after a decided scarcity. We were pleased to find a fair number of plants of Spiranthes ochroleuca, a somewhat rare but attractive member of the orchid family. These grow not far from Emporia. Farmers welcomed a heavy crop of the big bluestem-Andropogon furcatus. This grass seeded well also. Our elm trees were very badly treated. Heavy storms broke off many limbs and even some trees were destroyed by wind. The city had undertaken to spray elm trees for several previous years against the leaf-eating worms, Paleacrita and Aleophila. This season it was not possible to do this satisfactorily and one result was the denuding of some trees so completely that they were in a bad condition. They appeared also to have been attacked by some kind of fungus; consequently many of the owners have banded their elm trees this season. In addition, the city is spraying the trunks near the ground with DDT. The results will be observed with much interest.

Offspring of a Self-Pollinated Reversed Carpellate Plant of Morus alba

In I929, the writer published the results of a breeding experiment with self-pollinated seeds obtained from a staminate plant of Morgs alba L. which had several branches showing sex reversal to femaleness (2). The progeny from these seeds consisted of pure staminate individuals, pure carpellate individuals, and individuals with mixed sex expression at the first blooming period. It was evident, therefore, that in the white mulberry an individual originally determined as a pure male had the potentialities to produce offspring of both sexes without the introduction of any new hereditary units from the outside. Sex reversal had been seen previously in carpellate plants but no trees were available at this time for experiment, although young trees were being grown in order to make a definite study of reversal to maleness in carpellate individuals. These young trees were transplanted from the greenhouse to the botanic garden, and in I932 a carpellate plant showed several small branches with reversal to maleness, developing a few staminate catkins. These branches were inclosed with some carpellate branches with cloth to keep out all foreign pollen, and a small quantity of selfed seeds was obtained. These seeds were dried for a few days and then planted in the greenhouse. The seedlings developed vigorously in a long-light photoperiod during the winter, and the next spring (I933) they were planted in rich soil in the garden. In the meantime, the spring of I934 was very dry and the original parent tree, now ten years old, bloomed abundantly and showed a decided increase in the number of reversed branches and the number of staminate catkins and flowers. Nearly all of the main branches of the tree now developed some staminate catkins. There was a decided gain in maleness in this tree since the spring of I932. In the regions of sex reversal many of the catkins were poorly developed, with part of the flowers either vestigial or distorted. In some cases ovularies were found with imperfect anthers developing in their sides.

Progeny Resulting from Self-Pollination of Staminate Plant of Morus Alba Showing Sex Reversal

1. A reversed staminate tree of Morus alba was self-pollinated and produced good seed from which thirty-two young trees were grown. Of these the first six to bloom had sex expression as follows: one tree was pure staminate for two years; one was pure staminate the first year and of mixed sex the second year; two were pure carpellate; and two were carpellate with a slight development of staminate catkins. 2. Determination of the sex of the original male parent, therefore, was not due to any sex-determining differential heredity present, since it proved to have the potentialities for both sexes, as shown by the reversal in its soma; and the sex of the offspring was also determined in the zygote as male and female, through a physiological gradient which caused a male or a female state to be differentiated in the same manner as and through the same cause as that which induced these states to develop through sex reversal in the advanced ontogeny of the individual. Sex-determining factors and sex-determining chromosomes can have no correspondence with the phenomena brought out by the experiment.