Plants Of Different Ages Research Articles

Low temperature effects on growth and physiology specific to a "grass-clump" dwarf wheat hybrid

The growth habit of "grass-clump" dwarf wheat plants can be affected by extremely short 16° treatments if given repeatedly. To localize the earliest growth responses in plants of one such hybrid (Mql × KF 1), the temperature sensitivity of plants of different ages, and the earliest temperature-induced changes in growth, development, and shoot physiology were investigated and compared with the responses of normal wheat plants.Mql × KF 1 plants growing at 26° responded to progressively shorter 16° treatments as they aged and plants exposed to 16° after 10 days growth at 26° were unable to recover from low temperature treatments of 3–5 days duration. Although shoot growth (as dry weight) of Mql × KF 1 stopped abruptly after 7 days at 16°, root growth (as dry weight) continued for at least 15 days. The rates of CO2 and water vapor exchange in individual leaves responded to low temperature similarly in both the dwarf and normal plants and did not markedly decrease until after 4 days at 16°. The most rapid low temperature response specific to Mql × KF 1 plants was cessation in primary tiller development immediately after the beginning of 16° exposure. It is proposed that the primary 16° effect is on the shoot meristematic region and that other changes in growth and physiology result from the lack of meristematic activity in the young growing region.

Effects of Cultivar and Plant Age on Vegetative Growth of the Strawberry, Fragaria ananassa

Growth of strawberry plants (Dunlap, Sparkle, and Catskill) in the greenhouse was affected by the time of rooting of the runners in the field. This was shown by more rapid leaf and leaf-area production, larger leaf size, more runners and root growth on the older compared to the younger runner plants. The oldest plants also produced the greatest number of flower buds, but the time of bloom was not appreciably affected. The growth responses of plants of different sizes were similar to those of plants of different ages. These growth responses were most apparent during the first stages of growth, but the resulting differences frequently persisted for several months. Significant differences between cultivars were also found. Initially the greatest leaf size and leaf area were produced by Catskill plants. Because of a higher leaf production rate, Sparkle plants eventually had the largest leaf area. Sparkle plants were the last to flower and also to initiate runner production. Dunlap plants were the first to flower and produced the largest number of flowers. In the field, leaf production records indicated responses from cultivars and plant age similar to those found in the greenhouse.

EFFECTS OF CULTIVAR AND PLANT AGE ON VEGETATIVE GROWTH OF THE STRAWBERRY, FRAGARIA ANANASSA

Growth of strawberry plants (Dunlap, Sparkle, and Catskill) in the greenhouse was affected by the time of rooting of the runners in the field. This was shown by more rapid leaf and leaf‐area production, larger leaf size, more runners and root growth on the older compared to the younger runner plants. The oldest plants also produced the greatest number of flower buds, but the time of bloom was not appreciably affected. The growth responses of plants of different sizes were similar to those of plants of different ages. These growth responses were most apparent during the first stages of growth, but the resulting differences frequently persisted for several months. Significant differences between cultivars were also found. Initially the greatest leaf size and leaf area were produced by Catskill plants. Because of a higher leaf production rate, Sparkle plants eventually had the largest leaf area. Sparkle plants were the last to flower and also to initiate runner production. Dunlap plants were the first to flower and produced the largest number of flowers. In the field, leaf production records indicated responses from cultivars and plant age similar to those found in the greenhouse.

LEAF RESISTANCE IN A GLASSHOUSE TOMATO CROP IN RELATION TO LEAF POSITION AND SOLAR RADIATION

SummaryLeaf resistances were measured in a glasshouse tomato crop, using a mass flow porometer. With plants of different age the sixth to eleventh leaf from the top of the plant had the lowest leaf resistance, both within the stand and at its perimeter. Full leaf expansion occurred at the twelfth to fourteenth leaf. Older leaves had high leaf resistances, especially within the crop.Raising the CO2 concentration of the glasshouse to approximately 1000 vpm tended to increase leaf resistance but this increase was seldom significant and was sometimes not observed at all.On sunny days, leaf resistances were higher for much of the day than resistances on dull days. This was believed to be due to a form of the midday stomatal closure observed in some plants under high insolation.

Physiological and ecological studies on the oestrogenic isoflavones in subterranean clover (T. subterraneum L.). VI. Effects of defoliation including grazing

The effects of defoliating plants of different ages in different ways on the isoflavone content of the remaining leaves were investigated. When the fully expanded leaves were removed from 3-month-old plants, formononetin and genistein were reduced and brochanin A was unaffected in leaves which expanded during the subsequent 10 days. In seedlings, all three isoflavones were reduced in concentration following defoliation. But when young leaves were removed from seedlings, the isoflavones in the older remaining leaves were increased. It is suggested that severe defoliation affects soluble carbohydrate levels which in turn affect the synthesis of the isoflavones. Continuous grazing with 3–7 breeding ewes per acre had little wffect on isoflavone levels in fully expanded clover leaves.

Cytological Effects of Pesticides

The meiotic effects of the insecticide N-methyl-1-naphthyl-carbamate “Sevin” were tested by spraying flower buds of Vicia faba plants of different ages with the insecticidal solution for different periods of time, recovery experiments were also conducted. It was found that the percentage of abnormal PCM's increased by increasing the No. of sprays then decreased by increasing the time of recovery. Stickiness lagging chromosomes, and other irregularities were effected by “Sevin” in meiosis. Polyploid PMC's were also induced by different treatments with “Sevin”. The different treatments with “Sevin” did not induce pollen sterility.

Exploration on Phenotypic Correlation Coefficient among Main Characters of Tea Plant for Breeding Selection

1. By using clones of 170 hybrid. individuals, the correlation coefficients between combined main characters were calculated with parents and their clonal plants of different ages.2. Owing to the data of the past examinations and the calculated values including both the environmental and genetic variance in this design, any problem with those tested years, especially, the climatic differences could not be recognized.3. But some relations between such characters as above mentioned could be certained by this preliminary research, so further studies are expected.4. Most of the clones, used in this research, were so young for general tea-life, that we have been going to have more times of replication with larger number of clone.5. The results are generally summarized as follows.a) Morphological characters of tea-leaf look to be fixed in the comparatively young ages. That is, they are thought to be high repeatable.b) The relations between their characters of parent and its clonal plants were seen as like as the previous description, even though the clonal plants were very young.c) With younger plants after setting, the correlation between the cold damage and the plant-age was significant on five percent level.d) The correlations between paired characters were high with two kinds of shoot at a different stage, one of them had one bud and four leaves, and the other one bud and five leaves.e) The correlation between two kinds of damage devided with the external appearance on leaf in cold and dry winter could hardly been found.f) In connection with the winter damage, only the leaf-type showed a large coefficient of correlation between plant ages or between parent and its clonal plants, but not among the other characters.g) The authors will have to study, in future, with more numerous combinations, on the genetic correlation and heritability excepted the environmental variance.h) The correlation coefficients between the characters of young tea plant before setting are clearly different one another with the different combinations pollinated, and owing to taking care of the genic combination, linkage and so on the authors expect to test combining ability or to do selection by every combination.i) On the correlation after setting, the rooting-ratio may be variable on account of transplanting. Then the authors must take charge of the advanced research in future.j) From the technical point of view, the authors will need to use fifty individuals every other combination at least, as materials for such a calculation. And, further more, theoretically, the authors would want one hundred or two hundred individuals.On this point, the authors intend to study on the other day, taking counsel with their staffs.

Absorption of P-32 by Leaves of Glycine Max of Different Ages

Absorption of phosphorus-32 by the leaves of soybean plants of different ages was studied. It was shown that absorption by the leaves including the cotyledons was greatest by immature leaves and absorption decreased with increasing leaf age till a fairly steady state was reached. Immature second and third trifoliate leaves did not translocate phosphorus, but applications of P-32 made to young cotyledons and primary leaves did result in phosphorus transport.

Desiccation curves of root tissue and the problem of the delimitation between free and bound water

Statmographs were used for determining the curves of weight decrement of severed root tips of the squash (Cucurbita maxima L.) with time and were examined under controlled conditions. The existence of two qualitatively different fractions of water could not be demonstrated by the method used, all the curves obtained displaying a completely continuous character, without any inflexion point. The basic shape of the curves remained preserved on desiccation at different temperatures (20–40° C), at different relative humidity (45–90%), with plants of different age and different composition of aqueous media (Knop's nutrient solution, calcium-free medium, distilled water). Not even a 0·01% solution of potassium humate which significantly raised the water content of root tissue affected the shape of the desiccation curves. A continuous release of water was also observed when the meristematic root zone and the zone of longitudinal growth were dried separately.

Factors affecting the growth of carnation plants from shoot apices

SUMMARYCarnation plants were grown from shoot apices ranging from 200 μ to 1 mm. in length, derived from plants of different ages, at all times of the year. Tips grew best in small tubes on a simple nutrient medium, supported on wicks of ashless filter paper. The presence of rooting hormone in the medium was essential during the early stages of culture. Rooting was affected by the size of the tips and the time of year at which they were excised. Rooting of tips after heat treatment of the parent plants differed with variety, and virus infection also affected the rooting of some varieties.

SHOOT TIP ABORTION IN ULMUS AMERICANA

Millington, W. F. (Marquette U., Milwaukee, Wis.) Shoot tip abortion in Ulmus americana. Amor. Jour. Bot. 50(4): 371–378. Illus. 1963.—Phenological observations of American elm have shown that the phenomenon of shoot tip abortion in which the distal several plastochrons of each shoot turn yellow and abort, inducing sympodial growth, occurs over a period of several weeks starting at the time fruits are shed from older trees. Time of abortion varies among plants of different age, among individuals of the same age, and among shoots on the same individual. In the latter case, time of abortion is inversely correlated with the vigor of the shoot, the most vigorous shoots on a branch being the last to abort. Abortion is first evident in the yellowing of the entire shoot tip. Cytohistological studies show that necrosis commences at the sixth to eighth node back of the apex, where it is apparent in autolysis of internal cells of the stipules. Necrosis progresses acropetally in the stipules and young leaves and ultimately involves the leaf primordia at the shoot apex. Mitosis ceases in the shoot apex and its meristematic appearance is lost. These changes follow in basipetal sequence in the axillary buds down to the bud below the abscission site. This bud remains active and will resume growth the following season. The abscission site is evident externally as a green‐yellow boundary in the basal part of the internode. No protective layer is present at the time of abscission, but it develops after the shoot tip abscises. There is no indication of blocking of vascular tissues before shoot tip abortion and limitation of water supply probably is not a causal factor. Photoperiod studies show that shoot tip abortion is accelerated in short days and delayed but not prevented in long days. Greenhouse experiments show that abortion is delayed also in seedlings, in plants supplied with organic fertilizer, or grown with the roots unconfined. Plants grown in a nutrient solution deficient in nitrogen aborted ahead of controls and plants deficient in calcium. Although shoot tip abortion occurs coincident with fruit drop, there is no indication of a causal relationship. The literature relating to shoot tip abortion is discussed in relation to the above observations.

Shoot Tip Abortion in Ulmus americana

Millington, W. F. (Marquette U., Milwaukee, Wis.) Shoot tip abortion in Ulmus americana. Amor. Jour. Bot. 50(4): 371–378. Illus. 1963.—Phenological observations of American elm have shown that the phenomenon of shoot tip abortion in which the distal several plastochrons of each shoot turn yellow and abort, inducing sympodial growth, occurs over a period of several weeks starting at the time fruits are shed from older trees. Time of abortion varies among plants of different age, among individuals of the same age, and among shoots on the same individual. In the latter case, time of abortion is inversely correlated with the vigor of the shoot, the most vigorous shoots on a branch being the last to abort. Abortion is first evident in the yellowing of the entire shoot tip. Cytohistological studies show that necrosis commences at the sixth to eighth node back of the apex, where it is apparent in autolysis of internal cells of the stipules. Necrosis progresses acropetally in the stipules and young leaves and ultimately involves the leaf primordia at the shoot apex. Mitosis ceases in the shoot apex and its meristematic appearance is lost. These changes follow in basipetal sequence in the axillary buds down to the bud below the abscission site. This bud remains active and will resume growth the following season. The abscission site is evident externally as a green-yellow boundary in the basal part of the internode. No protective layer is present at the time of abscission, but it develops after the shoot tip abscises. There is no indication of blocking of vascular tissues before shoot tip abortion and limitation of water supply probably is not a causal factor. Photoperiod studies show that shoot tip abortion is accelerated in short days and delayed but not prevented in long days. Greenhouse experiments show that abortion is delayed also in seedlings, in plants supplied with organic fertilizer, or grown with the roots unconfined. Plants grown in a nutrient solution deficient in nitrogen aborted ahead of controls and plants deficient in calcium. Although shoot tip abortion occurs coincident with fruit drop, there is no indication of a causal relationship. The literature relating to shoot tip abortion is discussed in relation to the above observations.

The effects of chronic gamma irradiation on the growth of kalanchoë cv. “brilliant star”

Kalanchoë seedlings were exposed chronically to 330 r/20-hr day from a Co 60 source. Samples were harvested weekly. No new leaves were produced after initial exposure to irradiation, with mitosis in the apical meristems apparently suppressed, but the axillary meristems and the cambium continued their activity. This resulted in a much broadened stem tip with enlarged cells, supported by a stout internode in which cell size had remained relatively normal but cell number had increased. After about 26 days of exposure, meristematic activity in the shoot apex region resumed and resulted in the formation of growth centers which gave rise to leaves or malformed structures. The original phyllotaxy was not recovered. It is suggested that the resumption of growth may be an instance of adaptation to irradiation. In a second investigation the effect of chronic irradiation at various dose rates and on plants of different ages was tested. The dose rates used were 10, 25, 50, 100 and 250 r/20-hr day. Plants were in leaf stage 6, 8, 11 and 16 at the beginning of the experiment. No obvious age effect could be determined over this range of leaf stages. At 10 and 25 r/day the rate of leaf production did not appear to be affected. At 50 r/day about five more leaf pairs were formed before normal activity of the apical meristem ceased. In heavily irradiated plants leaves tended to be larger, broader and heavier. Much of this increase resulted from the production of more cells rather than larger cells. Internodes which were formed during irradiation showed a reduction in length, largely because in these fewer cells were formed. The degree of reduction was dependent upon dose.

THE EFFECT OF TIME OF APPLICATION OF NITROGENOUS FERTILIZER ON POWDERY MILDEW OF WINTER WHEAT

Applying nitrogenous fertilizer (N) to wheat plants of different ages affected the incidence of powdery mildew, Erysiphe graminis DC, differently. When N was applied before the flag leaf had emerged, the infection‐index (number of pustules per 100 sq.cm. of leaf blade) increased to a maximum and then declined. If N was applied after the flag leaf had emerged, the infection‐index increased steadily without reaching a peak, and the increased susceptibility was not associated with an increased relative leaf growth rate as when N was applied earlier.The integral of the number of pustules per unit area with time, and the number of perithecia on the leaves of the main stem, both increased with increasing delay in the application of N. Plants given N in either April or May had at least three times as many pustules as those given N in January. The time when N was applied did not affect the date when perithecia appeared.After adding N to nitrogen‐deficient plants, the already mature leaves which had resisted mildew infection, became susceptible. This change is not associated with changes in the epidermal wall.

玉葱品種の早晩生について

1. The data reported in this paper include the results of studies of the effects of temperature, photoperiod and age of plant on bulb formation of 11 Japanese and 10 American onion varieties planted in the fall of 1951 at Nagano (360 m) and in the spring of 1952 at Sugadaira (1, 250m).2. In Aichishiro, an extra early variety, bulb developed even under short day conditions of 10-12 hours if temperature was faborable and plant had grown to certain size. In Senshuki, a midseason variety, and Sapporoki, a late variety, bulb did not develop under the same conditions.3. In Aichishiro and Kaizuka-gokuwase, both extra early varieties, plants which were sown in the fall, did not develop their bulbs in spring in spite of the sufficient day length for bulb formation.4. Increasing the day-length to 16 hours accelerated bulb formation and topdown in the middle and late-season varieties, some of which did not down their tops completely under the natural day-length at Nagano.5. Under the deylength of 13 hours, time of topdown was accelerated by high temperature in the early varieties, but was not accelerated in the late varieties.6. When plants of different ages were grown in the high and cool region, the larger plants formed bulbs earlier than the smaller ones. The size of plant which was necessary to be attained before bulb formation, was larger in the late varieties than in the early ones.7. Those results show that the factors affecting bulb formation in onion are day-length, temperature and age of plant, of which temperature and age of plant are important for the early varieties, and photoperiod and age of plant are important for the late varieties.8. If photoperiod and age of plant were not sufficient for bulb formation of the variety, the tops did not fall down and remained erect. Long day and high temperature which promoted bulb formation, promoted topdown, too.

THE FORMATION OF LIGNIN IN WHEAT PLANTS

Wheat plants were harvested approximately every two weeks after emergence from the soil. Determination of the lignin content by the 72% sulphuric acid method showed a rapid increase between the period 45–70 days from seeding, and there was a corresponding increase in the yield of vanillin and syringaldehyde, obtained by alkaline nitrobenzene oxidation. The p-hydroxybenzaldehyde yield remained low at all times and seemed to be derived from a different system. It is suggested that the source of this aldehyde is not the lignin, but the tyrosine associated with the protein. The ratios of vanillin to syringaldehyde did not remain constant from plants of different ages, the percentage of syringaldehyde being lower than vanillin in the young plants and higher in those which were more mature. This is qualitatively in agreement with an increase in the methoxyl content of the lignin.When the yield of aldehydes from mature plants is taken as the criterion for the amount of lignin present, the youngest plants have a lignin content of about 0.13%, a value much lower than other bases for calculation would indicate.Oxidation of the whole plant and of the plant which had been extracted with alcohol–benzene, water, and 1% hydrochloric acid, gave similar percentages of aldehydes, owing partly to the removal of aldehyde-producing substances and partly to the degradation of the lignin during the extraction process. Oxidation of the extracts gave no trace of aldehyde in the hydrochloric acid extract, a trace in the water extract, and appreciable percentages in the alcohol–benzene extract. This latter extract consisted of two portions, a red water soluble, alcohol–benzene insoluble fraction and the main alcohol–benzene soluble fraction. The former gave rise to vanillin and p-hydroxybenzaldehyde on oxidation, the amount being a maximum at the first harvest and decreasing to zero after lignification had occurred. The latter, that is, the alcohol–benzene soluble extract, gave rise to syringaldehyde as well as the others, the amounts being low at first and increasing during lignification in the same way as the main body of the plant. It is believed that the alcohol–benzene removes a soluble portion of the lignin since the relative proportions of the aldehydes are very similar to those obtained from lignin itself.

Effectiveness of Photoperiodic Treatments of Plants of Different Age

Effectiveness of Photoperiodic Treatments of Plants of Different Age

INFLUENCE OF HOST FACTORS ON NEUROINVASIVENESS OF VESICULAR STOMATITIS VIRUS

INFLUENCE OF HOST FACTORS ON NEUROINVASIVENESS OF VESICULAR STOMATITIS VIRUS

On the Relation Between the Stage of Development of the Potato Crop and the Incidence of Blight (Phytophthora Infestans)

Summary.The evidence for the common opinion that potato plants above a certain age are on that, account more susceptible to blight than younger ones is based on (1) general field observations, (2) dates of planting experiments, (3) artificial inoculation experiments. The results of such observations and experiments are discussed and summarised, and it is shown that they do not consistently support this opinion; further, it is pointed out that much more careful analysis than is usually employed is needed to interpret the results correctly.The difference in behaviour towards blight sometimes observed between assemblages of old and young plants appears in reality to be due to variation in “epidemic potentiality,” and not to change in inherent susceptibility with age. It is not necessary to assume the existence of differences in susceptibility between plants of different ages, for the differences in disease intensity and resultant rate of spread will follow from the increasing chances of the occurrence of primary infection foci as the plants become older, and from the greater chances of the environment (particularly the micro‐climate) being suitable for the development of the parasite amongst older than amongst younger plants. Accurate conclusions concerning inherent resistance or susceptibility are possible only from carefully controlled artificial inoculation experiments carried out under uniform optimum infection conditions. Seedlings are often readily attacked so that youthfulness does not confer any degree of resistance on the plant. The results of experiments hitherto carried out with older plants are conflicting, and further study of the problem on carefully planned lines is eminently desirable.

DIFFERENCES IN RESISTANCE TO LOW TEMPERATURES SHOWN BY CLOVER VARIETIES

Differences shown by clover varieties in ability to withstand low temperatures are of great economic importance in the northern part of the United States. In this region the relative hardiness of a variety will often determine whether or not it is suitable for a given locality and whether or not it will endure average winter temperatures. The temperature limits for many crop plants can be determined best by field trials. Under field conditions, however, it is impossible to regulate or to control many conditions under which such tests are carried out and consequently the importance of a number of factors cannot be determined. Temperature is one of these factors. By mechanical control of temperatures it is possible to determine the response of varieties to different temperatures and the conditions under which the freezing of plant tissue occurs. The aim of this work was to determine if relative hardiness of clover varieties could be determined under conditions where temperature could be controlled. Tests were carried out at different stages of growth with a number of varieties of clover and a few varieties of alfalfa. Differences in exposure of plants were eliminated as far as possible by air circulation. Care was taken to obtain uniform conditions during periods of hardening and exposure to low temperature. The following points were considered in this group of tests: (1) Effect of low temperature on germination of clover seeds before planting; (2) Effect of low temperatures on the germination of seeds which had imbibed various amounts of water; (3) Effects of low temperatures on plants of different ages; (4) Differences in resistance to low temperatures shown by a number of varieties in the seedling and mature stages of growth.