Duration Of Vegetative Growth Research Articles

Phenological responses of maize to changes in environment when grown at different latitudes in China

Environmental conditions greatly affect the growth of maize. To examine differences in phenological responses of maize (Zea mays L.) to climatic factors under different environmental conditions as induced by latitude, experiments were conducted from 2007 to 2010 at 34 sites in seven Chinese provinces located in the north spring maize region of China between latitudes 35°11′ and 48°08′N in the cultivation of hybrid zhengdan958 (ZD958). Latitude is an important geographical factor which significantly affects temperature, sunshine hours, and the duration of crop growth. The findings of this study indicate that for every 1° increase in the latitude, northward, the growth durations of sowing to emergence and emergence to silking were significantly increased by 0.7 d and 1.25 d, respectively as a consequence of lowering temperatures (mean, maximum, and minimum temperatures). Reproductive growth duration (silking to maturity), which was significantly correlated with the precipitation, decreased by 0.8 d with each 1° increase in latitude northward. At higher latitudes, the number of growing degree days (GDD) of maize vegetative growth duration (emergence to silking) was significantly higher, and the GDD of the reproductive growth duration were significantly lower. The average photoperiod during the photoperiod-sensitive phase of maize development across all the experimental sites was 14.9h with a range of 13.7–15.6h. Total leaf numbers increased from 18.7 to 23.7 with an average of 21.0 across all experimental sites. Significant and positive linear relationships were found to occur between both latitude and photoperiods and latitude and total leaf number. In the north China spring maize region, the mean growth duration of ZD958 was 143.73 d, which constituted 82.8% of the frost free period, the percentage increasing with higher latitude. These findings strongly indicate that in order to ensure high and stable production of maize in the north spring maize region of China, with its limited heat resources, especially in the high-latitude regions, there is a need to cultivate short-growth-duration cultivars.

Optimization of traits to increasing barley grain yield using an artificial neural network

The grain yield (Y) of crops is determined by several Y components that reflect positive or negative effects. Conventionally, ordinary Y components are screened for the highest direct effect on Y. Increasing one component tends to be somewhat counterbalanced by a concomitant reduction in other component (s) due to competition for assimilates. Therefore, it has been suggested that components be manipulated in conjunction with other traits to break the competition-resulting barrier. The objective of this study is to optimize the effective components in conjunction with certain participant traits for increased barley Y using an artificial neural network (ANN) and a genetic algorithm (GA) as an alternative procedure. Two field experiments were carried out separately at the Agriculture Research Station located in Gonbade Kavous (37 o 16' N, 55 o 12' E and 37 asl), Iran. Ten genotypes were grown in each experiment, and the Y and certain traits/components were measured. Among the components/traits, those with a significant direct effect and/or correlation with Y were selected as effective for the ANN and GA analysis. The results indicate that the remobilization of stored pre-anthesis assimilates to grain (R1), crop height (R2), 1,000-grains weight (R3), grain number per ear (R4), vegetative growth duration (R5), grain-filling duration (R6), grain-filling rate (R7), and tiller number (R8) were effective. The R 2 for the training and test phases was 0.99 and 0.94, respectively, which reveals the capability of the ANN to predicting Y. The optimum values obtained by GA were 14.2%, 104.34 cm, 36.9 g, 41.9, 100 d, 48 d, 1.22 mg seed -1 day -1 , and 3.38 plant -1 for R1 through R8, respectively. The optimization increased the potential Y to 5791 kg ha -1 , which was higher than that observed for the genotypes (3527 to 5163 kg ha -1 ).

Photo-temperature response of ramie (Boehmeria nivea (L.) Gaud.) male sterile lines

Six male sterile lines (MSLs) of ramie (Boeh-meria nivea (L.) Gaud.) were grown in dark rooms under the photoperiods of 9.5h, 11h or 12.5h d-1 in spring and summer seasons (dif-ferent environmental temperatures) to test their developmental response to photoperiod and temperature. The MSLs showed little difference in vegetative growth duration, but different de-velopment rates in the reproductive growth stage under the tested conditions. Higher tem-perature (grown in summer) mainly accelerated vegetative growth, while the short photoperiod treatment accelerated the reproductive growth of the MSLs. Moreover, the short photoperiod treatment combined with higher temperature obviously accelerated both the vegetative and reproductive growth of the MSLs. But the effect of higher temperature decreased, or even dis-appeared along with the photoperiod elongation. The MSLs were divided into 5 photo-temperature response types, based on the flower budding acceleration of short pho-toperiod and the approximate temperature re-sponse index.

Assessment of genetic diversity of selected tartary and common buckwheat accessions

Genetic diversity of plant genetic resources for food and agriculture is a unique and irreplaceable source for further crop genetic improvement. The aim of this paper was the field evaluation of buckwheat genetic resources in the Czech Republic. In the case of the 77 common buckwheat (Fagopyrum esculentum Moench.) genotypes, most had reddishgreen stems (80%), cordate leaves (82%), white flowers (87%), and grey ovate achenes (44% and 57%, respectively). Vegetative growth duration ranged from 104 to 131 days. The 1000 seed weight (TSW) varied from 18.6 to 33.2 g. In the 15 tartary buckwheat (Fagopyrum tataricum Gaertn.) genotypes, there were no remarkable differences in morphological traits. Vegetative growth duration was 101 to 148 days, and the TSW varied from 8.10 to 20.0 g. Similarity/dissimilarity dendograms were calculated using the results of the field evaluation. Principal component analysis was also performed. The dendrograms showed high diversity in the morphological and phenological characteristics evaluated. Performance of the buckwheat varieties, particularly, their developmental stages, depended highly on the weather conditions of the year. Only days to flowering seemed to be affected by variety. Because the evaluation was made according to the IPGRI buckwheat descriptors the characteristics are compatible with data from other gene banks.

Performance of a High-Yielding Modern Rice Cultivar Takanari and Several Old and New Cultivars Grown with and without Chemical Fertilizer in a Submerged Paddy Field

A high nitrogen-uptake capacity and effective use of absorbed nitrogen for dry matter and grain production are required to improve the production cost and environmental pollution. We characterized grain yield, dry matter production and nitrogen accumulation in six rice cultivars: Sekitori (released in 1848) and Aikoku (1882), referred to as SA cultivars hereafter; Koshihikari (1956); Nipponbare (1963) and Asanohikari (1987), referred to as NA cultivars hereafter; and Takanari (in 1990) as a high-yielding modern cultivar. The plants were grown with and without chemical fertilizer in a submerged paddy field. When plants were supplied with manure and chemical fertilizer, Takanari consistently produced the heaviest grain and dry matter, followed by the NA cultivars, and the SA cultivars the lightest. Dry matter production before heading was greater in Takanari and the NA cultivars due to the longer duration of vegetative growth. Dry matter production after heading was greatest in Takanari, with a larger crop growth rate (CGR), and smallest in the SA cultivars with a shorter ripening time. Greater dry matter production during ripening was accompanied by the greater accumulation of nitrogen by Takanari and NA cultivars. These plants developed a larger amount of roots. The smaller light extinction coefficient of the canopy was also attributed to the higher CGR in Takanari. When plants were grown without chemical fertilizer, Takanari also produced heavier grain and dry matter, followed by the NA cultivars. The heavier grain in these cultivars resulted from the greater dry matter production before heading, which was due to the longer period of vegetative growth. The greater dry matter production and nitrogen accumulation by Takanari and NA cultivars were evident when plants were grown with chemical fertilizer. Koshihikari was characterized by a higher CGR and greater nitrogen accumulation during ripening in the absence of chemical fertilizer which should be noted in efforts to decrease rates of nitrogen application.

Effects of twice harvesting on total dry matter yield of rice

We examined the effect of twice harvesting of forage rice with the first harvest at the full heading stage on total dry matter yield in the cultivars Taporuri, Mohretsu, and Hinohikari and in line Saikaishi 253 in southwestern Japan. Taporuri produced the highest total dry matter yield, with a value 60% higher than that of Hinohikari. The first crop of Taporuri had a longer duration of vegetative growth than those of Mohretsu and Hinohikari, and had the highest dry matter yield because of its greater weight per tiller than Hinohikari and its more tillers per square meter than Saikaishi 253, which had a similar duration of vegetative growth. The second crops of Mohretsu, Taporuri, and Saikaishi 253 had longer vegetative growth and higher dry matter yields than Hinohikari. Dry matter yields of both crops were closely related to the duration of vegetative growth and the weight per tiller, but not to tillers per square meter. These results suggest that cultivars with a long duration of vegetative growth, high weight per tiller, and adequate tillers per square meter can produce high dry matter yield in both crops. There was a significant interaction ( P < 0.05) in total dry matter yield between cultivar or line and cultivation type. The total dry matter yield of Taporuri in twice harvesting was about 10% higher than that in once harvesting, whereas that of Hinohikari was about 10% lower. The suitability for twice harvesting ([total dry matter yield in twice harvesting]/[total dry matter yield in once harvesting]) was significantly positively correlated ( r = 0.875) with the increase in dry weight before the full heading stage, but significantly negatively correlated ( r = −0.903) with the increase in dry weight between full heading and the yellow ripe stage. Thus, cultivars with a high increase in dry weight before full heading appear to be more suitable for twice harvesting than those with a high increase between full heading and the yellow ripe stage. In addition, our study showed that twice harvesting can prevent lodging in Taporuri, thereby increasing the suitability of this cultivar as a forage rice. Our results suggest that twice harvesting can be performed in southwestern Japan and warmer regions.

Allocation of nitrogen to an inducible defense and seed production in Nicotiana attenuata.

Resource-based tradeoffs in the allocation of a limiting resource are commonly invoked to explain negative correlations between growth and defense in plants, but critical examinations of these tradeoffs are lacking. To rigorously quantify tradeoffs in a common currency, we grew Nicotiana attenuata plants in individual hydroponic chambers, induced nicotine production by treating roots with methyl jasmonate (MJ) and standardized leaf puncturing, and used 15N to determine whether nitrogen-based tradeoffs among nicotine production, growth, and seed production could be detected. Plants were treated with a range of MJ quantities (5, 45 or 250 μg plant-1) to effect a physiologically realistic range of changes in endogenous jasmonic acid levels and increases in nicotine production and accumulation; MJ treatments were applied to the roots to target JA-induced nicotine production, since nicotine biosynthesis is restricted to the roots. Leaf puncturing and 5 μg MJ treatments increased de novo nicotine synthesis and whole-plant (WP) nicotine pools by 93 and 66%, while 250 μg MJ treatments increased these values 3.1 and 2.5-fold. At these high rates of nicotine production, plants incorporated 5.7% of current nitrogen uptake and 6.0% of their WP nitrogen pools into nicotine. The 15N-labeled nicotine pools were stable or increased for the duration of vegetative growth, indicating that the N-nicotine was not metabolized and re-used for growth. Plants with elevated nicotine production grew more slowly and the differences in plant biomass gain between MJ-treated plants and controls were linearly related to the differences in nicotine accumulation. Despite the reductions in rosette-stage growth associated with nicotine production, estimates of lifetime fitness (cumulative lifetime seed production, mass/seed, seed viability) were not affected by any treatment. Only two treatments (leaf puncturing and 250 μg MJ) increased the allocations of 15N acquired at the time of induction to seed production. On average, plants used only 14.9% of their WP nitrogen pool for seed production, indicating that either the nitrogen requirements for seed production or the reproductive effort of these hydroponically-grown plants are low. To determine if seed production is strongly influenced by the amount of vegetative biomass attained before reproduction, the experiment was repeated with plants that had 44% of their leaf area (or 29% of their WP biomass) removed before MJ treatments with a removal technique that minimized the nicotine response. MJ treatments of these plants dramatically increased nicotine production and accumulation, but these plants also suffered no measurable fitness consequences from either the leaf removal or MJ treatments. We conclude that when N. attenuata plants are grown in these individual hydroponic chambers, their allocation to reproduction is sufficiently buffered to obscure the large increases in nitrogen allocations to an inducible defense. To determine whether soil-grown plants are similarly buffered, we grew two genotypes of plants in the high-nutrient soil from a 1-year-old burn in a piñyon-juniper forest (the plants' natural habitat) and in low-nutrient soil from an adjacent unburned area, and induced nicotine production in half of the plants with a 500 μg root MJ treatment. Plants grown in burned soils had an estimated lifetime fitness that was on average 2.8-fold greater than that of plants grown in unburned soils. MJ treatment reduced fitness estimates by 43% and 71% in the burned and unburned soils, respectively. We conclude that while hydroponic culture allows one to rigorously quantitate nitrogen allocation to growth, reproduction and defense, the allocation patterns of plants grown in hydroponic culture differ from those of plants grown in soil. Under hydroponic conditions, plants have low reproductive allocations and reproductive-defense tradeoffs are not detected. Reproductive-defense tradeoffs are readily discernible in soil-grown plants, but under these growing conditions, the nitrogen-basis for the tradeoff is difficult to quantify.

Leaf Appearance Rate and Final Leaf Number of Switchgrass Cultivars

In switchgrass (Panicum virgatum L.), maximum yields occur with late flowering genotypes that have an extended duration of vegetative growth. However, little is known about the developmental basis for a long vegetative growth phase in perennial grasses. Studies were carried out on the leaf development of five switchgrass cultivars with varying flowering times (Cave‐in‐Rock, Caddo, Kanlow, NC2, and Alamo) to provide inputs for crop simulation models and to determine if a long duration of vegetative growth was associated with a reduced rate of leaf appearance or a high final leaf number. The studies were carried out in the field at College Station, TX, (30°38'N, 96°20'W), during 1994 and 1995. Thirty tillers emerging in spring were tagged and visible leaves were recorded weekly until panicles emerged. Final leaf numbers were recorded on the flowering tillers which had emerged in spring and after a June defoliation. Tillers of all cultivars emerged in March and panicles emerged during a 2‐too period from May to July. Final leaf number of spring‐emerging tillers of all cultivars ranged from nine to 11, whereas summer‐emerging tillers flowered after seven leaves had appeared. The phyllochron [growing degree days (GDD) between the appearance of two successive leaves] for all cultivars increased with advancing leaf number. High average phyllochron values (GDD base 10°C) were associated with late panicle emergence and a long duration of vegetative growth. Cave‐in‐Rock, the earliest flowering cultivar, averaged 79 GDD per leaf and required 634 GDD to attain panicle emergence, while Alamo, the latest to flower, averaged 152 GDD per leaf and required 1777 GDD to attain panicle emergence. A slow rate of leaf appearance was identified as the primary developmental trait associated with a long duration of vegetative growth in switchgrass.

Climatic Constraints on Rice Production in Taiwan

Two crops of rice can be cultured each year in Taiwan. The yield of the second rice crop is, on average, 25% lower than that of the first crop. Climatic constraints such as extreme temperatures, lower solar radiation, monsoons, and heavy rainfall, are the main factors causing the yield loss. Chilling injury at the seedling nursery stage and prolonged mei-yu at the reproductive stage frequently impair the growth and development of the first rice crop and hence influence yield performance. For the second rice crop, high temperatures during the early growth phase of the rice plants shortens the vegetative growth duration and consequently results in lower tiller numbers and biomass production. The occurrence of typhoons and the associated heavy rainfall can also cause significant damage to the crop. In addition, low temperature and low solar radiation after heading adversely affect the performance of seed-settling and 1, 000-grain weight, especially in the central and northern parts of Taiwan. For improvement, it is suggested new cultivars suitable for growth under the stress conditions be developed, and the cultural practices be improved to overcome the impacts caused by unfavorable climatic constraints.

Variation in Rate and Duration of Growth Among Spring Barley Cultivars1

AbstractTen two‐rowed spring barley cultivars (Hordeum vulgare L.) were evaluated for growth parameters, i.e. crop growth rate, crop growth duration, grain filling rate, grain filling duration, vegetative growth rate, vegetative growth duration, single caryopsis filling rate, single caryopsis filling duration. Field studies were conducted on a sandy loam at Hohenschulen, Northern Germany with three levels of nitrogen fertilization and three sowing rates in 1986 to 1988. Cultivar effects were observed for all growth parameters except for crop growth rate and vegetative growth rate. But only crop growth duration n and grain filling duration showed positive correlations with grain yield. No growth rate parameter was related to yield. Biomass was correlated to crop growth duration and not to crop growth rate, while average caryopsis weight was strongly related to caryopsis filling rate and only moderately to caryopsis filling duration. Comparing grain filling rate and duration to individual caryopsis filling rate and duration, only grain filling rate and duration appeared to be relevant to grain yield. Since genetic variability for crop growth rate was lacking in the spring barley material tested, further improvement of yield would only result from increase in harvest index and/or longer crop growth duration.

Heterochronic Effects of Teopod 2 on the Growth and Photosensitivity of the Maize Shoot.

Teopod 2 (Tp2) is a semidominant mutation of maize that prolongs the expression of juvenile vegetative traits, increases the total number of leaves produced by the shoot, and transforms reproductive structures into vegetative ones. Here, we show that Tp2 prolongs the duration of vegetative growth without prolonging the overall duration of shoot growth. Mutant shoots produce leaves at the same rate as wild-type plants and continue to produce leaves after wild-type plants have initiated a tassel. Although Tp2/+ plants initiate a tassel later than their wild-type siblings, this mutant tassel ceases differentiation at the same time as, or shortly before, the primary meristem of a wild-type tassel completes its development. To investigate the relationship between the vegetative and reproductive development of the shoot, Tp2/+ and wild-type plants were exposed to floral inductive short day (SD) treatments at various stages of shoot growth. Tassel initiation in wild-type plants (which normally produced 18 to 19 leaves) was maximally sensitive to SD between plastochrons 15 and 16, whereas tassel branching was maximally sensitive to SD between plastochrons 15 and 18. Tassel initiation and tassel morphology in Tp2/+ plants (which normally produced 21 to 26 leaves) were both maximally sensitive to SD between plastochrons 15 and 18. Thus, the constitutive expression of a juvenile vegetative program in Tp2/+ plants does not significantly delay the reproductive maturation of the shoot.

Effects of Rootstock and Nitrogen Fertilization on the Growth and Yield of Chardonnay Grapevines in New York

Two rootstocks and three nitrogen fertilizer rates were evaluated for their effects on growth, yield, and petiole nutrient concentrations of Chardonnay (<i>Vitis vinifera</i> L.) grapevines. Rootstock had a greater effect on scion growth than did differential N application (0, 39, or 84 kg N/ha/yr), even though increased N availability significantly increased petiole N concentrations in the second year of application. Cane pruning weights of vines grafted to Couderc 3309 (C-3309) rootstocks averaged 1.42 and 1.20 kg/vine in 1984 and 1985, respectively. Pruning weights of vines grafted to Elvira averaged 0.75 and 0.79 kg, respectively, in those years. Fruit yields were not proportional to vine size; yields averaged 4.55 and 4.45 kg per vine in 1984 and 1985, respectively, with vines grafted to C-3309 and 4.08 and 4.13 kg per vine, respectively, for vines grafted to Elvira. Increased N availability reduced yields with vines grafted to C-3309 and increased yields in one year with vines grafted to Elvira. The percentage of flowers that set fully developed berries in 1985 was greater for vines grafted to Elvira than for vines grafted to C-3309. Fruit set of non-fertilized vines grafted to C-3309 was greater than fruit set of vines that received 84 kg N/ha. In addition to effects on growth and fruit set, vines grafted to C-3309 were associated with greater shoot growth rates, greater petiole potassium concentrations, and denser canopies than were vines grafted to Elvira. Neither rootstock nor applied N affected the duration of vegetative growth.

RELATIONSHIPS OF VEGETATIVE GROWTH AND PEPPER YIELD

Fruit yields, root dry weights, and total plant dry weights of Keystone Resistant Giant and Ladybell bell peppers (Capsicum annuum L.) increased linearly as the duration of vegetative growth was extended by defloration. The fruit:total dry weight ratio increased, while the root:total dry weight ratio remained the same; the shoot:total and leaf:total ratios decreased as duration of vegetative growth increased.Key words: Pepper, defloration, flower bud abscission, vegetative, reproductive growth, Capsicum annuum L.

Influence of Vegetative Growth Duration on Grain Grade

Influence of Vegetative Growth Duration on Grain Grade

Shoot demography and morphology of Zostera japonica and Ruppia maritima from British Columbia, Canada

Shoot dynamics and morphology were studied in co-occuring intertidal populations of Zostera japonica Aschers. and Graebn. and Ruppia maritima L. s.l. in southwestern British Columbia. Repeated mapping and examination of cohorts of shoots (ramets) in permanent plots on a gradient in elevation showed that the appearance and loss of shoots, age structure, survivorship and leaf and rhizome dimensions were all affected by position on the gradient. For both species, the area having the greatest exposure t o air had fewer shoots and a greater percentage of shoots flowering early in the season. The duration of vegetative growth in R. maritima was the same regardless of elevation, while plants of Z. japonica at high elevation initiated and ended flowering and entered a quiescent overwintering state earlier than plants at lower elevation.

Effects of Photoperiod and Temperatures on the Duration of Vegetative Growth in Maize1

One objective of this study was to identify parental genotypes to be used in subsequent research into the inheritance of sensitivity to photoperiod in maize (Zea mays L.). Seventy inbreds were surveyed for their maturity responses under two photoperiods in a phytotron greenhouse. For short‐day maturity, a range was observed from 10.0 leaves for C3 to 23.0 leaves for Tx601. For photosensitivity (difference between long‐day and short‐day maturity), the range extended from 0.0 leaves for B14A to 8.5 leaves for CM103. The correlation between short‐day maturity, and photosensitivity across all entries was significantly positive, but among inbreds exhibiting moderate or late short day maturity, a large range in photosensitivity occurred. The maturity responses of seven inbreds were further examined in growth chambers primarily to study photoperiod ✕ temperature interactions and to compare two measures of maturity in maize. Based on days to tassel initiation (DTI) and particularly total leaf number (TLN), the effect of photoperiod was considerably greater than that of temperature. Photoperiod ✕ temperature interactions were significant only for DTI. Total leaf number (TLN) was concluded to be better than DTI for measuring effects of photoperiod upon the duration of vegetative growth in maize. Several other results with important implications for subsequent research on the inheritance of photosensitivity in maize are discussed.

Performance of Near‐Isogenic Genotypes of Rice Differing in Growth Duration. II. Carbohydrate Partitioning During Grain Filling1

The distribution of non‐structural carbohydrates during grain filling was compared for a near‐isogenic pair of rice (Oryza sativa L.) genotypes that differed by 18 days in their vegetative growth duration. The objective was to determine the effect of the longer vegetative growth period on the production of assimilates that would later be remobillzed and used in grain filling. The percentage of total sugars in all measured vegetative plant parts declined after 17 days of grain filling of EDT, the earlier genotype. Sugar percentages did not decline from heading to full maturity for ‘Calrose 76,’ the later genotype. Starch percentage at the start of grain filling was greater for Calrose 76 than for EDT. At maturity, Calrose 76 had 33.6, 12.5, and 2.3% starch, respectively, in the third internode, second internode and sheath, and first internode and sheath. At maturity, ED7 was essentially devoid of starch in these same plant parts. Calrose 76 also used some of the vegetatively stored starch during grain filling. The apparent contribution of preheading stored nonstructural carbohydrates to grain filling of the two genotypes was about the same for the early sown (11 May) comparison. The same comparison for the later sown (21 May) trial showed ED7 with 15.6% and Calrose 76 only 6% apparent contribution to grain filling. Increased rates of N fertilizer enhanced the apparent contribution to grain filling of both genotypes sown early but not for the later sown trial. Daily rates of starch accumulation in the panicles averaged for the two genotypes began to decline by the 17th day after heading. The daily rates of sugar accumulation were nearly the reciprocal of daily rates of starch accumulation in the panicle. In an environment of full sun and warm days during grain filling, cultivars with longer growth periods probably can support larger panicles than those with shorter growth periods.

Monogenic Control of Basic Vegetative Phase and Photoperiod-sensitive Phase in Rice

Lm which belongs to the linkage group I is one of the primary loci controlling heading time of cultivated rice and is also associated with photoperiod sensitivity. The effects of alleles of the Lm locus on two phases of the vegetative growth duration, the basic vegetative phase and the photoperiod-sensitive phase, were analysed by growing two isogenic lines with Lme and Lmu allelles under natural and controlled daylengths. Heterozygotes (Lme/Lmu) were maintained during 15 generations Lrom F1 through BC4F11 in the cross between the Malaysian cultivar Morak Sepilai and the Japanese cultivar Fujisaka 5, which was used as the recurrent parent for the successive four backcrosses. Fujisaka 5 and Morak Sepilai transmitted the early-maturing allele Lme and the late-maturing allele Lmu to their hybrid progenies, respectively.

Results of Varying the Date of Seeding and Altering the Spacing of Stands on the Growth of Ears in Spring Oats

Experiments were conducted on the effects of varying the date of seeding and altering. the space of individual plants on the growth of the ear and the tiller in spring oats. A spring oats variety, Kairyo-Hadaka was sown at four various seeding rates, i.e. 0.8, 0, 5, 0.2 and 0.08 bushels per acre in rows 2 ft apart, and at five different dates from April 27 to June 22 with 2 week intervals in 1953. Weekly measurements were made on the growth i.e. rate of increase in leaf number and of elongation in culm height and panicle length. Culm height and panicle length at the stage of panicle differentiation were measured by peeling the leaves. From the results it was noted that the number of tiller increased from only one in the plots of highest density of stands to about 15 in the lowest, throughout every date of seeding. The number of leaves and the height of main culm were found not to relate to the date of seeding but to the rate of it. The rate of increase of leaf number in older tillers was found slightly lower as the tiller was younger, but those bearing only three leaves or less did not produce ears though such tillers in spring wheat plants do. Furthermore, the duration of vegetative growth was consistently about 7 weeks in every seeding date. The vegetative growth of this oats variety seemed not to be affected by environmental factors, such as day length or air temperature.

Measuring Soil Temperature by Standard Thermometer Suspended in Iron Pipe

Soil temperature affects not only the functional activity of tree roots, but also the rate and duration of vegetative growth. The differences in the vegetation of north and south slopes which are particularly evident in the more extreme climatic conditions of many parts of the West are largely the result of variations in soil temperature. The rapid increase in the development of reproduction which usually occurs after the removal of an overwood may be to a considerable degree the result of increased soil temperature. This is true particularly of species near the northern limit of their range. The temperature of the upper layers of the soil fluctuates more or less in harmony with atmospheric changes; with increasing depth the peaks and depressions disappear and a progressive smoothing of the curve takes place. The daily range at a depth of 2 feet rarely exceeds 1? F. and is inappreciable below three feet. Seasonal variations penetrate to much greater depth. The measurement of these changes is a necessary part of the study of the habitat, and is a field of investigation which has been overshadowed in the past by more obvious lines of research. Soil temperatures at varying depths are usually measured by means of the so-called standard soil thermometers, which are expensive and subject to breakage. In recent years many investigators have measured soil temperatures by means of the ordinary standard thermometer lowered to the required depth within an iron pipe driven into the soil, and projecting six inches or more above the surface. In some instances where the temperature is taken at less than two feet in depth a wooden pipe is used, as it affords better insulation. In investigations during recent years at the Yale School of Forestry iron pipes have been inserted at varying depths in the soil, projecting six inches above the surface. Two years ago (extending over a period of two months) comparative readings were taken, from standard soil thermometers and from standard thermometers in iron pipes at depths of six inches, one foot, two feet, and three feet. These investigations showed that with the pipes extending six inches above the soil the variations in readings between the two sets of thermometers at two feet or more in depth rarely exceeded Y20 F. and usually were much less. At less depths, however, the difference in the read-