Grafted Apple Trees Research Articles

Isolation of Trichoderma virens 6PS-2 and its effects on Fusarium proliferatum f. sp. Malus domestica MR5 related to apple replant disease in China

Apple replant disease (ARD) is primarily caused by biotic factors that seriously inhibits the development of apple industry. Therefore, the use of biological control measures to inhibit the main pathogens (such as Fusarium spp.) that cause ARD is of great significance to the sustainable development of the apple industry. Trichoderma virens 6PS-2, which exhibited antagonism toward a variety of pathogens, was screened from the rhizosphere soils of healthy apple trees (Malusrobusta) in different replanted orchards in the Yantai and Zibo Cities, Shandong Province, China. Its fermentation extract inhibited the growth of pathogenic Fusarium proliferatum f. sp. Malus domestica MR5, which was proportional to the concentration. These substances also increased the hairy root volume and growth of Arabidopsis thaliana lateral roots. The phenotype of Malus hupehensis seedlings and microbial community structure in rhizosphere soils in greenhouse experiment using High-throughput sequencing were analyzed, and the field experiment with grafted apple trees were used for further verification. Compared with the application of potato dextrose broth (PDB) medium, application of 6PS-2 spore suspension directly to replanted soils could improve the growth of M. hupehensis seedlings as well as the elongation of grafted apple trees. Concomitant decreases in the gene copy number of Fusarium and increases in the culturable bacteria/fungi were also observed in the greenhouse and field experiments. The abundance of Trichoderma, Bacillus, and Streptomyces increased significantly, but that of Fusarium, Pseudarthrobacter, and Humicola decreased. The content of esters, phenols, furans, and amino acids in root exudates of M. hupehensis seedlings increased, which significantly inhibited the multiplication of Fusarium, but was positively correlated with Bacillus and Trichoderma. In summary, T. virens 6PS-2 not only directly inhibits the activity of pathogenic Fusarium but also secrets secondary metabolites with antifungal and growth-promoting potential. In addition, 6PS-2 spore suspension can also promote the growth of plants to a certain extent, and change the soil microbial community structure of rhizosphere soils. It is believed that T. virens 6PS-2 has the potential for the alleviation of apple replant disease (ARD) in China.

Remote estimation of grafted apple tree trunk diameter in modern orchard with RGB and point cloud based on SOLOv2

Apple tree phenotyping can reflect individual development of single apple tree, which mainly involves tree height, crown width, and diameter of apple tree trunk (DATT). This study aimed to estimate diameter of grafted apple tree trunk, whose target position of diameter estimation is about 10 cm above grafting position. An estimated DATT approach of combining red–greenblue-depth (RGB-D) sensor with SOLOv2 was proposed. Firstly, Kinect V2 was employed to obtain original RGB images and point clouds of the grafted apple trees simultaneously. There were 120 and 60 RGB images and corresponding point clouds randomly collected from two modern apple orchards. Secondly, SOLOv2 deep learning model was selected and trained to instance segment grafting position from RGB image for determining it automatically. Then, corresponding exact position of the grafting position in point cloud was mapped by coordinate transformation of its pixel coordinates, which was obtained by trained SOLOv2 model. Finally, DATT was estimated by calculating the difference between maximum and minimum Y coordinates of points selected by distance thresholds in X, Y, and Z directions near the target position, which were 0.10 m, 0.035 m, and 0.20 m, respectively. Results showed that average precision and average recall of the trained SOLOv2 model for instant segmenting the grafting position were 0.811 and 0.830, respectively. Mean absolute error, mean absolute percentage error, and root mean square error of the proposed method were 3.01 mm, 5.86%, and 3.79 mm, respectively. It illustrates that the proposed method can estimate DATT and thus contribute to automatic apple tree phenotyping.

The nutrient, hormone, and antioxidant status of scion affects the rootstock activity in apple

In grafted plants, rootstock growth and stress resistance are influenced by scion traits, but the underlying mechanism is unclear in apple. In this study, we analyzed seedlings comprising wild-type (WT) or increased-branching mutant (MB) scions on Malus robusta rootstock on the basis of RNA-seq data, physiological and biochemical indices, and gene expression. Gene functional analysis of RNA-seq data revealed plant–pathogen interaction was the most significantly enriched biological pathway in the axillary buds and roots compared MB with WT. Most genes related to stress responses had up-regulated expression in the MB roots. The leaf water potential, chlorophyll content, and photochemical efficiency were lower in the MB leaves, whereas the water loss rate was higher. The sucrose, glucose, fructose, and sorbitol contents increased significantly in the MB leaves, but decreased in the stems. In the MB roots, there was no change in sucrose and glucose contents, but the fructose and sorbitol contents increased and decreased, respectively. The nitrogen, phosphorus, and potassium contents were higher in the MB roots, while lower nitrogen and phosphorus and higher potassium contents in MB leaves. The abscisic acid, malondialdehyde, and hydrogen peroxide levels increased significantly in the MB seedlings, whereas the antioxidant enzyme activities decreased, especially in the roots and leaves, which was in accordance with the down-regulated expression of the genes related to antioxidant enzyme synthesis. These changes in the MB roots were apparently due to MB scion traits, suggesting that rootstock vitality in grafted apple trees may be affected by the nutrient distribution, hormone level, and antioxidative stress tolerance of the scion.

Foliar and root uptake of N deriving from simulated atmospheric N depositions in potted apple (Malus domestica) trees

A significant human-driven increment of the available reactive nitrogen (Nr) forms has occurred during the past century at the global scale, which in turn has increased the amount of Nr deposition. Grafted apple trees (Gala / M.9 strain T337) were used in a pot experiment conducted in semicontrolled conditions, where the 15N-labelling technique allowed to trace the fate of N from ammonium nitrate (15NH4 15NO3, isotopic enrichment: 10.3 atoms %) distributed at three increasing rates (N1, N2, N4, where N2 is the double of N1 and N4 is the double of N2) either to soil or to canopy (foliar application) to simulate atmospheric N depositions. At the end of the experiment, plants were destructively sampled, and N derived from depositions (Ndfd), total N, and biomass of above and belowground organs were determined. Uptake rates ranged from 21% to 57% and the Ndfd recovery was higher for soil than for foliar application. Foliar-supplied plants showed a higher Ndfd in leaves and shoots than soil-supplied ones, while the latter showed a higher Ndfd in roots than the former. Moreover, total N in trunk, shoot axes and leaves increased with the N rates up to the level N2, with no further increase in N4. Increasing tree N availability, regardless the supply mode, increased the shoot:root N content. The fact that the N uptake rate was rather stable at increasing N rates suggests that if N from atmospheric depositions becomes increasingly available at the canopy or soil level, it will actively contribute to apple tree nutrition and account for a significant fraction of the apple tree N needs.

Morphological and photosynthetic responses differ among eight apple scion-rootstock combinations

‘Red Fuji’ apple (Malus × domestica Borkh.) scions were grafted onto eight size-controlling rootstock combinations (dwarfing, semi-dwarfing, and vigorous types). During the third year after grafting, morphological and physiological parameters, such as growth, hydraulic conductance, non-structural carbohydrates, gas exchange and chlorophyll fluorescence, as well as leaf anatomy, were examined and instantaneous whole-canopy photosynthetic assimilation was modelled. Compared with Baleng, rootstocks M.9 and B.9 resulted in reduced growth vigour and photosynthetic capacity. Significantly lower soil-to-leaf hydraulic conductance, stomatal density and palisade/spongy parenchyma ratios were also observed in ‘Red Fuji’ grafted on M.9 and B.9. We propose that the down-regulated hydraulic conductance contributed to the decline in photosynthetic rate, which in turn caused a reduction in instantaneous whole-canopy photosynthetic assimilation. These results provide evidence that the limited photosynthetic capacity and leaf area are major causes of the reduced canopy photosynthetic assimilation observed in M.9 and B.9 grafted apple trees. The reduced photosynthetic assimilation may partly result from a sustained lower photochemical efficiency. However, dwarfing and semi-dwarfing rootstocks grafted plants contained more starch, which may be a significant factor underlying the observed advanced precocity.

Physiological responses of four apple (Malus × domesticaBorkh.) rootstock genotypes to soil water deficits

The use of drought-tolerant rootstocks is an important strategy in maintaining orchard productivity while meeting the increasing need to conserve water resources. The drought tolerance of two new genotypes, Vineland 1 (V.1) and Vineland 3 (V.3), was assessed along with industry standards to test the hypothesis that differences in water-use efficiency exist among these apple rootstocks. One-year-old, non-grafted nursery liners of M.9, MM.111, V.1, and V.3 were grown in a controlled-environment experiment. Plants of each genotype were maintained water-replete or were subjected to a 9-d controlled dry down and then maintained under water stress conditions for 55 d. Water stress reduced biomass accumulation and trunk cross-sectional area for all four genotypes. The two vigorous genotypes, MM.111 and V.1, increased their root-to-shoot ratios in response to water stress, whereas the root-to-shoot ratios of M.9 and V.3 remained unchanged in their water-replete controls. Genotype V.3 maintained its transpiration at a significantly lower soil water content compared to M.9, MM.111, and V.1. Of the four genotypes, V.3 demonstrated a high tolerance to water stress conditions, and therefore deserves further investigation using grafted apple trees in an orchard study.

Biological effects of ion beam irradiation on perennial gentian and apple.

The development of new varieties of perennial plants generally requires lengthy and laborious procedures. In this study, we used ion beam irradiation mutagenesis in an attempt to accelerate the breeding process for perennial plants. We evaluated the biological effects of five ion beam sources (carbon, neon, argon, silicon, and iron) and neutron irradiation on Japanese gentian and apple. These treatments were applied at the National Institute of Radiological Sciences (NIRS) using the Heavy Ion Medical Accelerator in Chiba (HIMAC) and the Neutron-exposure Accelerator System for Biological Effect Experiments (NASBEE). Biological effects were observed in in vitro gentian plants after irradiation with ion beams at <10 Gy, whereas apple trees were less sensitive to ion beam irradiation. The growth of gentians in vitro was repressed by 3 Gy neutron irradiation, while that of grafted apple trees was not affected by 4 Gy neutron irradiation. During in vitro proliferation, seven pink-flowered lines were obtained from originally blue-flowered gentian after C and Ne ion beam irradiation treatments. Genomic and reverse transcription-PCR analyses of these lines suggested that the mutations occurred in the genomic region containing F3'5'H (encoding flavonoid 3',5'-hydroxylase). These results provide useful information for the mutagenesis and breeding of gentian, apple, and other perennial plants.

Nursery tree design modifies annual dry matter production of newly grafted ‘Royal Gala’ apple trees

Total annual dry matter production of apple trees is correlated with the total amount of solar radiation intercepted by their leaf canopy. This fundamental principle has application in maximising the seasonal growth, size and quality of newly propagated apple trees. In this study, we grafted ‘Royal Gala’ scions (Malus×domestica Borkh.) onto one-year-old rootstock stools of ‘Malling 9’ (‘M9’) in winter, and grew trees in the subsequent spring with either one (monoaxis) or two (biaxis) primary axes per tree, to compare how each nursery tree design modified leaf area development, dry matter production and floral precocity. From 20 days after spring budbreak onward, biaxis trees had produced significantly more dry weight of leaf, scion and whole tree. For the first 120 days of growth, the period where no sylleptic shoots were present for either treatment, the total leaf area and dry weight of biaxis trees were greater than those of monoaxis trees, and trees that had a greater total leaf area also had a greater total tree dry weight. By growth cessation in late autumn, the final dry weight of tree was 35% higher for biaxis than for monoaxis trees, with biaxis trees showing greater dry weight gain in both the root system and scion. In the following spring, biaxis trees had a higher percentage of buds (15%) that were floral than monoaxis trees. We conclude that early-season leaf area development, which is necessary for light interception and photosynthesis, is an important factor limiting dry matter accumulation of newly grafted apple trees. The greater final biomass present in both root and scion of one-year-old biaxis nursery trees may contribute to accelerated canopy development of the planted orchard, while their greater flowering intensity indicates high potential for early cropping.

Optimizing planting density for production of high-quality apple nursery stock in China

In China, apple (Malus × domestica Borkh.) nursery stock is generally of low quality because of extremely high planting density. The objective of this study was to determine the optimum planting density of 2-year-old grafted apple trees. Tree growth (height, trunk diameter, leaf area index) increased as density decreased. Trees grown at high densities (14.3–50 plants/m2) were the shortest with the smallest trunk diameters and leaf areas, whereas trees grown at lower densities (4.8–10 plants/m2) were generally largest in terms of height, diameter and leaf area. Trees grown at lower densities tended to have higher bud dry weight, leaf dry weight, nitrogen content, total soluble sugar concentration and total non-structural carbohydrate content. Higher levels of these parameters were generally observed with tree densities at or below 10 plants/m2. Therefore we conclude that 10 plants/m2 is the optimum density for maximizing the number of trees produced per unit land area while maintaining tree quality of nursery stock.

Shifts in xylem vessel diameter and embolisms in grafted apple trees of differing rootstock growth potential in response to drought

We investigated responses of plant growth rate, hydraulic resistance, and xylem cavitation in scion-rootstock-combinations of Malus domestica L. cv. Honeycrisp scions grafted onto a high-shoot vigor (HSV) rootstock, (semi-dwarfing Malling111), or onto a low-shoot vigor (LSV) rootstock, (dwarfing Budagovsky 9), in response to substrate moisture limitation. Adjustments in xylem vessel diameter and frequency were related to hydraulic resistance measurements for high- versus low- vigor apple trees. We observed a greater tolerance to water deficit in the high-shoot compared to the low-shoot vigor plants under water deficit as evidenced by increased growth in several plant organs, and greater scion anatomical response to limited water availability with ca. 25% increased vessel frequency and ca. 28% narrower current season xylem ring width. Whereas water limitation resulted in greater graft union hydraulic resistance of high-shoot vigor trees, the opposite was true when water was not limiting. The graft union of the low-shoot vigor rootstock exhibited higher hydraulic resistance under well-watered conditions. Scions of high-shoot vigor rootstocks had fewer embolisms at low plant water status compared to scions of low-shoot vigor rootstocks, presumably as a result of large differences in xylem vessel diameter. Our results demonstrated that anatomical differences were related to shifts in hydraulic conductivity and cavitation events, a direct result of grafting, under limited soil water.

Origins of Pioneer Apple Orchards in the American West: Random Seeding versus Artisan Horticulture

Abstract Before the Revolution, colonial American consumers reconstituted the English apple orchard. Unremarkable random seedling apples and "high" flavored English cider fruits were devalued. Late colonial consumers selected a range of sweeter, more versatile apples for fresh use and culinary preparations, others for drying, and many "winter keepers" for long-term storage. These trees were supplied by distinctive, horticulturally trained farmers who produced grafted trees as part of their mixed crop output. Demand for this first catalog of American apple trees exploded in the Ohio Valley, where surging farm establishment fueled commercial agricultural enterprises. By 1800 pioneer artisan horticulturists were selling America’s favorite cultivated apple tree varieties to frontier farmers while mythologized peddlers of unimproved, random seedlings contributed only marginally. By 1820 craft nurserymen marketed tens of thousands of grafted apple trees annually and were among the most commercially oriented farmers in the Old Northwest.

Origins of Pioneer Apple Orchards in the American West: Random Seeding versus Artisan Horticulture

Before the Revolution, colonial American consumers reconstituted the English apple orchard. Unremarkable random seedling apples and high flavored English cider fruits were devalued. Late colonial consumers selected a range of sweeter, more versatile apples for fresh use and culinary preparations, others for drying, and many winter keepers for long-term storage. These trees were supplied by distinctive, horticulturally trained farmers who produced grafted trees as part of their mixed crop output. Demand for this first catalog of American apple trees exploded in the Ohio Valley, where surging farm establishment fueled commercial agricultural enterprises. By 1800 pioneer artisan horticulturists were selling America's favorite cultivated apple tree varieties to frontier farmers while mythologized peddlers of unimproved, random seedlings contributed only marginally. By 1820 craft nurserymen marketed tens of thousands of grafted apple trees annually and were among the most commercially oriented farmers in the Old Northwest.

EFFECT OF INORGANIC FERTILIZER, MYCORRHIZA AND FARM YARD MANURE ON GROWTH OF MICROPROPAGATED APPLE ROOTSTOCK M.7, FOR THE PRODUCTION OF GRAFTABLE PLANTS IN ONE YEAR

Micropropagation in comparison with the vegetative propagation methods, helps to increase the production in shorter periods of time. But, in case of micropropagated apple rootstocks it still takes 2 years for the plants to attain a thickness appropriate for grafting. In this context it was aimed to evaluate the effect of inorganic fertilizer, mycorrhiza (AM, Glomus intraradices) and farmyard manure (FYM) on growth of micropropagated apple rootstock M.7. Plants acclimatized for one month were transplanted into pots and were maintained in nursery for 6 months. Eight treatments tested include: soil (control); soil + AM; soil + FYM (4:1v/v); soil + N-P-K; soil + N-P-K + AM; soil + FYM + AM; soil + FYM+ N-P-K and soil + FYM + NPK+AM. N-P-K fertigation was done 8 times at an interval of 14 days using 0.2% 19-19-19 N-P-K fertilizer. The variables analyzed involve survival percentage, shoot height, number of leaves, number of new leaves, percentage root colonization, root length, plant biomass. Root colonization was observed in all the treatments and was not effected by addition of FYM and NPK. Nevertheless, AM fungi had no significant effect on growth in any of the treatments. Soil + FYM + NPK and soil + FYM + NPK + AM out of eight treatments, enhanced shoot height (4 fold), number of leaves (2 fold) and plant biomass significantly as compared to the control. None of the treatments had a significant effect on survival percentage, root length and emergence of new leaves. Considering that 100% of plants treated with these two treatments attained graftable thickness in 6 months as against 8% plants in the control, it can be successfully applied for the production of grafted apple trees in lesser time.

PLANTING STOCK QUALITY ACCORDING TO THE METHOD OF APPLE TREE CROWN FORMATION IN THE FRUIT NURSERY

One of the main factors of modern orchard foundation, including that of apple trees, is the superior quality of the planting material: superior genetically (clonal), phytosanitary healthy (virus free), physiologically well-developed (licensed). These superior qualities of the planting material contribute to an early entering of fruit trees on fructification and an increase of the plantation’s productivity with about 20-25 % than the ordinary one. At present in the superintensive apple tree orchard from the Republic of Moldova there are planted grafted apple trees on the rootstock M 9 having the form of rods without ramifications. The crown formation is made after the plantation of the apple trees in the orchard according to actual recommendations. From the experience of the countries with a developed pomology, the superintensive apple trees orchards are planted with trees produced during 2 years with a formed crown of “knip baum” type. The researches were made during the period of 2005-2007 in the fruit nursery of the firm “Fruit Nurseries” Ltd. As a rootstock was used the M 9 type and as a graft – the variety Idared, Golden Reinders and Jonagored. For grafting were used marcottes with a diameter of 10,0 mm and graft virus free branches imported from Holland. The bench-grafting was made in March. The plantation in the first field was made in the second part of April. The distance of plantation is 90x35cm. The aerial part was palisated on a bamboo support. In the second field, in spring the annual stems were shortened at a height of 50-60 cm from the grafting’s place. With the appearance of the sylleptic shoots, these shoots are removed and it is left only the terminal shoot. In order to stimulate the shoots ramification and growth in the crown zone, there were applied three methods: V1 – knip-baum with free growth (control variant); V2 – knip-baum with periodical remove of apical leaves at the axle; V3 – knip-baum with application of biological active substances. As a biologic active substance in order to stimulate the growth, it was used the preparation Ecostim with a concentration of 0,25 ml to 1 liter of water. The investigations were made in the field and laboratory conditions according to the required methods of doing experiments with fruit-growing plants. On the basis of the investigations made, it came out that the striking degree of the planted bench graftings in the first field of the fruit nursery constituted in average 93,0-99,3 %. What greatly influenced on the measures on annual growth the biological features of the soil, the plant height varying between the limits of 106 cm (Idared), and 122 cm (Jonagored); the leaf surface of the grafted apple trees under the study was 5,39-6,34 thousand m2/ha. In the second field the development best indicators of the apple trees of “knip baum” type were registered at the formation of the crown basis by periodical remove of apical leaves on the axle where the trees height is 153,7-181,1 cm, the trunk diameter is 15,2-1,0 mm, the number of branches in the crown zone is 6,4-12,7 pieces/tree with an average length of 34,2-55,4 cm, the leaf surface is 0,41- 0,67 m2/tree. The standard apple tree productivity for the varieties taken into the study is between the limits of 29, 11-31,19 thousand pieces/tree.

Repellence of the red bud borer Resseliella oculiperda from grafted apple trees by impregnation of rubber budding strips with essential oils

The red bud borer Resseliella oculiperda (Rübs.) is a pest insect of apple trees when rootstocks are grafted with scion buds by 'shield budding'. The female midges are attracted to the wounds of the grafted buds where they lay their eggs. The larvae feed on the cambium and destroy the buds completely or partially, leading to bad union of the buds with the rootstocks. Budding strips are used very often by growers to bind scion buds to rootstocks. These strips cannot prevent midges from reaching the damaged tissue. Chemical treatments applied to the grafts and other types of strip do not provide better protection against the pest and may cause other risks for growers. In orchard experiments in 2000 and 2001, the authors evaluated the repellent action provided by three essential oils and five compounds of plant origin against the midges by impregnating budding strips with them. The essential oils of lavender, Lavandula angustifolia (P. Mill.), and alpha-terpineol decreased the infestation of buds by more than 95 and 80% respectively. The other potential repellents tested [the essential oil of Juniperus virginiana (L.), citronellal, the essential oil of Cinnamomum camphora (L.) J. Presl, R-carvone, linalool and R-fenchone] decreased infestation by 67, 66, 51, 45, 37 and 25% respectively. The formulation and commercial development of budding strips impregnated with lavender oil is discussed.

EVALUATION OF COMPATIBILITY FOR GRAFTED APPLE-TREES BY THE METHOD OF COINCIDENCE GROWTH RHYTHMS

EVALUATION OF COMPATIBILITY FOR GRAFTED APPLE-TREES BY THE METHOD OF COINCIDENCE GROWTH RHYTHMS

Identification and quantitation by GC-MS of zeatin and zeatin riboside in xylem sap from rootstock and scion of grafted apple trees

Zeatin and zeatin riboside were identified by full-scan gas chromatography-mass spectrometry (GC-MS) in xylem sap of clonal apple rootstocks (M.27, M.9 and MM.106). These rootstocks exhibit a wide range of control over tree size when grafted to a common scion. The concentrations of zeatin and zeatin riboside were measured by GC-MS selected ion monitoring (SIM) in shoot xylem sap and root pressure exudate obtained from these rootstocks and from trees of ‘Fiesta’ scion grafted onto the rootstocks. Zeatin was the predominant cytokinin in xylem sap from the dwarfing rootstocks, M.27 and M.9, while zeatin riboside was the predominant cytokinin in xylem sap from the more invigorating rootstock MM.106. Cytokinin concentrations (ng ml−1) in root pressure exudate and shoot xylem sap, (i.e. from above the graft union in composite trees), increased with increasing vigour of the rootstock, irrespective of whether the plants were non-grafted rootstocks, or were composite plants of ‘Fiesta’ scion grafted onto the rootstocks. Cytokinin content (ng shoot−1) of shoot sap differed with rootstock; the more invigorating (MM.106) had greater amounts of cytokinins than the more dwarfing (M.9 and M.27) rootstocks. These results are discussed in relation to possible influences of roots on the growth of shoots via cytokinin supplies in the xylem sap.

Use of a Three Parameter Rheological Model for Measuring Properties of Wood in Grafted Apple Trees

Use of a Three Parameter Rheological Model for Measuring Properties of Wood in Grafted Apple Trees

THE EFFECT OF TOP ENVIRONMENT AND FLOWERING UPON TOP-ROOT RATIOS

Several papers and many references in other manuscripts have dealt with the relation of growth of the tops and growth of the roots of plants. These generally present data showing the effect of soil types, moisture or mineral elements upon top-root ratio (2, 4, 10). The idea is quite prevalent in some agricultural circles that the relative amount of roots on a plant is determined, if not controlled, by the soil. On the other hand, there are several other factors which can be shown to modify greatly the top-root ratio. Among these are variety, light intensity (10), photoperiod, partial defoliation, girdling, fruiting, and growth substances (14). For example, the amount as well as character of the root system of piece-root grafted apple trees varies with the variety of scion used (5, 9). The type or amount of reserves accumulated in perennial plants as the apple has marked effects upon the subsequent top-root ratio (fig. 1). It has been reported in the literature that plants grown in short days have relatively few roots (1, 11). This conclusion may be strengthened if the plants are not grown to maturity. Also, having few roots in short photoperiods is an effect which may be incidental to the fact that the plants under observation come to flower in short days. Plants which blossom in long photoperiods have been seen to have fewer roots in long photoperiods (6), indicating a correlation between flowering and limited root development. This was found to be the case by Withrow, who used nitrogen supply as a variable with photoperiod (13). She states: ... plants, for the most part, were able to form proportionately larger tops as compared to roots under that photoperiod which brought about flowering as compared to that photoperiod under which the plants remained vegetative. Nitrogen supply did not usually alter the direction of this response, although under either photoperiod there were proportionately larger tops as compared to roots at high nitrogen levels than when the nitrogen supply is limited. ' ' Nitrogen is generally credited with increasing the top-root ratio (2, 4, 10). The data presented in this paper were collected to measure to what extent the ratio of top to root is influenced by some factors in the environment of the top ; also, to see if the relative amount of root formation is consistently related to the function of flowering and fruiting regardless of whether a plant has a greater ratio of roots in short photoperiods, long photoperiods, cool temperatures, warm temperatures or other specific cultural environment.

STOCK-SCION CHEMISTRY AND THE FRUITING RELATIONSHIPS IN APPLE TREES

Mailing Nine or true Paradise apple stock has been vegetatively propagated for centuries as a rootstock for use in the production of dwarf apple trees. Mailing Nine is said to be native to parts of southern Russia (3), and is presumably a type that has adapted itself to semi-arid conditions. stock itself is a low branching shrub, rather than a tree. As to the physiological effects in dwarfing the scions (11) of apple varieties grafted or budded upon it, very little is known. Blackman (1) states: The influence of stock on scion is one which has puzzled plant physiologists for decades. No progress has been made as to the mechanism of the action of a dwarfing stock. ' ' Mailing Twelve stock used in this work is one of extreme vigor among the vegetatively propagated stocks (8), closely approaching the vigor of the free-growing or seedling crab stocks in common use by American nurserymen for the production of standard budded or grafted apple trees. two stocks, Mailing Nine and Mailing Twelve, represent very nearly the extremes in growth habit, vigor, age of fruiting, etc., found in the Pyrus makes species. Of the scion varieties used, is a very low N tree, slowing up in growth at an early age, while Snow is an extremely high N variety, very vigorous in growth. A chemical study of the trees grown on the two stocks just mentioned should reveal something of the chemistry involved in growth extremes in apple, and possibly something of the fruiting relationships as they occur in dwarf and in standard apple trees of different varieties. All apple scion varieties are not affected in the same way by these two Mailing stocks, according to Roberts 's (14) work. Of the varieties studied here, Wealthy is only moderately dwarfed by the Mailing Nine stock, but is fruiting heavily (at the age of 6 years) on a biennial schedule. Mclntosh on Nine is decidedly dwarfed, with characteristically open top, and fruits heavily. Spy, Winesap, and Whitney are severely dwarfed, and are fruitful. All of these varieties as grown on Mailing Twelve stock are as yet entirely unfruitful (with the exception of Wealthy which fruits lightly) and are very vigorous growers. Snow on Nine is not appreciably dwarfed, however, while Snow on Twelve makes a fair growth but does not show the extreme vigor that might be expected from this combination of root and scion. York in