Plant Physiol. 1934 January; 9(1):
GRADIENT COMPOSITION OF ROSE SHOOTS FROM TIP TO BASE1
H. B. TUKEY AND E. L. GREEN
(WITH SIX FIGURES)
|1Approved by the Director of the New York State Agricultural Experiment Station for publication as Journal Paper No. 16.|
In the commercial propagation of plants by means of stem cuttings, it is customary to remove a shoot from the plant and divide it into sections, or "cuttings," which are then placed in the rooting medium. It is common knowledge that the tip cutting from a shoot is less woody than one taken from the middle portion, and that a cutting from the basal portion is in turn still more woody, indicating that the structure and degree of differentiation vary from tip to base.
Moreover, the behavior of cuttings, as regards their rooting responses, varies with the degree of "hardness." SCHRADER (3) has shown for the tomato, and ZIMMERMAN (4) for Weigela and the American pillar rose, that when shoots are cut into segments, there may be a gradient in rooting response from tip to base of one nature or another, depending upon the nature of the material. It is the purpose of this paper to show the gradient in chemical composition throughout the length of rose shoots used for propagation by cuttings. In addition, a comparison is made between plants grown with and without an abundant nitrogen supply.
Gradient in composition from tip to base
MATERIALS AND METHODS
One-year-old, field grown, Rosa multiflora (Thurnb.) plants propagated from one original plant by cuttings were placed in new, 12-inch clay pots in the greenhouse on January 23, 1931, all materials having been steam sterilized. The pots were set in shallow enameled pans, and the plants kept moist from below by maintaining a constant water level in the pans.
Six pots contained rich greenhouse soil high in nitrogen, as judged by plant growth. Six others contained quartz sand and were supplied with mineral nutrients once a week, but no nitrogen. By this means plants were grown for examination and analysis which were of contrasting appearance and composition-the one group with high nitrogen and the other with low nitrogen.
Both lots grew vigorously until the last of March, when the plants in quartz sand with no nitrogen began to slow down in growth, as evidenced by shorter internodes and yellowish foliage. The vigorous growth of these plants for 60 days, however, with no external supply of nitrogen, is interesting. The plants in rich soil were dark green at this time.
By May 4, 101 days after planting, the leaves of the plants receiving no nitrogen were yellowish green with reddish margins and the canes were stiff and yellowish green in color. By contrast, the leaves of plants receiving liberal supply of nitrogen were dark green, and the canes were deep green and flexible. At this time material was cut for chemical analysis.
Several canes approximately 100 cm. in length were taken from both the high-nitrogen and the low-nitrogen plants. The two lots were kept separate, and the canes were cut into sections 10 cm. in length and numbered consecutively from base to tip. The analysis of this material is given in table I. The material from the high-nitrogen or soil-grown plants was numbered L1 to L10, from base to tip respectively. The material from the low-nitrogen or sand-grown plants was numbered D1 to D10, from base to tip respectively.
GRADIENT IN COMPOSITION OF ROSE SHOOTS FROM BASE TO TIP, GROWN WITH HIGH AND LOW NITROGEN
|PLANTS GROWN WITH LOW NITROGEN|
|FRESH MATERIAL||DRY MATERIAL|
|PLANTS GROWN WITH HIGH NITROGEN|
|1We are indebted to F. S. KOKOSKI for these analyses.|
Leaves and petioles were removed and each lot cut into pieces 0.5 to 1 cm. in length, and placed in a covered aluminum moisture dish and dried to constant weight at 80° C., 25 mm. pressure. Total nitrogen and ash were determined by the Chemistry Department of this Station,1 using the Kjeldahl-Arnold-Gunning method for total nitrogen.
The data in table I need no detailed explanation. They show the general increasing gradient for moisture, ash, and total nitrogen from base to tip of rose shoots. They also show the higher moisture, ash, and total nitrogen content of the high-nitrogen plants over the low-nitrogen ones.
How much steeper the gradient becomes as it nears the tip is shown by the analyses of tips in table II, to be compared with the tip cuttings D10 and L10 in table I. Although D10 and L10 were tip cuttings, they were nevertheless 10 cm. in length, whereas samples 4 and 5 in table TI were the distal 2 cm. of the shoot. It would be interesting to know the condition within still narrower limits at and near the growing point.
Figures 1-6 show the distribution and proportionate amount of starch in shoots of similar composition to those used for analyses. The relation between starch accumulation and total nitrogen content is inverse; that is, although nitrogen content is greatest nearest the tip of the shoot, the starch content is lowest.
In the comparison of shoots from plants grown in high and low-nitrogen media, the accumulation of starch is less in the high-nitrogen grown shoots.
Accumulation seems to occur first in the xylem parenchyma, next in the xylem rays, next in the perimedullary zone, next in the cortex parenchyma, next in the pith, and last abundantly in the cortex parenchyma. It is found sparingly in the phloem and rarely in the cambial zone, either fascicular or interfascicular.
In the sections showing greatest accumulation of starch, the greatest abundance is to be found in the xylem rays, perimedullary zone, and cortex parenchyma.
Chemical composition of rose shoots grown with high and low nitrogen
MATERIALS AND METHODS
The material used for analysis was grown and prepared for analysis as already described. The shoots from low-nitrogen plants growing in quartz sand were divided into two lots, nos. 1 and 2. The shoots from the high-nitrogen plants growing in soil were divided as nos. 3 and 6. Entire shoots were used in these analyses, with the exception of 2 cm. of succulent tips, which were cut from each lot and analyzed separately as nos. 4 and 5. The data are given in table II.
ROUTINE ANALYSIS OF ROSE SHOOTS GROWN IN HIGH AND LOW NITROGEN
|FRESH MATERIAL||DRY MATERIAL|
|1||Grown in low N||49.36||1.367||4.59||12.80||26.44||0.177||6.6||2.77||10.09||25.93||52.79||0.3587|
|2||Grown in low N||50.39||1.445||6.23||19.40||19.03||0.2051||8.2||2.87||12.36||38.50||37.76||0.4070|
|3||Grown in high N||38.65||1.337||1.84||14.00||15.67||0.3812||4.9||3.46||4.76||36.22||40.55||0.9860|
|6||Grown in high N*||37.71||1.041||1.95||13.24||15.05||0.3144||6.9||2.76||5.17||35.11||39.91||0.8340|
|5||Tips from plants
grown in low N
|4||Tips from plants
grown in high N
|7||Tips from plants
grown in high N*
plants, intermediate between the other high- and low-nitrogen
†The nitrogen in the hot 80 per cent. alcohol-insoluble residue is regarded as ''protein" although the use of this term is not free from objection.
|FIGS. 1-6. Sectors of transverse sections of rose shoots, showing starch accumulation: figs. 1-3, tip, middle, and basal sections respectively, from a high-nitrogen-grown plant; figs. 4-6, tip, middle, and basal sections respectively, from a low-nitrogen-grown plant.|
Each lot was cut into pieces 0.5 to 1 cm. in length, and placed in a covered aluminum moisture dish and dried to constant weight at 80°C., 25 mm. pressure. The lots of succulent tips, namely, nos. 4 and 5, were then run for total nitrogen. The larger lots, nos. 1, 2, 3, and 4, were ground and again dried and weighed to determine the loss in grinding. Exactly 1 gm. of calcium carbonate was added and the whole sample extracted with hot 80 per cent. alcohol in a Soxhlet apparatus. Reducing sugars, sucrose, starch, and alcohol-soluble and alcohol-insoluble materials were determined by the methods used generally for plant materials at this Station (2), determining the reducing sugars by Bertrand's method (1) and the starch by taka-diastase followed by acid hydrolysis. Corrections were applied to allow for the loss in grinding and for the addition of the calcium carbonate. Crude fiber was determined by the official method.
There is a high percentage of starch in the shoots from plants grown in the medium low in nitrogen (table II), and a lesser amount of starch in the shoots from plants grown in that high in nitrogen. The higher percentage of total nitrogen in shoots from plants grown in high-nitrogen soil is to be expected. Likewise the lower ratio of alcohol-insoluble nitrogen to alcohol-soluble nitrogen is to be expected, inasmuch as theoretically there should be a higher proportion of amino acids and other non-protein forms of nitrogen in actively growing parts.
These results emphasize the differences in composition between sections of a rose shoot 100 cm. in length. When shoots from plants of different growth habit are made into cuttings, there may be as much variation in composition between cuttings from the same shoot as between cuttings from different plants. Accordingly it would seem advisable to keep cuttings from a single shoot in numerical order from base to tip, and to compare the rooting habit of the sequence of cuttings as a whole rather than to make a percentage valuation as though it were a random sample.
STATE AGRICULTURAL EXPERIMENT
GENEVA, NEW YORK
U. S. DEPARTMENT OF AGRICULTURE
WASHINGTON, D. C.