Apical Bud Growth Research Articles

HacA, a key transcription factor for the unfolded protein response, is required for fungal development, aflatoxin biosynthesis and pathogenicity of Aspergillus flavus

Aspergillus flavus is a fungus notorious for contaminating food and feed with aflatoxins. As a saprophytic fungus, it secretes large amounts of enzymes to access nutrients, making endoplasmic reticulum (ER) homeostasis important for protein folding and secretion. The role of HacA, a key transcription factor in the unfolded protein response pathway, remains poorly understood in A. flavus. In this study, the hacA gene in A. flavus was knockout. Results showed that the absence of hacA led to a decreased pathogenicity of the strain, as it failed to colonize intact maize kernels. This may be due to retarded vegetable growth, especially the abnormal development of swollen tips and shorter hyphal septa. Deletion of hacA also hindered conidiogenesis and sclerotial development. Notably, the mutant strain failed to produce aflatoxin B1. Moreover, compared to the wild type, the mutant strain showed increased sensitivity to ER stress inducer such as Dithiothreitol (DTT), and heat stress. It also displayed heightened sensitivity to other environmental stresses, including cell wall, osmotic, and pH stresses. Further transcriptomic analysis revealed the involvement of the hacA in numerous biological processes, including filamentous growth, asexual reproduction, mycotoxin biosynthetic process, signal transduction, budding cell apical bud growth, invasive filamentous growth, response to stimulus, and so on. Taken together, HacA plays a vital role in fungal development, pathogenicity and aflatoxins biosynthesis. This highlights the potential of targeting hacA as a novel approach for early prevention of A. flavus contamination.

Gibberellin-induced Stem Elongation and Apical Bud Growth Acceleration Without Decreased Yield in Broccoli (<i>Brassica oleracea</i> L. var. <i>Italica</i>)

In Japan, broccoli (Brassica oleracea L. var. Italica) is primarily harvested manually. Some Japanese broccoli cultivars have short stems, but these broccoli heads are more difficult to harvest, and complicate the introduction of mechanical harvesters. Therefore, research is focused on strategies to control stem length. The present study examined the effects of the plant hormone gibberellin (GA) on the morphological and agronomic traits of broccoli shoots. The broccoli cultivar ‘SK9-099’, widely distributed in Japan and characterized by a short stem, was studied. These experiments were conducted over three cropping seasons, i.e., spring (Exp. 1), summer (Exp. 2), and fall (Exp. 3), with four GA treatment plots at 0 ppm (Control), 20 ppm, 100 ppm, and 500 ppm. This study observed that, on average, GA elongated stem length from approximately 16.0 cm in the control plot to 24.7 cm in the 500 ppm plot for the three cropping seasons, without decreasing yield. In addition, GA treatment accelerated apical bud growth and shortened the overall growth period by 16 days in the 500 ppm plot compared to the control in the fall, equivalent to 20.5% of the growth period from transplantation to harvest in the latter.This study highlights several practical benefits of GA application for growers, minimizing manual harvesting labor, avoid the difficult of designing mechanical harvesters for short-stemmed cultivars, and increase field usage efficiency by shortening the growth period.

Growth and Flowering of Saffron (Crocus sativus L.) with Three Corm Weights under Different LED Light Qualities

• Saffron (Crocus sativus L.) is referred ‘red gold’ worldwide as it is the most expensive spice. • The cultivation of saffron has been limited due to low flower yields. • Light emitting diode (LED) emits monochromatic light, which can improve crop quality and yield. • The effects of LED supplementation on growth and flowering of saffron ( Crocus sativus ) with three corm weights were studied. • Monochromatic red light significantly promoted saffron growth and increase stigmas yields with three corm weights. Saffron ( Crocus sativus L.) is a flowering plant whose dried stigma is an expensive and well-known spice. The major goal in saffron cultivation is to improve flower quality and yield. The present research aimed to understand the influence of LED light quality on the growth and flowering of saffron and provide valuable guidance to explore modern techniques to promote flower and stigma yield. The growth characteristics, flowering characteristics, hormone and nutrient content, and stigma quality and value were determined at three different corm weights (20–25 g, 25–30 g, 30–35 g per corm) under six LED light qualities [white (control, CK); monochromatic blue light (B); monochromatic red light (R); red and blue light at 1:2 ratio (R1B2); red and blue light at 1:1 ratio (R1B1); red and blue light at 2:1 ratio (R2B1)]. Monochromatic red light reduced corm biomass loss, accelerated apical bud growth, enhanced flower size and number, and advanced flowering. Monochromatic red light significantly increased the indole-3-acetic acid (IAA), soluble protein (SP), and zeatin riboside (ZR) levels in the mature corms compared with CK. Besides, red light demonstrated the highest hormone and nutrient content for the 30–35 g corm weight. Furthermore, monochromatic red light improved stigma yield (total dry weight), total crocin production, and the practical value ratio of saffron. The present study's observations indicate that monochromatic red light promoted saffron growth, advanced flowering, and increased stigma yield by regulating the corm phytohormones and enzyme activity. The study provides valuable guidance to explore modern techniques to promote saffron flower and stigma yield.

Morphogenetic and physiological effects of LED spectra on the apical buds of Ficus carica var. Black Jack

The use of artificial light sources such as light-emitting diodes (LEDs) has become a prerequisite in tissue culture studies to obtain morphogenetic enhancements on in vitro plants. This technology is essential for developmental enhancements in the growing plant cultures due to its light quality and intensity greatly influencing the in vitro growing explants at a cellular level. The current study investigates the effects of different light-emitting diode (LED) spectra on the growth of apical buds of Ficus carica var. Black Jack. Ficus carica, commonly known as figs is rich in vitamins, minerals, and phytochemicals capable of treating microbial infections and gastric, inflammatory, and cardiac disorders. Apical buds of Ficus carica var. Black Jack, presented morphogenetic changes when grown under six different LED spectra. The highest multiple shoots (1.80 per growing explant) and healthy growing cultures were observed under the blue + red LED spectrum. Wound-induced callus formation was observed on apical buds grown under green LED spectrum and discolouration of the growing shoots were observed on the cultures grown under far-red LED spectrum. Multiple shoots obtained from the blue + red LED treatment were rooted using 8 µM indole-3-acetic acid (IAA), and the rooted plantlets were successfully acclimatised. Compared with the other monochromatic LEDs, blue + red proved to be significantly better for producing excellent plant morphogeny. It is apparent that blue and red LED is the most suitable spectra for the healthy development of plants. The findings have confirmed that the combination of blue + red LED can potentially be used for enhancing growth yields of medicinally and commercially important plants.

Defining Functions of Mannoproteins in Saccharomyces cerevisiae by High-Dimensional Morphological Phenotyping.

Mannoproteins are non-filamentous glycoproteins localized to the outermost layer of the yeast cell wall. The physiological roles of these structural components have not been completely elucidated due to the limited availability of appropriate tools. As the perturbation of mannoproteins may affect cell morphology, we investigated mannoprotein mutants in Saccharomyces cerevisiae via high-dimensional morphological phenotyping. The mannoprotein mutants were morphologically classified into seven groups using clustering analysis with Gaussian mixture modeling. The pleiotropic phenotypes of cluster I mutant cells (ccw12Δ) indicated that CCW12 plays major roles in cell wall organization. Cluster II (ccw14Δ, flo11Δ, srl1Δ, and tir3Δ) mutants exhibited altered mother cell size and shape. Mutants of cluster III and IV exhibited no or very small morphological defects. Cluster V (dse2Δ, egt2Δ, and sun4Δ) consisted of endoglucanase mutants with cell separation defects due to incomplete septum digestion. The cluster VI mutant cells (ecm33Δ) exhibited perturbation of apical bud growth. Cluster VII mutant cells (sag1Δ) exhibited differences in cell size and actin organization. Biochemical assays further confirmed the observed morphological defects. Further investigations based on various omics data indicated that morphological phenotyping is a complementary tool that can help with gaining a deeper understanding of the functions of mannoproteins.

ФЕНОЛОГІЯ РОЗКРИВАННЯ БРУНЬОК У РІЗНИХ КЛОНІВ ТОПОЛЬ ТА ВЕРБ

In the face of global climate changes, studies of bud burst and bud set phenology in trees are necessary to determine the duration of the growing season of plants, the optimal planting period, and seasonal works to achieve high productivity. The purpose of our study was to investigate bud burst phenology in different poplar and willow clones, what is important for predicting possible responses of woody plants to climate changes. Materials and methods: Bud burst phenology in poplar and willow was monitored both on the plants growing at experimental plot and on potted plants. Open-field plant research was conducted on a test site of fast-growing bioenergy trees in the M.M. Gryshko National Botanical Garden of NAS of Ukraine (Kyiv). Nine most productive poplar and willow clones were selected for the potted experiment. Throughout the growing season, the plants were kept outdoors, and after the seasonal fall of the leaves, the plants were transferred to an unheated storage room with a limited light regime. During spring, bud burst phenology was screened weekly through 45 days according to the 6-scores scale. The studies showed that the poplar plants grown under laboratory conditions demonstrated faster rates of bud burst compared to the willows, while the plants at the experimental plot, on the contrary, shown faster bud burst in the willows comparing to poplar clones. Such effects may be caused by the restricted light regime at the laboratory space what probably had stronger impact on the bud burst in willows, and in the case of open-field plants also by other random environmental factors. In potted conditions, willows demonstrated a tendency for faster flushing of lateral buds, while most poplar clones showed faster apical bud growth under the same conditions.

Anti-tumor mechanism of Artemisia annua based on bioinformatics

This paper was aimed to explore the relationship between Artemisia annua and tumor, and investigate its anti-tumor mechanism based on the bioinformatics molecular network analysis, text mining technique and other related methods. Text mining tool Polysearch database was used to get the information, and after formatting conversion, the information was imported into the bioinformatics analysis software Cytoscape3.2.1 for visualization and subsequent bioinformatics molecular network analysis .It was shown that the A. annua was associated with the tumor by 8 key proteins： TNF,VEGF,PI3K, ALDH1, Bcl-2, MicroRNA, p38 and CASP3 by text mining technique. The main biological processes involved in its anti-tumor effect included cell cycle, post-translational protein modification, cell cycle regulation, protein ubiquitination and organelle tissues regulation. The key network analysis showed that the action may be achieved by regulation of triglyceride metabolic process, positive regulation of triglyceride metabolic process, positive regulation of triglyceride catabolic process, regulation of budding cell apical bud growth, negative regulation of mitotic cell cycle, negative regulation of meiotic cell cycle, and positive regulation of transcription factors. The results showed that the anti-tumor effect of A. annua may be associated with regulating lipid metabolism of tumor cells, decomposing large amounts of lipids, releasing energy, reducing the rate of tumor cell division and accelerating tumor cell apoptosis.

Application of earthworm urine via apical bud or stem- base: Differential effects on the growth of organs of the leafy-vegetable amaranthus

The present study was undertaken to determine how direct administration of earthworm urine to the apical bud or to the stem-base of the leaf-vegetable crop amaranthus affected the growth performance of the apical and axillary buds, stem girth and roots of the crop. Apical application significantly facilitated the growth of both apical and axillary buds, and the general growth of the whole plant. For agricultural mandates that focus on the production of apical and axillary buds (eg, production of teas), yield can be stimulated by applying low earthworm urine concentration at the stem base, or medium and high concentration of earthworm urine on the apical buds. Application of medium to high concentration of earthworm urine at stem base produces inhibitory effects on the growth of apical buds, axillary buds, stem girth and roots. This result will find commercial and technological applications if relevant farmers could: (1) have a vermin culture to aseptically produce earthworm urine, (2) mix the urine with oil to reduce evaporation when applied, and (3) air-spray by helicopter on his or her farm. Significantly improved yield is expected. Potential beneficiaries of such technology include tea farmers whose products enjoy premium value when restricted to the apical and axillary buds and their immediate neighboring young foliage leaves. Similarly, pharmacognosists and herbal practitioners could apply the principles to increase their harvest of pharmacologically active products harvestable from buds and fresh foliage leaves. Key words: Earthworm urine, tea farming, axillary buds, apical buds, plant growth hormone, herbal extraction.

Molecular Mapping and Identification of QTLs for Fiber Micronaire on Chromosome 7 from Gossypium klotzschianum

Gossypium klotzschianum, carrying the elite alleles, is a diploid species of D genome originated from Galapagos Island, harboring the lethal genes to cause inconsistency of apical bud growth. In this research, we overcame the obstacle and established a BC1F2 population derived from (Simian 2 × G. klotzschianum) × Simian 2 (G. hirsutum). The SSR marker NAU1362 on chro-mosome 7 showed significant correlation with micronaire value by single marker analysis. The BC2F3 and BC2F4 populations were developed from the cross between BC1F2 individuals containing target segments of chromosome 7 from G. klotzschianum and recurrent parent Simian 2. The software Cartographer (V2.5) and the composite interval mapping were further employed to identify quantitative trait loci (QTL) associated with fiber micronaire in two generations. The fiber micronaire QTL qFMIC-7-1 identified in BC1F2 population was confirmed in BC2F3 and BC2F4, which explained 9.0% and 8.8% of the phenotypic variances, respectively. The G. klotzschianum allele decreased the fiber micronaire value. Another micronaire QTL, qFMIC-7-2, on chromo-some 7 was also detected in BC2F3 and BC2F4 generations with phenotypic variance of 3.7% and 4.7%, respectively. Simian 2 was genotyped as decreased micronaire value. These results provide valuable resources for effectively utilization of potential elite genes from G. klotzschianum.

Isolation and expression pattern of genes related to flower initiation in the evergreen azalea, Rhododendron × pulchrum ‘Oomurasaki’

The flowering of the evergreen azalea, ‘Oomurasaki’ ( Rhododendron × pulchrum), extended over two seasons was studied. During the first season, most of the shoot apical meristems transformed into floral meristems and formed flower buds in August. After the dormancy of the flower buds from November to February, flower bud development continued during the second season and flowering occurred in May. To ascertain the approximate period of flower initiation, we monitored the spring shoot and apical bud growth. The putative period for flower initiation was indicated to occur between late June and August. To identify the genes involved in flower initiation, we isolated homologs of the putative flowering-related genes, LEAFY ( LFY), TERMINAL FLOWER 1 ( TFL1), and APETALA 3 ( AP3), and investigated their expression patterns in the shoot apex and apical buds during the first season using Reverse Transcription-quantitative PCR (RT-qPCR). We founding that RpLFY expression increased continually from 14 July to 4 August but that RpTFL1 expression showed trends toward a decrease during the increasing RpLFY expression in apical parts. Subsequently, RpAP3 expression began to increase on 4 August. Collectively, the results estimated that RpLFY and RpTFL1 are involved in flower initiation in ‘Oomurasaki’. We propose that the increased expression of RpLFY and the decreased expression of RpTFL1 at late July mark the beginning of flower initiation.

Comprehensive and quantitative analysis of yeast deletion mutants defective in apical and isotropic bud growth

To obtain a comprehensive understanding of the budding phase transition, 4,711 Saccharomyces cerevisiae haploid nonessential gene deletion mutants were screened with the image processing program CalMorph, and 35 mutants with a round bud and 173 mutants with an elongated bud were statistically identified. We classified round and elongated bud mutants based on factors thought to affect the duration of the apical bud growth phase. Two round bud mutants (arc18 and sac6) were found to be defective in apical actin patch localization. Several elongated bud mutants demonstrated a delay of cell cycle progression at the apical growth phase, suggesting that these mutants have a defect in the control of cell cycle progression.

Proteins involved in sterol synthesis interact with Ste20 and regulate cell polarity

The Saccharomyces cerevisiae p21-activated kinase (PAK) Ste20 regulates various aspects of cell polarity during vegetative growth, mating and filamentous growth. To gain further insight into the mechanisms of Ste20 action, we screened for interactors of Ste20 using the split-ubiquitin system. Among the identified proteins were Erg4, Cbr1 and Ncp1, which are all involved in sterol biosynthesis. The interaction between Ste20 and Erg4, as well as between Ste20 and Cbr1, was confirmed by pull-down experiments. Deletion of either ERG4 or NCP1 resulted in various polarity defects, indicating a role for these proteins in bud site selection, apical bud growth, cell wall assembly, mating and invasive growth. Interestingly, Erg4 was required for the polarized localization of Ste20 during mating. Lack of CBR1 produced no detectable phenotype, whereas the deletion of CBR1 in the absence of NCP1 was lethal. Using a conditional lethal mutant we demonstrate that both proteins have overlapping functions in bud morphology.

Tea (Camellia sinensis) clones with shorter periods of winter dormancy exhibit lower accumulation of reactive oxygen species

Tea (Camellia sinensis (L.) O. Kuntze) is a perennial crop grown throughout the world. During winter, tea undergoes a dormancy period when growth of apical buds almost ceases, severely reducing the commercial yield of tea. Low temperatures prevail during the period of winter dormancy, which alone or in combination with high solar irradiance have the potential to induce oxidative stress in plants. We studied six tea clones under field conditions to test whether a relationship exists between oxidative stress and winter dormancy. Data on the behavior of the enzymatic antioxidative system was collected for all clones during different phases of winter dormancy. There was a strong positive correlation among clones between accumulation of reactive oxygen species (ROS) and the length of the dormancy period. Clones having shorter dormancy periods exhibited higher induction of antioxidative enzymes. Results suggest that efficient scavenging of ROS is a desirable feature in tea because it leads to lower accumulations of ROS during winter months and is associated with reduced winter dormancy.

Overexpression of a bacterial 1-deoxy-D-xylulose 5-phosphate synthase gene in potato tubers perturbs the isoprenoid metabolic network: implications for the control of the tuber life cycle

Potato tubers were engineered to express a bacterial gene encoding 1-deoxy-D-xylulose 5-phosphate synthase (DXS) in order to investigate the effects of perturbation of isoprenoid biosynthesis. Twenty-four independent transgenic lines out of 38 generated produced tubers with significantly elongated shape that also exhibited an early tuber sprouting phenotype. Expression analysis of nine transgenic lines (four exhibiting the phenotype and five showing a wild-type phenotype) demonstrated that the phenotype was strongly associated with dxs expression. At harvest, apical bud growth had already commenced in dxs-expressing tubers whereas in control lines no bud growth was evident until dormancy was released after 56-70 d of storage. The initial phase of bud growth in dxs tubers was followed by a lag period of approximately 56 d, before further elongation of the developing sprouts could be detected. Thus dxs expression results in the separation of distinct phases in the dormancy and sprouting processes. In order to account for the sprouting phenotype, the levels of plastid-derived isoprenoid growth regulators were measured in transgenic and control tubers. The major difference measured was an increase in the level of trans-zeatin riboside in tubers at harvest expressing dxs. Additionally, compared with controls, in some dxs-expressing lines, tuber carotenoid content increased approximately 2-fold, with most of the increase accounted for by a 6-7-fold increase in phytoene.

A positive feedback loop stabilizes the guanine-nucleotide exchange factor Cdc24 at sites of polarization.

In Saccharomyces cerevisiae, activation of Cdc42 by its guanine-nucleotide exchange factor Cdc24 triggers polarization of the actin cytoskeleton at bud emergence and in response to mating pheromones. The adaptor protein Bem1 localizes to sites of polarized growth where it interacts with Cdc42, Cdc24 and the PAK-like kinase Cla4. We have isolated Bem1 mutants (Bem1-m), which are specifically defective for binding to Cdc24. The mutations map within the conserved PB1 domain, which is necessary and sufficient to interact with the octicos peptide repeat (OPR) motif of Cdc24. Although Bem1-m mutant proteins localize normally, bem1-m cells are unable to maintain Cdc24 at sites of polarized growth. As a consequence, they are defective for apical bud growth and the formation of mating projections. Localization of Bem1 to the incipient bud site requires activated Cdc42, and conversely, expression of Cdc42-GTP is sufficient to accumulate Bem1 at the plasma membrane. Thus, our results suggest that Bem1 functions in a positive feedback loop: local activation of Cdc24 produces Cdc42-GTP, which recruits Bem1. In turn, Bem1 stabilizes Cdc24 at the site of polarization, leading to apical growth.

Endoplasmic reticulum dynamics, inheritance, and cytoskeletal interactions in budding yeast.

The endoplasmic reticulum (ER) in Saccharomyces cerevisiae consists of a reticulum underlying the plasma membrane (cortical ER) and ER associated with the nuclear envelope (nuclear ER). We used a Sec63p-green fluorescent protein fusion protein to study motility events associated with inheritance of cortical ER and nuclear ER in living yeast cells. During M phase before nuclear migration, we observed thick, apparently rigid tubular extensions emanating from the nuclear ER that elongate, undergo sweeping motions along the cell cortex, and shorten. Two findings support a role for microtubules in this process. First, extension of tubular structures from the nuclear ER is inhibited by destabilization of microtubules. Second, astral microtubules, structures that undergo similar patterns of extension, cortical surveillance and retraction, colocalize with nuclear ER extensions. During S and G(2) phases of the cell cycle, we observed anchorage of the cortical ER at the site of bud emergence and apical bud growth. Thin tubules of the ER that extend from the anchored cortical ER display undulating, apparently random movement and move into the bud as it grows. Finally, we found that cortical ER morphology is sensitive to a filamentous actin-destabilizing drug, latrunculin-A, and to mutations in the actin-encoding ACT1 gene. Our observations support 1) different mechanisms and cytoskeletal mediators for the inheritance of nuclear and cortical ER elements and 2) a mechanism for cortical ER inheritance that is cytoskeleton dependent but relies on anchorage, not directed movement.

Large-scale identification of genes important for apical growth in Saccharomyces cerevisiae by directed allele replacement technology (DART) screening.

In Saccharomyces cerevisiae, apical bud growth occurs for a brief period in G1 when the deposition of membrane and cell wall is restricted to the tip of the growing bud. To identify genes important for apical bud growth, we have utilized a novel transposon-based mutagenesis system termed DART (Directed Allele Replacement Technology) that allows the rapid transfer of defined insertion alleles into any strain background. A total of 4,810 insertion alleles affecting 1,392 different yeast genes were transferred into a cdc34-2 mutant strain that arrests in the apical growth phase when grown at the restrictive temperature of 37 degrees C. We identified 29 insertion alleles, containing mutations in 17 different genes ( SMY1, SPA2, PAN1, SLA1, SLA2, CBK1, SEC22, FAB1, VPS36, VID22, RAS2, ECM33, OPI3, API1/YDR372c, API2/YDR525w, API3/YKR020w, and API4/YNL051w), which alter the elongated bud morphology of cdc34-2 cells arrested in the apical growth phase. Upon treatment with mating pheromone at 25 degrees C, cells containing insertion alleles affecting ten of these genes ( SMY1, SPA2, PAN1, SLA1, SLA2, CBK1, FAB1, VPS36, VID22, and API2/YDR525w) form abnormal mating projections. Additionally, cells containing insertion alleles affecting SEC22, RAS2, API1/YDR372c, API3/YKR020w,and API4/YNL051display severe mating projection formation defects at the elevated temperature of 37 degrees C. DART mutagenesis has many advantages over traditional mutagenesis methods and will be a useful tool for dissecting gene networks important for biological processes.

Growth and flower initiation in hydrangea as affected by root restriction and defoliation

Effects of container volume and leaf removal on growth and flowering were studied in Hydrangea macrophylla Thunb. ‘Leuchtfeuer’ under conditions conducive to flower initiation. After greenhouse (18°C) conditions for 82 days, container volumes of 140 and 150 cm 3 reduced shoot and root dry weights, numbers of expanded leaves and flower initiation, but increased shoot:root ratio when compared with the plants in 260 and 320 cm 3 pots. After phytotron (14°C) conditions for 50 days, removal of six leaf pairs prevented flower initiation while no defoliation resulted in 100% of plants with flowers initiated. Removal of the upper three expanded leaf pairs increased basal bud size and resulted in 10% of plants with flowers initiated, while removal of the lower three expanded leaf pairs promoted apical bud growth and resulted in 89% of plants with flowers initiated. Reduced flower initiation was associated with both root restriction and defoliation treatments where the dry matter partitioning was changed and numbers of the upper expanded leaves were reduced.

Harvest Time and Nitrogen Source Influence In Vitro Growth of Apical Buds from Fraser Fir Seedlings

Information was obtained concerning appropriate bud harvest time and nitrogen source to be used in the tissue culture of Fraser fir [Abies fraseri (Pursh) Poir] apical buds from 2-year-old seedlings. April was the preferred time to harvest buds for culture, as summer buds had a high contamination frequency, and fall and winter buds did not develop well. Shoot elongation of buds collected in April (1.6 cm) was more than twice that of buds collected in February (0.7 cm) after 100 days in culture; during the same period, shoot fresh mass increased 5-fold (0.21 g in April, 0.04 g in February). Inclusion of a nitrate source reduced the frequency of bud browning, and glutamine was superior to ammonium as a source of reduced nitrogen. Litvay's basal medium containing 10 mm glutamine and 10 mm nitrate was the best nitrogen source combination tested when considering bud browning frequency and shoot fresh mass and length after 100 days in culture.

The Control of Apical Bud Growth and Senescence by Auxin and Gibberellin in Genetic Lines of Peas.

Pea (Pisum sativum L.) lines G2 (dwarf) and NGB1769 (tall) (Sn Hr) produce flowers and fruit under long (LD) or short (SD) days, but senesce only under LD. Endogenous gibberellin (GA) levels were inversely correlated with photoperiod (over 9-18 h) and senescence: GA20 was 3-fold and GA1 was 10- to 11-fold higher in flowering SD G2 shoots, and the vegetative tissues within the SD apical bud contained 4-fold higher levels of GA20, as compared with the LD tissues. Prefloral G2 plants under both photoperiods had GA1 and GA20 levels similar to the flowering plants under LD. Levels of indole-3-acetic acid (IAA) were similar in G2 shoots in LD or SD; SD apical bud vegetative tissues had a slightly higher IAA content. Young floral buds from LD plants had twice as much IAA as under SD. In NGB1769 shoots GA1 decreased after flower initiation only under LD, which correlated with the decreased growth potential. We suggest that the higher GA1 content of G2 and NGB1769 plants under SD conditions is responsible for the extended vegetative growth and continued meristematic activity in the shoot apex. This and the increased IAA level of LD floral buds may play a role in the regulation of nutrient partitioning, since more photosynthate partitions of reproductive tissue under LD conditions, and the rate of reproductive development in LD peas is faster than under SD.