Fourth Node Research Articles

Sequential elongation of internodes of deepwater rice at different water depths

Abstract Deepwater rice (DWR) was grown for four seasons in Thailand where fields were deeply flooded 50–80 days after seedling emergence. After flooding commenced, water levels increased at rates of 2–6 cm/day until reaching maximum depths of 1–3 m. The DWR plants survived by elongation of internodes, thus increasing plant height and keeping the foliage above water. The total number of internodes with marked elongation (5–30 cm) ranged from 14, where water reached a maximum of 1 m to 20 at 3 m maximum water depth, but the five uppermost appeared to elongate under the influence of reproduction rather than water level. New nodes were produced at intervals of 10–12 days, and the most recently formed internodes elongated. The number of internodes formed at the base of the stems during the dryland phase which did not elongate depended on the time of commencement of flooding, but plants appeared able to elongate after production of the fourth node. Grain-yield was not decreased in the deepest water.

EVALUATION OF COWPEA RATOONING POTENTIAL

Two cowpea cultivars, Pinkeye Purple Hull and Royal Blackeye, were evaluated for their ability to produce a ratoon crop. Dry weight and pod yield were measured following harvest from two different cutting heights (second and fourth node), and stages of pod maturity (green and dry). The cultivar Royal Blackeye produced more green manure or returned biomass following ratooning than did Pinkeye Purple Hull. Cutting height and sampling at different pod maturities influenced ratooning potential. These results suggest that cowpea ratooning appears to be economically feasible and that further screening of cowpea cultivars for ratooning ability is warranted.

The response of lateral buds of Pisum sativum to decapitation and selective bud excision

Seedlings of Pisum sativum L. cv. Onward exhibiting complete apical dominance were decapitated above the fourth node and one or more of the four inhibited lateral buds then excised. Lateral bud length and mass were measured as an indicator of the degree of inhibition experienced by each bud as well as the influence of one growing bud on another in the whole shoot system. The results are discussed in relation to theoretical gradients of nutrients and growth regulators in the plant. Saailinge van Pisum sativum L. var Onward wat volkome apikale oorheersing getoon het, is bo die vierde node gedekapiteer en een of meer van die vier geïnhibeerde syknoppe dan verwyder. Laterale knoplengte en -massa is gemeet as ’n aanduiding van die graad van inhibisie langs die stingel. Die resultate word bespreek in terme van teoretiese gradiënte van voedings- en groeistowwe in die plant.

Translocation of nitrogen absorbed by the roots of specific tiller in rice plant.

In order to determine the tiller-to-tiller translocation of nitrogen in rice plants, changes in the percentage content and percentage distribution of absorbed 15 in each tiller and the main stem were investigated by the 15 treatment of the roots of fourth tiller (the fourth tiller in primary tiller was expressed as T4) that emerged from the fourth node of the main stem. The quantity of translocated 15 in tillers after absorption by the roots of T4 was arranged in genealogical order by the site of its distribution as follows: daughter tillers of T4 (T41, T44; secondary tillers) > T4 itself > > mother stem (main stem) > younger sister tillers (T5, T7; primary tillers) that emerged from the upper nodes of the T4 emerging node > elder daughter tillers that emerged from elder sister tiller (niece tiller; T31, T34) > elder sister tiller (T3) that emerged from the lower node of the T4 emerging node. It was made clear that the nitrogen-distribution from T4 to T3 that emerged from lower node of the T4 emerging node and to secondary tillers on T3 was extremely low. It was therefore, presumed that a remarkably small quantity of nitrogen was translocated from tillers that emerged from the upper nodes to tillers that emerged from the lower nodes of the stem in rice plant.

Size-dependent Sex Ratios in the Monoecious, Wind-pollinated Annual, Xanthium strumarium

-I examined the numbers and mass of male and female inflorescences produced by the monoecious, wind-pollinated, self-compatible annual, Xanthium strumarium. Sex ratio (number and mass of male flowers number and mass of female flowers) increased with plant size and resource status for greenhouse plants that were experimentally induced to flower, and for naturally occurring plants. Similarly, plants in low-density sections of an experimental garden were larger and had higher sex ratios than those in high-density sections, presumably because of reduced competition. The observed direction of sex change with plant size was unusual, since most species become more female as plant size increases. Sex ratio in this species appeared to be related to branching pattern. Female inflorescences were produced at all nodes, while male inflorescences were absent from about the second to the fourth nodes of main and side shoots. Whole-plant sex ratio may be determined by these location templates for inflorescences, so conditions that alter branching patterns might have important effects on reproductive allocation and reproductive success.

Spider Mite Control, Trial 2, 1988

Abstract Pesticide performance against a TSSM infestation was evaluated during an unusual outbreak on soybean in Minnesota. Plots of 2 rows (30-inch spacing) by 15 ft were arranged in a randomized complete block design with 5 replicates. A single border row separated adjacent plots to minimize effects of spray drift. Mites were present on nearly every leaf throughout the soybean canopy at stage R5.5 (beginning seed) with feeding injury readily visible below the top 5-6 leaves. Insecticides were broadcast 13 Aug in 30 gal water/acre with a CO2-powered backpack sprayer with 8002 nozzles set at 40 psi. The population in each plot was sampled 12 Aug, 18 Aug, 23 Aug, and 29 Aug (-1, 5, 10, and 16 DAT). On each sampling date, spider mites were counted from 20 leaflets/plot (10 leaflets at the fourth node from the top and 10 leaflets at the eighth node from the top). Leaflets were placed in plastic bags in a cooler for transport to the laboratory. Samples were held at 45°F until mites were removed from the leaflets with a mite-brushing machine. Eggs and mites were counted. Leaf injury was visually estimated on 26 Aug from 5 leaflets/plant (nodes 4-8 from the top) on 5 plants/plot. Plots were harvested 10 Oct, and yields were corrected to 13% moisture.

Spider Mite Control, Trial 1, 1988

Abstract A severe infestation of TSSM provided an unusual opportunity to evaluate insecticide performance in Minnesota. Plots of 2 rows (30-inch spacing) by 15 ft were arranged in a randomized complete block design with 4 replicates. A single border row separated adjacent plots to minimize effects of spray drift. Spider mites were present throughout the soybean canopy at stage R5.5 (beginning seed) with feeding injury readily visible below the top 2-3 leaves. Insecticides were broadcast 13 Aug in 30 gal water at 40 psi using a CO2-powered backpack sprayer with 8002 nozzles. The population in each plot was sampled 13, 18, and 23 Aug (0, 5, and 10 DAT). On each sampling date, TSSM were counted from 20 leaflets/plot (10 leaflets at the fourth node from the top and 10 leaflets at the seventh node from the top). Mites were removed from the leaflets with a mite-brushing machine. Leaf injury was visually estimated from 5 leaflets/plant (nodes 4-8 from the top) on 5 plants/plot. Plots were harvested 10 Oct, and yields were corrected to 13% moisture.

Evaluation of Aphicides in Mississippi, 1987

Abstract Thirteen treatments were tested for relative efficacy against cotton aphids in unirrigated cotton planted 14 May at the Plant Science Research Farm, Mississippi State University, Mississippi State, Miss. Plots were 8 rows (38-inch centers) × 50 ft and were arranged in a randomized complete block design with 4 replications. Treatments were applied to all 8 rows of each plot by high-clearance spray tractor equipped with compressed-air plot spray system calibrated for 5 gal/acre at 4 mph using 3 TX-3 nozzles/row. Applications were made on 24 Jul and } 7 Aug. All plots received insecticide treatments for nontarget pests as needed during the season. Aphids were counted on 10 leaves chosen at random within * the plot from approximately the fourth node down from the terminal. All data were collected from the center 2 rows of each plot, and yield was obtained by ' mechanical picker.

Physiological comparisons of two soybean cultivars differing in canopy photosynthesis. II. Variation in specific leaf weight, nitrogen, and protein components

Cultivar differences in canopy apparent photosynthesis (CAP) have been observed in soybean (Glycine max (L.) Merr.) but little is known about the physiological mechanisms which are responsible for such differences. This study was initiated to determine if variation in ribulose 1,5-bisphosphate carboxylase (RuBPCase) and soluble protein exists among cultivars which differ in CAP during reproductive growth. In addition, the relationship between specific leaf weight (SLW) and leaf protein was examined. Two Maturity Group VI cultivars, 'Tracy' (high CAP) and 'Davis' (low CAP), were grown in the field during 1979, 1980, and 1981 and in a greenhouse experiment. Leaves located at two canopy positions (topmost, fully expanded leaf and eighth node from the top) in 1979 and three canopy positions (those mentioned, plus the fourth node from the top) in 1980 and 1981 were sampled. Leaves at the two upper canopy positions exhibited greater SLW, RuBPCase m(-2), and soluble protein m(-2) than found at the eighth node down. Photosynthetic capacity of leaves at inner canopy regions was therefore affected by both light penetration into the canopy and leaf protein status. Over the three year period, the SLW was 23 percent and the soluble protein m(-2) leaf 21 percent greater in Tracy than in Davis. Although the trend in RuBPCase m(-2) leaf was not significant, it was consistently greater in Tracy in the field and greenhouse. No cultivar differences were observed when the proteins were expressed on a unit of leaf dry weight. The quantity of RuBPCase per unit leaf area was positively correlated with SLW with significant partial correlation coefficients of 0.62, 0.67, 0.35, and 0.82 for 1979, 1980, 1981, and the greenhouse study, respectively. Since these cultivars have similar leaf area indices during September, the greater SLW of Tracy is translated into more photosynthetic proteins per unit ground area and higher CAP rate.

Floral determination in axillary buds of Nicotiana silvestris

At anthesis of the terminal flower the developmental fates of axillary buds of the long-day plant Nicotiana silvestris were assessed in situ and in isolation. The in situ developmental fate was assessed by decapitating the plant above the bud in question and letting the bud mature. The developmental fate of isolated buds was assessed by removing the bud from the main axis, rooting it, and letting it mature. The number of nodes below the terminal flower of the mature shoot was indicative of the developmental fate of the bud. Terminal meristems of rooted axillary buds exhibited two patterns of development: (1) Their developmental fate was the same as that of in situ buds at the same node or (2) their developmental fate was the same as that of seed-derived plants. For example, terminal meristems of rooted buds from the fourth node below the inflorescence produced either 15 to 19 nodes or 36 to 40 nodes. In situ fourth buds produced 12 to 14 nodes while seed-derived plants produced 33 to 39 nodes. Terminal meristems of rooted axillary buds that exhibited the same developmental fate as that of in situ buds were determined for floral development. Although determined buds produced a terminal flower, all but one had abnormal inflorescences. That is, in the place of floral branches determined buds produced vegetative branches. Four buds that were not determined for floral development had their shoot tips rooted each time the plant bolted. Only when the plants were allowed to grow without being rerooted did they flower. These results indicate that roots may prevent and/or destabilize floral determination in N. silvestris.

Preformation of root primordia in shoots and root morphogenesis in Salix viminalis

Root primordia are formed in the stems of Salix viminalis L. during normal growth. Some of these primordia are produced at definite sites in the nodes. The initiation and early structural and ultrastructural development of the nodal primordia were studied in young shoots. In the fourth node below the terminal leaf cluster some parenchyma cells situated at the lateral leaf gaps formed a small group of initial cells. Derivatives of the newly formed interfascicular cambium added cells to that group, in which later on cell divisions in various directions occurred resulting in the formation of a root primordium. Root morphogenesis was studied in cuttings from one‐season‐old stems. The cells in the dormant primordia contained many lipid bodies but only a small amount of starch. After the cuttings had been 24 hours in water starch was accumulating in the plastids and lipid bodies were seen in the vacuoles. 48 hours after activation cell divisions occurred throughout the primordia and a layered apical mer‐istem was organized. After 96 hours a root cap with amyloplasts was formed and the procambium was well developed. The amyloplasts were sedimented in response to gravity. After six days the first roots were ready to emerge from the stems. Their root caps had a well developed columella and endodermal and pericyclic cells were recognizable.

EFFECT OF SEED SIZE ON HETEROBLASTIC DEVELOPMENT IN SEEDLINGS OF DESMODIUM PANICULATUM

Seedlings of Desmodium paniculatum derived from different seed sizes differed in heteroblastic development. The transition from juvenile to adult leaves took place at the fourth node in seedlings derived from larger seeds and at the fifth or sixth node in those derived from smaller ones. Cotyledon removal had no effect on this condition, but growth under reduced irradiance delayed the formation of adult leaves in seedlings from larger seeds. Simple and compound leaves had similar unit area photosynthetic rates and stomatal conductance values, but compound leaves had a 30% higher total area. The earlier production of adult leaves would thus give seedlings from larger seeds an advantage in terms of total carbon gain.

The Taxonomic Significance of Plumule Morphology in Ceratophyllum (Ceratophyllaceae)

The plumule morphology of species of Ceratophyllum was studied for purposes of: 1) determining extent of variability in forking of first epicotyl leaves, and 2) evaluating plumule features as taxonomic characters by assessing interspecific and intraspecific (interand intrapopulational) variation. Embryos from specimens collected throughout ranges of eight of species (Ceratophyllum australe, C. demersum, C. Ilerenae, C. muricatum, C. oryzetorum, C. platyacanthum, C. submersum, and C. tanaiticum) exhibited no variation in morphology of first epicotyl leaves. all instances leaves were simple. addition, no intrapopulational variation in was detected in C. demersum, C. llerenae, or C. submersum (rarity of material prohibited study of intrapopulational variation in other five species). contrast, embryos from specimens collected throughout range of ninth species, C. echinatum, possessed forked leaves at all nodes of plumule. C. echinatum, interpopulational variability was observed in number of segments produced by forked plumule leaves at first node. The segment number is not correlated geographically, and combinations of segment number can be observed within a single population. The unusual plumule morphology of C. is distinctive within genus and has probably resulted from phylogenetic reduction of lower plumule axis. These observations support recognition of C. as a distinct species. The embryo morphology of Ceratophyllum has been interpreted variously since early studies of its structure in 18th century. Gaertner (1788) provided a preliminary description of embryo, but regarded two cotyledons as a separate organ, vitellus (Aboy 1936; Schleiden 1837). Richard (1808) described embryo of Ceratophyllum with four cotyledons rather than two. Brongniart (1827) considered possibility that in Ceratophyllum, cotyledons represent outgrowths of radicle, in which case first foliage leaves constitute true cotyledons. Schleiden (1837, 1838) was first to identify correctly two cotyledons of Ceratophyllum based upon his discovery of epicotyledonary internodes in some mature seeds. Most botanists eventually recognized embryo of Ceratophyllum with two cotyledons, above which a pair of simple, decussate plumule (epicotyl) leaves arise. Arber (1920) further remarked that forked leaves do not occur in plumule until fourth node above cotyledons, but are preceded by juvenile (simple, linear) leaves. 1936, however, an important observation was made by Aboy (1936) who studied Ceratophyllum demersum and poorly known eastern American species C. echinatum. She reported a difference in leaf morphology at first plumule node between two species (Aboy 1936, p. 25): In young plant of C. demersum var. echinatum [=C. echinatum], the first pair of leaves may fork once or twice .... young plant of C. demersum, . . . first pair of leaves never fork[s]. Aboy based her conclusion upon examination of only one collection of fruits of C. echinatum, so a fundamental distinction between plumule-leaf forking characters of individuals of C. demersum and C. throughout their ranges could only be implied. Evidence supporting Aboy's work appeared soon afterwards in a paper by her mentor, W. C. Muenscher (1940), who concluded that not only did seedlings of C. demersum and C. exhibit different plumule morphologies at first node above cotyledons (as Aboy described), but at second node as well. At that level, C. demersum consistently produced simple leaves only, whereas seedlings of C. produced forked leaves at all plumule nodes. As Arber (1920) had already observed, he found that forked leaves did not occur in C. demersum until third or fourth node above cotyledons. Muenscher (1940, p. 232) regarded these seedling differences to be most constant character with which to separate C. demersum and C. echinatum,

Ultrastructure of elliptical and diffuse bundles in the vegetative nodes of rice.

The second and fourth nodes from the top of rice culm were harvested at the times of flag leaf emergence and heading respectively. Ultrastructural observation has been made on the elliptical and diffuse bundles in particular reference to solute movement in the node. 1. In the phloem of elliptical bundles, which are continuous with the large bundles of leaf, both the sieve elements and phloem parenchyma cells increased in number and showed a ratio of about one to two. A sieve element was connected by plasmodesmata with the plural number of phloem parenchyma cells (Fig. 1). In the border region between phloem and xylem, the parenchyma cells with dense cytoplasm were interconnected by plasmodesmata (Fig. 2). It is assumed that the solutes actively move in the symplast between phloem and xylem. 2. The elliptical bundles contain numerous xylem transfer cells, in which the wall ingrowths were formed on the walls contacting with tracheary elements. The mitochondria with developed cristae and the plastids with peripheral reticulums were contained in the xylem transfer cells (Figs. 3 and 4). A large amount of plasmodesmata was found in the walls between xylem transfer cells and bundle sheath cells, between bundle sheath cells and fundamental parenchyma cells and also between fundamental parenchyma cells (Figs. 4, 5, 6 and 7). It can be (considered that the solutes absorbed from transpiration stream by xylem transfer cells are transferred actively to fundamental parenchyma via bundle sheath cells. 3. In the phloem of diffuse bundles which are surrounding the elliptical bundles and are continuous with the large bundles of internode, the number of sieve elements was about 3.5 times as many as phloem parenchyma cells and the sieve elements were partitioned by numerous sieve plates (Fig. 8). The phloem parenchyma cells of diffuse bundle contained abundant mitochondria, plastids, rough endoplasmic reticulum and ribosomes (Figs. 9 and 10). It is suggested that the phloem parenchyma cells play an important role in climbing of photosynthate in the phloem of diffuse bundle through energy supply.

Changes in carbohydrate and enzyme levels during the sink to source transition of leaves of Cucumis sativus L., a stachyose translocator

The sink to source transition of expanding leaves of cucumber was studied by sampling leaves sequentially from the growing stem apex toward the base of the plant. Leaf fresh weight and photosynthetic rate increased in the progression to lower nodes. Sucrose and raffinose concentrations were higher in sink leaves than in source leaves. Galactinol and stachyose concentrations increased during leaf expansion. Both alkaline and acidic α-galactosidase activity declined during leaf expansion, whereas galactinol synthase activity increased abruptly in leaves beginning in the leaf at the fourth node below the apex. This increase in activity corresponded temporally to marked changes in the oligosaccharide composition of the leaves in favor of galactosyl-saccharides, particularly stachyose. Across all leaf positions, galactinol synthase correlated positively with galactosyl-oligosaccharide concentration ( r = 0.90) and correlated negatively with sucrose concentration ( r = −0.82). The ratio of stachyose to raffinose correlated positively with the ratio of galactinol synthase to α-galactosidase ( r = 0.95). The results point to the importance of changes in enzyme levels per se as determinants of changes in soluble carbohydrate levels associated with acquisition of export capability during leaf expansion.

Robbing of Field Bean Flowers by the Short-Tongued Bumble BeeBombus TerrestrisL.

SummaryMost flowers produced during early flowering of autumn-sown field beans had small holes in the base of the corolla which indicated that they had been robbed by Bombus terrestris. The proportion of robbed flowers decreased as flowering continued. Slightly fewer flowers of spring-sown plants were robbed. There was no evidence of damage to the reproductive structures of 100 robbed flowers of the cultivar Maris Bead. Of the flowers sampled from the third, fourth and fifth flowering nodes of field bean plants growing near shelter at the paddock margin, 62% were robbed. Of the pods which subsequently formed at these nodes 59% were from flowers which had been robbed. This suggests that robbing of the flower by short-tongued bumble bees did not prejudice either pollination by other insects or pod development.

Fruit and seed development in mung beans (Phaseolus aureusRoxb.)

SummaryA study of fruit set at different nodes was made in mung beans,Phaseolus aureusRoxb., under field conditions. Flowering commenced on the fourth node from the base and the percentage fruit set showed a gradual decrease from the fifth node upwards. Yield analysis was carried out for each of the fruiting nodes. When the leaf and inflorescences at a node are taken as a functional unit it is seen that there was a decrease in the ratio of leaf area to fruit and seed weights from the base of the plant upwards indicating that at the upper nodes particularly, some other plant parts also contribute to the photosynthate pool of the developing seeds.A quantitative study of the dry matter, proteins and starch in the fruit wall and seeds of fruits at different stages of development was made. It showed that the rapid increase in dry matter, proteins and starch in the seeds at the later stages of development is compensated, in part, by a decrease of these components in the fruit wall. Histochemical studies of the fruit wall further supported these observations. This indicated the contribution of substrates by the fruit wall to the developing seeds.

Relationship Between Grain and Straw Yield with Measurable Morphological Characters in Pearl Millet

A study of the morphological features and yield components relative to the yield of grain and straw of Hybrid pearl millet (Var. HB 1) was undertaken to evolve predi- ction formulas for grain and straw yields. The strongest relationship exists between yield of grain and straw while plant height, productive tillers and length of the ear also. make some significant contribution to the grain yield. In the case of straw, plant height seems to contribute most, followed by length and diameter of main ear and diameter of the fourth node.

Rt esponse of Cotton to Boron1

AbstractField experiments were conducted with rates and methods of application of B to cotton. Broadcast was as effective as drilled, foliar application was as good as soil application, and there was no advantage to a combination of soil and foliar application. A highly soluble source of B was superior to a more slowly soluble one.Young leaves, the third or fourth node from the growing point, were found to have a critical level of about 15 ppm B. Mature leaves occurring at the fifth and sixth nodes from the growing point had a B content of 5 to 10 ppm higher. The critical level of hot‐water soluble B in the top 15 cm of soil was in the range of 0.10 to 0.16 ppm.

Preformed adventitious root initiation in brittle willows grown in a controlled environment

Nodal preformed adventitious root primordia of brittle willow develop from initial cells which appear first and only in the fourth node below the terminal leaf cluster of plants grown under the described environmental conditions. The onset of root initial formation is related to the cessation of rapid aerial development which occurs at node 4, and also with the start of secondary thickening which occurs in this node. Brittle willow is an ideal subject with which to study the cellular physiology of root initials since nodes showing the earliest stages of root initial formation and development can be selected. In addition, the root initials are readily located in histological preparations.