Timing Of Defoliation Research Articles

Effects of Degree and Time of Defoliation on Yield and Related Attributes of Safflower1

From 1960–1962 four agronomically diverse safflower entries were grown in replicated field plots at Logan, Utah. These entries were partially or totally hand defoliated at seven stages of growth. Removal of all leaves — when averaged over dates, entries, and years — reduced yield by 23.0%, weight per 100 seeds by 7.7%, test weight by 2.6%, hull percentage by 6.0%, and increased oil by 6.9% in relation to the check plot. The increase in oil percentage was negatively correlated with the decrease in hull percentage (r= —0.86). Removal of leaves from the top half of the plant had a similar but slighter effect. Removal of branches from the bottom half of the plant reduced yield at the later stages of plant development. Removal of leaves from the bottom half of the plant regardless of growth stage did not affect the attributes measured. There was a differential response of safflower entries to the severe defoliation treatments (removal of all leaves or removal of leaves from the top half of the plant).

The influence of time of defoliation on the vigour of a tall grassveld sward in the next season1

Abstract The time of defoliation exercised a significant influence on both the production of the sward and the regrowth potential of Themeda triandra in the season subsequent to treatment. In the spring following treatment the regrowth potential of T. triandra and the actual sward regrowth followed similar trends. Highest spring yields were obtained after a cut during spring and summer while much lower yields were obtained following a cut during autumn and winter.

Studies on the Assimilation and Translocation of <SUP>14</SUP>CO<SUB>2</SUB> in Ladino Clover : IV. Utilization of reserve <SUP>14</SUP>C-assimilates by the plants in the early stages of regrowth

To determine the length of time in which newly developing organs depend upon reserve assimilates for their growth, the following experiments were carried out. Ladino clover plants were exposed to 14CO2 for 2 hours in an assimilation chamber. After 48 hours all plants were completely defoliated, selected plants were harvested at the time of defoliation and others were harvested 1, 3, 6, 9, 12, 15 and 18 days later. (The mean temperature during the experiments was 16.9°C). Harvested plants were radioautographed and the radioctivity of leaves which had developed since defoliation was measured with a gas flow counter. The experiments were performed 3 times. The major results and interpretation are as follows; 1) The specific activity of 14C in emergent leaves decreased rapidly in the first 6 days. and decreased slowly thereafter. This indicates that developing leaves depended on reserve assimilates only for about six days in these experiment. 2) Total activity of 14C in newly developing leaves continued to increase until 15 days after defoliation. In other words, reserve assimilates continued to translocate into the leaves until about two weeks after defoliation. 3) These result, together with those previously reported (Proc. Crop. Sci. Soc. Japan 36:269-274), indicate that emerging leaves are dependent upon reserve assimilate during their first week of development. Although they continue to utilize resesves during the second week, the young leaves are themselves exporting essimilates during this period and presumably are no longer dependent upon reserves.

Influence of untimely defoliation on the subsequent growth in some deciduous fruit trees. I

1. The effect of defoliation on the vegetative growth and flower bud formation was observed with young potted peaches, variety Okayama-wase, by removing all the leaves artifically at certain intervals during the growing season from June to October in 1959.2. When all the leaves were removed, terminal and secondary leaf buds came out from the axils and developed into new shoots, except on the trees defoliated in October. The earlier the defoliation, the sooner and the more the buds sprouted. These shoots grew so late in autumn that the leaves fell 30 to 50 days later than usual. Accordingly, the buds on these shoots sprouted late irregularly and ununiformly in the following spring. This tendency was most conspicuous in the trees defoliated on August 7.3. No flower buds appeared both on the trees defoliated in June and July, and some flower-like buds in August. However, on the trees defoliated after September complete flower buds were formed. The earlier the time of defoliation, the more decreased the number of flower buds per tree and the more ununiform the flowering time in the following year. The trees defoliated in September bloomed in October of the treated year, and those defoliated in August bloomed most abnormally in the following year.4. While the shoot growth was generally well in the treated year except the trees defoliated in July, the growth of the following year was strikingly bad except those defoliated in October. Moreover, the defoliation in July and August retarded the root growth greatly.5. From the results obtained, it is evident that in the Okayama-wase peaches flower buds were formed completely in September. These flower buds were already in the rest period in mid to end of September and leaf buds in October. And so the trees defoliated untimely in previous growing season showed “prolonged dormancy”.

Influence of Nitrogen Fertilization and Clipping on Grass Roots

AbstractStrategic placement of P32 and root excavations revealed that roots of orchardgrass and bromegrass reached a greater depth when no N was applied. Nitrogen increased the root diameter and decreased the rate of elongation causing the plants to feed near the soil surface for a longer period of time. Defoliation stopped root growth within 24 hours and induced decomposition of the existing roots within 36 to 48 hours. Uptake of P32 placed in the existing root zone 24 to 48 hours after clipping was not detected until new roots reached the activated zone. New roots were initiated from basal leaf nodes of orchardgrass and rhizome nodes of bromegrass. Removal of all roots at the time of defoliation did not influence the rate of regrowth from transplanted sod plugs under optimum soil moisture conditions.

Studies on Flowering and Fruiting of Leguminous Crop Plants : VI On growth, yields and changes of chemical constituents in soybean plants induced by periodic phosphorus deficiency

This experiment was conducted to study the effects of periodic phosphorus deficiency on flowering and fruiting of soybean plant (using Shirobanasai No. 1). The results obtained were as follows : 1. The effect of phosphorus deficiency ih the beginning and end of flowering time on dry weight was so severe that even if phosphorus was sufficiently supplied thereafter, it was extremely difficult to recover. 2. It was observed that there was a high correlation between the time of defoliation and the concentration of not only P2O5 but also that of total N, total sugar, and starch in petiole just prior to yellow leaf stage. 3. P2O5 deficiency was observed to decrease the number of node of branch. 4. Phosphorus deficiency after fruiting time reduced the contents of total N and P2O5 in the vegetative organ, and increased the concentration of total sugar and starch, increasing the yields. Therefore, P2O5 supply after fruiting time was ineffective te increase the yield.