Lateral Shoot Growth Research Articles

The Method of ABA Application Affects Salt Stress Responses in Resistant and Sensitive Potato Lines

The phytohormone abscisic acid (ABA) has been proposed to act as a mediator in plant responses to a range of stresses, including salt stress. Most studies of ABA response apply ABA as a single dose. This may not resemble the prolonged increasing endogenous ABA levels that can occur in association with slowly increasing salinity stresses in nature or field situations. Salt stress response based on method of ABA application was examined in four potato genotypes of varying salt stress resistance: the sensitive ABA-deficient mutant and its normal sibling, a resistant genotype line 9506, and commercial cultivar ‘Norland’ of moderate resistance. ABA was applied by root drench at 0, 50, 75, or 100 μM concentrations through a single dose, or by slowly increasing multiple ABA doses in a sand-based growing system under greenhouse conditions. Salt tolerance was then evaluated after 2 weeks of exposure to 150–180 mM NaCl stress. The method of ABA application had a marked effect on the responses to salt stress. Plant responses to the method of ABA application were differentiated according to (1) growth rate, (2) root water content, and (3) apparent shoot growth response. Under a single dose, growth rate increased in all genotypes under salt stress, whereas slowly increasing multiple ABA applications generally maintained stable growth rates except in the ABA-deficient mutant where there was an upward growth trend. Percent root water content was elevated only under slowly increasing multiple ABA doses in two genotypes, whereas none of the single-dose treatments induced any change. The single ABA dose enhanced vertical growth, whereas the slowly increasing multiple ABA dose applications enhanced lateral shoot growth. Because exogenous application is still an artificial system, endogenous ABA was supplied through grafting of ABA-deficient mutant scions onto rootstocks with known elevated ABA levels. Multiple exogenous ABA applications as low as 50 μM elicited similar shoot water content responses as grafting treatments without ABA application in the mutant genotype but had no effect on the ABA normal sibling. Shoot dry weight was significantly increased through grafting over all exogenous ABA treatments. Our study further indicates that the method of ABA application regime in itself can alter plant responses under salt stress and that certain application regimes may reflect responses to elevated endogenous levels of ABA.

Comparative study of heirloom tomato varieties

The study examined the health status, growth type, berry morphology, berry quality, and gastronomical value of 60 heirloom tomato lines. In the middle of June, the level of virus infection was medium in the plant stock according to the assessments. 21% of the lines did not show symptoms of virus infection. During the vegetation period, the major fungal diseases were Alternaria by the middle of August and Phytophthora from the beginning of September. In spite of the fact that no fungicides were applied, 13% of the lines were healthy and 36% showed medium infection at the end of August. Half of the lines had a strong, 23% of the lines had a medium growth vigour. The majority (74%) of the lines showed strong or medium lateral shoot growth and only 7% of them proved to be less prone to branching. In spite of the rapid growth, 20% of the lines had a weak main stem, the majority of the lines had a main stem medium strength. The different shapes occurred in different colours, in addition to the traditional red colour (53%), there were orange, yellow, wine-red (blackish), lilac, green, almost white or multicoloured varieties. Unfortunately, most of the lines were prone to longitudinal or circular cracking of the berries. Based on the first experiences, all tested variety types had more favourable utilization characteristics then the traditional tomatoes. Varieties with a thick flesh and harmonic acid/sugar ratio such as some of the ox-heart varieties are especially valuable. For drying, the elongated types proved to be the best. The hollow tomato is the most special type which can be utilized most diversely. It is especially suitable for making white tomato soup and, “Concasse" due to its easily removable placenta rich in jelly materials and its thick flesh. In addition, it can be used for preparing stuffed tomato.

Improving the Efficacy of Cytokinin Applications for Stimulation of Lateral Branch Development in Young Sweet Cherry Trees in the Orchard

Improving lateral branch development in young sweet cherry trees without reliance on pruning is a desirable component of tree training programs, especially for high-density systems. Applications of two proprietary formulations of 6-benzyladenine and gibberellins A4 and A7 (Promalin, Valent Biosciences, Walnut Creek, Calif.; and Perlan, Fine Americas, Walnut Creek, Calif.) to individual buds or intact bark of unpruned sweet cherry central leader shoots at green-tip had little effect on lateral shoot growth from buds or on distribution of new shoot growth along the treated leader shoots. Scoring, nicking, or notching cuts alone also had inconsistent effects on shoot development and distribution. In some trials, bud removal (or disbudding, removing every fourth bud on 1-year-old shoots) produced limited improvement of lateral shoot development and vertical distribution. Combining nicking, notching, scoring, or bark scraping with the application of cytokinin–gibberellic acid solution to the cut area greatly improved both number of shoots developed and the numbers originating from the lower portions of treated leader shoots. Removing the physical barrier to bioregulator product contact with active tissues was a primary factor in improving treatment efficacy.

Growth and Fruit Quality of 'Kyoho' Grapevines Grafted on Autotetraploid Rootstocks

The growth of ‘Kyoho’ (Vitis × labruscana Bailey × V. vinifera L.) grapevines grafted on colchicine-induced autotetraploids of two grape rootstocks, ‘Riparia Gloire de Montpellier’ (‘Gloire’, V. riparia Michx.), and ‘Couderc 3309’ (‘3309’, V. riparia × V. rupestris), was compared with the original diploids. Micro-propagated rootstock and ‘Kyoho’ grapevines were grafted in vitro and rooted. During the rooting and acclimating stage, ‘Kyoho’ grapevines grafted on tetraploids had much shorter shoots and internodes than those grafted on the counterpart diploids. In the nursery period in pots, ‘Kyoho’ grapevines grafted on each tetraploid rootstock also showed weaker growth than those grafted on the corresponding diploid rootstock. After planting in the vineyard, lateral shoot growth after primary shoot-tipping, the trunk cross-sectional area and pruned cane weight of ‘Kyoho’ grapevines grafted on each tetraploid rootstock were also smaller than those grafted on the corresponding diploid rootstock. The berries of ‘Kyoho’ grapevines grafted on tetraploids showed much deeper skin coloration than those of vines grafted on diploid rootstocks.

The Influences of Growth Regulators and Culture Medium Composition on Shoot-Tip Cultures of Edible Canna

Explants obtained from the terminal buds of edible canna (Canna edulis Ker-Gawl.) were aseptically cultured with different combinations of auxins (NAA, IBA), cytokinins (BA, KN, 2ip), and culture media (B5, 1/2MS, MS), to establish a tissue culture system for this species. The combination of NAA or IBA with BA induced optimal explant growth, and when the explants grew substantially, TIBA promoted lateral shoot growth. For explant growth, the optimal concentration of NAA was 0.1∼0.5 mg L-1, irrespective of the BA concentration adopted, and the optimal concentration of BA was 0.5∼1 mg L-1. Some of the explants formed callus-like or protocorm-like tissues. Among the three culture media, B5 gave the highest survival rate of explants (92%), followed by 1/2 MS (72%) and MS (52%). In these combinations, micronutrients followed by macronutrients and vitamins, were found to be most important components for explant survival. Gellan gum at 2.5 g L-1 was a superior supporting/gelling material for explant growth compared to a filter paper-bridge with liquid medium or 4 g L-1 agar. Our results indicate that multiple plantlet propagation can be performed routinely, while callus formation remains a time-consuming endeavor.

Effects of post-harvest regulated deficit irrigation on carbohydrate and nitrogen partitioning, yield quality and vegetative growth of peach trees

The aim of the present work was to evaluate the effects of regulated deficit irrigation (RDI) applied in the post-harvest stage of peach trees. The 3-year trial was carried out in Italy (N 40°20′, E 16°48′) on mature peach plants (cv “Springcrest”) trained to transverse Y. From bud break to harvest, irrigation was carried out by applying 100% ETc, while from harvest to early autumn, plants were separated into three groups and subjected to different irrigation treatments (100, 57 and 34% ETc). The decrease in soil water content caused a reduction in the values of tissue water potential and gas exchange both in 57% ETc and 34% ETc treatments. RDI determined the reduction in the growth of waterspouts and lateral shoots but did not influence the growth of fruiting shoots. During the trial, no significant reductions in crop yield and quality were observed in the 57% ETc treatment, whereas about 1,100, 1,800 and 2,500 m3 ha−1 of water were saved in the first, the second and the third year, respectively. In the second year of the trial, the use of RDI in the post-harvest stage determined carbohydrate and nitrogen accumulation in roots, branches, shoots and floral buds. The results demonstrate that, under scarce water supply conditions, a clear benefit can be obtained through the use of RDI during the post-harvest stage. This confirms the possibility to reduce the irrigation water by applying RDI during phenological stages less sensitive to water deficit without negatively affecting peach growth and yield.

Characterization of three members of the Arabidopsis carotenoid cleavage dioxygenase family demonstrates the divergent roles of this multifunctional enzyme family

Arabidopsis thaliana has nine genes that constitute a family of putative carotenoid cleavage dioxygenases (CCDs). While five members of the family are believed to be involved in synthesis of the phytohormone abscisic acid, the functions of the other four enzymes are less clear. Recently two of the enzymes, CCD7/MAX3 and CCD8/MAX4, have been implicated in synthesis of a novel apocarotenoid hormone that controls lateral shoot growth. Here, we report on the molecular and genetic interactions between CCD1, CCD7/MAX3 and CCD8/MAX4. CCD1 distinguishes itself from other reported CCDs as being the only member not targeted to the plastid. Unlike ccd7/max3 and ccd8/max4, both characterized as having highly branched phenotypes, ccd1 loss-of-function mutants are indistinguishable from wild-type plants. Thus, even though CCD1 has similar enzymatic activity to CCD7/MAX3, it does not have a role in synthesis of the lateral shoot growth inhibitor. Rather, it may have a role in synthesis of apocarotenoid flavor and aroma volatiles, especially in maturing seeds where loss of function leads to significantly higher carotenoid levels.

Slow recovery of heather (Calluna vulgarisL. (Hull)) in Scottish moorland after easing of heavy grazing pressure from red deer (Cervus elaphusL.)

Summary The study aimed to determine how quickly heather responds in Scottish moorland once deer grazing pressure is reduced. We monitored heather attributes and deer distribution over ten years in Glen Lui and Glen Derry, two contrasting nearby areas of it 200 ha at Mar Lodge in the eastern Cairngorms. In one area the deer received winter food, affecting the zonation of their impact. In both areas the deer were initially lightly culled, then culling was increased. Mean heather shoot utilisation was 35 % and 48 % less in the last five years of the study than initially in the two areas, and was very closely correlated with deer pellet-group counts. In Glen Lui heather cover increased significantly but height increases were small. In Glen Derry heather increased significantly in height but little in cover. We attributed the different response to the presence of a secondary grazer (rabbits, Oryctolagus cuniculus) in Glen Lui and also better conditions for heather growth on the drier soils there; rabbits grazemore delicately than deer, taking mainly the shoottips of heather and thus encourage lateral shootgrowth. In Glen Lui heather response also varied between four radial zones based on distance from the feeding grounds. At best, there was appreciable recovery four years after the easing of deer grazing pressure, but average amounts of recovery were modest.

Resistant Rootstocks, Preplant Compost Amendments, Soil Fumigation, and Row Repositioning for Managing Apple Replant Disease

We are testing control tactics for apple replant disease (ARD) complex, a worldwide problem for fruit growers that is attributed to various biotic and abiotic soil factors. In Nov. 2001, “Empire” apple trees on five rootstocks (M.26, M.7, G.16, CG.6210, and G.30) were planted into four preplant soil treatments—commercial compost at 492 kg/ha soil-incorporated and 492 kg·ha-1 surface-applied), soil fumigation with Telone C-17 (400 L·ha-1 of 1,3-dichloropropene + chloropicrin injected at 30 cm depth five weeks prior to replanting), compost plus fumigant combination, and untreated controls—at an old orchard site in Ithaca, N.Y. Trees were replanted in rows perpendicular to, and either in or out of, previous orchard rows. Irrigation was applied as needed, and N-P-K fertilizer was applied in 2001 to all non-compost treatments to compensate for nutrients in the compost treatment. After two growing seasons, the rootstock factor has contributed most to tree-growth differences. CG.6210 rootstock supported greater growth in trunk diameter, central leader height, and lateral shoot growth (P < 0.05), regardless of preplant soil treatments and replant position. Trees on M.26 grew least over a two year period. Replant growth was greater in old grass lanes than in old tree rows, despite higher root-lesion nematode populations in previous grass lanes. Growth responses to preplant soil fumigation were negligible. Preplant compost did not increase tree growth during year one, but did increase lateral branch growth in year two. Results thus far suggest that replanting apple trees out of the old tree-row locations, and using ARD tolerant rootstocks such as CG.6210, may be more effective than soil fumigation for control of ARD in some old orchard sites.

Early growth of Brazilian pine (Araucaria angustifolia[Bertol.] Kuntze) in response to soil compaction and drought

Soil compaction leads to changes in soil physical properties such as density, penetration resistance and porosity, and, by consequence, affects root and plant growth. The initial growth of Brazilian pine is considered as being more affected by soil physical than chemical conditions, and the presence of a well-developed tap root system has been associated with this fact. A greenhouse experiment was conducted in order to evaluate the impact of soil compaction on the growth of Brazilian pine seedlings and on their susceptibility to a simulated drought period. In the first phase of the experiment, the effects of three levels of soil compaction on root morphology and plant growth were examined. Soil cylinders were artificially compacted in PVC tubes. Pre-germinated seeds were planted, and 147 days later 10 plants from each treatment were harvested for analysis. Higher values of soil density were associated with a shorter and thicker tap root. Growth of lateral roots and shoots remained unaffected at this stage. In the second phase, half of the plants (12) in each compaction treatment were drought-stressed by withholding water for a period of 77 days. Increased soil compaction again resulted in reduced length and increased diameter of the main tap root. This time, the effects were also extended to the lateral roots. Shoot extension growth and overall plant mass, however, increased with soil compaction. This greater mass accumulation in plants growing under increased soil compaction may be attributed to a more intimate contact between roots and soil particles. Drought stress reduced both root and shoot growth, but root mass was more negatively affected by drought stress in plants growing under high levels of soil compaction. Future investigations on the effects of soil compaction on the initial growth of Brazilian pine should include a wider range of compaction levels to better establish the relationship between soil physical parameters and plant growth.

Comparative effects of four plant growth retardants on growth of Epidendrum radicans

SummaryThe effect of paclobutrazol, triapenthenol, daminozide and chlormequat chloride on the growth of Epidendrum radicans was studied over one year. Paclobutrazol and triapenthenol were applied as soil drenches at 5, 10 and 20 mg –1, while 1000, 2000 and 4000 mg l–1 daminozide and 2000, 4000 and 6000 mg l–1 chlormequat chloride were applied as foliar sprays. Main and lateral shoot growth restriction (54-75%) was obtained by all doses of paclobutrazol and 20 and 10 mg l–1 triapenthenol. Daminozide at 4000 and 2000 mg l–1 restricted only main shoot growth. Chlormequat chloride at 6000 mg –1 had a similar effect but caused leaf toxicity symptoms, as white spots. The effect of the four growth retardants on shoot growth restriction followed the order paclobutrazol>triapenthenol> daminozide>chlormequat chloride. The number of lateral shoots developed during the treatment period and the main and lateral shoot diameter were not affected by any chemical used. Leaf length was much reduced (46-62%) by all doses of paclobutrazol and the two higher doses of triapenthenol and to a lesser extent (13-29%) by all doses of daminozide and the lower dose of triapenthenol, while it was not affected by chlormequat chloride. Leaf width was restricted (13-37%) by the two higher doses of paclobutrazol, triapenthenol and daminozide and the highest dose of chlormequat chloride. Leaf thickness was much increased (52-76%) by all doses of paclobutrazol and the two higher doses of triapenthenol. The lower dose of triapenthenol and daminozide, and all doses of chlormequat chloride, caused a smaller increase in leaf thickness (17-37%). Seven and a half months after the end of treatments paclobutrazol was the most persistent of the growth retardants used. For compact E. radicans pot plants, without special needs of support, a 10 mg l–1 paclobutrazol soil drench applied monthly is recommended.

A Preliminary Investigation on Partial Rootzone Drying (PRD) Effects on Grapevine Performance, Nitrogen Assimilation and Berry Composition

Partial rootzone drying (PRD) is an irrigation management technique designed to reduce water use in grapevines without a decline in yield, thereby increasing water use efficiency (WUE). Experiments consisted of field-grown Cabernet Sauvignon, where the PRD grapevines were irrigated with half the amount of water as control grapevines, and Shiraz, where the PRD grapevines received the same amount of water as control grapevines. PRD treatments showed no significant differences in yield or berry composition at harvest, except that PRD grapevines that received half the amount of water had significantly smaller berries than control grapevines. Cabernet Sauvignon PRD grapevines receiving half the amount of water as control grapevines showed a 34 % reduction in main shoot growth and up to a 74% reduction in lateral shoot growth. Shoot growth was inhibited to a lesser extent in Shiraz PRD grapevines receiving the same amount of water, with a 20% reduction in main shoot.growth and a 33% reduction in lateral shoot growth. PRD also significantly reduced stomatal conductance in Cabernet Sauvignon on average by 31 % and 16% in Shiraz. Nitrate reductase (NR) activity in grapevine leaves was significantly lowered in response to PRD, irrespective of the amount of water applied. The reduction in NR activity was closely correlated with the development of the PRD cycle and the associated reduction in stomatal conductance.

Seasonal development of annual shoots in some terrestrial orchids from Russia and Japan

AbstractAnnual shoots of 46 terrestrial orchid species commonly found in wide ranges of temperate climates in Russia and Japan change their patterns of growth recurrence from the dormancy state, through formation and growth, to the next dormancy state during the course of yearly response to seasonal cycles of environmental conditions. Each of the species has its own strategy in seasonal development of aerial shoots, rhizomes, tubers and roots, and shows seasonal differentiation of shoot morphogenesis at the early stage of new shoot apex formation in accordance with its growth habit, habitat and range size of geographical distribution. Perennial orchids with sympodial growth patterns and primitive life forms are characterized by long duration of shoot and inflorescence development inside the bud. Among the species studied, the orchids that have annually regenerating root‐stem tubers have the shortest duration of root and shoot morphogenesis. The species that have predominant patterns of monopodial growth show variability in duration of lateral shoot growth due to the energy budget of the mother plant. The species which have latitudinally long ranges of distribution from northern colder regions to southern warmer regions tend to take longer for shoot development inside the bud, and aerial shoots have a shorter life‐span in the northern regions than those in the south.

Stimulatory effect of cytokinins and interaction with IAA on the release of lateral buds of pea plants from apical dominance

Lateral buds of pea plants can be released from apical dominance and even be transformed into dominant shoots when repeatedly treated with synthetic exogenous cytokinins (CKs). The mechanism of the effect of CKs, however, is not clear. The results in this work showed that the stimulatory effects of CKs on the growth of lateral buds and the increase in their fresh weights in pea plants depended on the structure and concentration of the CKs used. The effect of N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU) was stronger than that of 6-benzylaminopurine (6-BA). Indoleacetic acid (IAA) concentration in shoot, IAA export out of the treated apex and basipetal transport in stems were markedly increased after the application of CPPU or 6-BA to the apex or the second node of pea plant. This increase was positively correlated with the increased concentration of the applied CKs. These results suggest that the increased IAA synthesis and export induced by CKs application might be responsible for the growth of lateral shoots in intact pea plants.

Effects of fruit load on partitioning of [formula omitted] and [formula omitted], respiration, and growth of grapevine roots at different fruit stages

The effects of different fruit loads on the root activity and growth of roots and shoots in large potted grapevines ( Vitis labruscana, var. Aki-queen) were investigated, heavy fruit load (HFL, two bunches per new bearing shoot), medium fruit load (MFL, one bunch per new bearing shoot, which was the standard fruit load), and no fruit load (NFL), in an unheated greenhouse at three growth stages: berries enlarging (June), veraison (July), and pre-harvest (August) were compared. A liquid oxygen electrode method was used to determine root activity from the absorption of 15 N (as ammonium sulfate), the partitioning percentage of 15 N in the roots, and the respiration of fine roots. We also examined the 13 C -photoassimilate partitioning and absorption percentages in whole plants. HFL and MFL grapevines had a lighter dry mass of fine roots (17–19%) and shoots at all stages than NFL grapevines. NFL grapevines had the highest dry mass percentage in fine roots (24%). HFL reduced lateral shoot growth and reduced rooting production of new fine roots. Although the total sugar accumulation per vine was the highest in the HFL grapevines, sugar accumulation per berry was lower in the HFL vines than in the MFL vines. The fresh weight of both bunches and berries and the sugar content of berries were significantly decreased by heavier fruit loads at harvest in late August. The respiration rate of the fine roots of NFL grapevines (about 8 μmol O 2 g FW −1 h −1) was higher than those of HFL and MFL grapevines (between 4 and 6 μmol O 2 g FW −1 h −1) at all stages of fruit growth. From roots, 15 N partitioning was highest in the fine roots. Among treatments, the partitioning percentage in the fine roots was highest in the NFL grapevines (between 20 and 40%) compared with MFL and HFL vines (about 15%) at all three stages. 15 N assimilated per unit dry mass of the NFL fine roots was the highest in July and August. During veraison, the fruit of the HFL and MFL grapevines received the highest partitioning percentage of 13 C -photoassimilates, and the fine roots and trunks of the NFL grapevines received the highest percentages. Among roots, the fine roots received the highest percentage in all treatments at all stages. The fine roots of the NFL grapevines received a higher 13 C -photoassimilate percentage (13–14%) than those of the HFL (4–8%) and MFL (6–7%) grapevines throughout the experiment. These results demonstrate that root activity and vegetative growth were strongly affected by fruit load and that a heavy crop load forced vines to accumulate less sugar in the roots and shoots. This means that fruit has priority in the accumulation of photoassimilates and partitioning nitrogen.

Effects of light availability on growth, architecture and nutrient content of the seagrass Zostera noltii Hornem

The growth vs. irradiance response of the seagrass Zostera noltii from Cadiz Bay Natural Park (southwestern Spain) was characterised. Plants were exposed along 14 days to different light treatments (1%, 7%, 42% and 100% surface irradiance, SI), using shade screens in an outdoor mesocosm. Growth at 100% SI (1.6 mg DW plant −1 day −1) was lower than that at 42% SI (2.4 mg DW plant −1 day −1), suggesting photoinhibition. The minimum light requirement estimated was 0.8 mol photons m −2 day −1 (2% SI). Light availability affected the pattern of plant development and the overall plant growth. The contribution of the apical shoots to the aboveground production was nearly constant (c.a. 1.13 cm plant −1 day −1) regardless of the light level (except at 1% SI). In contrast, recruitment and growth of lateral shoots arising from the main rhizome axes accounted for the observed differences in aboveground growth. Rhizome branching was only observed at 42% SI. The possibility of a light threshold for rhizome branching could explain the seasonality of shoot recruitment, as well as the observed decrease in shoot density along depth (or light) gradients in seagrass meadows. Carbon demands at low irradiances (1% and 7% SI) were partially met by mobilization of carbohydrate reserves (sucrose in belowground and starch in aboveground parts). Plant nitrogen content decreased with increasing light, especially in belowground parts, reaching critical levels for growth.

Hormone physiology of pea mutants prevented from flowering by mutations gi or veg1.

The veg1 (vegetative) mutant in pea (Pisum sativum L.) does not flower under any circumstances and gi (gigas) mutants remain vegetative under certain conditions. gi plants are deficient in production of floral stimulus, whereas veg1 plants lack a response to floral stimulus. During long days in particular, these non-flowering mutant plants eventually enter a stable compact phase characterised by a large reduction in internode length, small leaves and growth of lateral shoots from the upper-stem (aerial) nodes. The first-order laterals in turn produce second-order laterals and so on in a reiterative pattern. The apical bud is reduced in size but continues active growth. Endogenous hormone measurements and gibberellin application studies with gi-1, gi-2 and veg1 plants indicate that a reduction in gibberellin and perhaps indole-3-acetic acid level may account, at least partially, for the compact aerial shoot phenotype. In the gi-1 mutant, the compact phenotype is rescued by transfer from a 24- to an 8-h photoperiod. We propose that in plants where flowering is prevented by a lack of floral stimulus or an inability to respond, the large reduction in photoperiod gene activity during long days may lead to a reduction in apical sink strength that is manifest in an altered hormone profile and weak apical dominance.

Soil nitrogen utilisation for growth and gas exchange by grapevines in response to nitrogen supply and rootstock

This study investigated the response to nitrogen (0 or 100 kg N/ha) of field-grown Muller-Thurgau grapevines grafted on six rootstocks (Kober 5BB, Teleki 5C, Teleki 8B, Selection Oppenheim 4, Couderc 3309, Ruggeri 140). Half the nitrogen was applied four weeks pre-flowering and half at the end of flowering. Glutamine accounted for over 85% of xylem nitrogen, indicating that most soil nitrogen was assimilated by way of vine root metabolism. Nitrogen supply increased the translocation of glutamine, glutamate, NO3-, NH4+, K+, Ca2+, Mg2+ and PO43- in the xylem sap and decreased the ratio of organic to inorganic nitrogen. V. berlandieri ¥ V. riparia crosses generally resulted in higher xylem solute concentrations compared with other rootstocks, but were less effective in total nitrogen assimilation. High soil nitrogen increased vine leaf area by stimulating lateral-shoot growth, increased leaf chlorophyll, photosynthesis, transpiration and stomatal conductance, and delayed leaf senescence. There was no difference among rootstocks in scion leaf area, but rootstocks affected scion response to soil nitrogen level in terms of leaf chlorophyll content and leaf gas exchange; SO4 induced the strongest reaction to soil N, whereas Ru-140 elicited the least reaction. Chlorophyll content was highest for vines grafted on 5BB and lowest for C-3309. Photosynthesis response to both nitrogen and rootstock was regulated at the mesophyll level. There were few interactions between nitrogen and rootstocks, and their contribution to total variance was small relative to main effects. Thus, with the exception of SO4, differences due to rootstocks were mostly unaffected by soil nitrogen level.

Genotype of Apple Trees Affects Growth and Fruiting Responses to Shoot Bending at Various Times of Year

Growing shoots of two apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] genotypes differing in shoot architecture, the preselection X.3318 and the cultivar `Chantecler', were bent on three dates during the summer and one in the winter to evaluate the interactive effects of shoot architecture and bending date on lateral shoot development and growth over 3 years. Bending X.3318, with a high proportion of vegetative lateral shoots on 1-year-old wood, on different dates did not change the percentage of lateral budbreak (62% to 65%). However, bending in June or July increased lateral growth on 1- and 2-year-old wood in a mesotonic position, whereas bending in winter reduced lateral growth and redistributed the shoots more basitonically. Both number and weight of fruits were reduced by bending. In `Chantecler', which forms many flower buds on 1-year-old wood, bending during flower bud formation (June-July) increased the percentage of lateral budbreak (60% vs. 45% for the control) and the number of flower buds. After 3 years of development, early summer treatments reduced the abortion of laterals as compared to the control. As a consequence, bending increased the number, as well as the weight of fruit. These results show that the effects of bending on the development and growth patterns of lateral shoots vary with genotype.

Responses of eelgrass Zostera marina seedlings to reduced light

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 223:133-141 (2001) - doi:10.3354/meps223133 Responses of eelgrass Zostera marina seedlings to reduced light Joanne C. Bintz1,*, Scott W. Nixon2 1Ocean Studies Board, National Academy of Sciences, 2101 Consitution Av. NW, HA 470, Washington, DC 2041, USA 2Graduate School of Oceanography, University of Rhode Island, PO Box 200, South Ferry Road, Narragansett, Rhode Island 02882, USA *E-mail: jbintz@nas.edu ABSTRACT: We subjected seedlings of Zostera marina L. to High (72%), Medium (23%), and Low (10%) daily irradiance (mean daily PAR of 24.4, 7.9, and 3.3 E m-2 d-1 respectively) over 12 wk. We measured plant response in terms of survivorship, lateral shoot production, morphology, growth rate, photosynthesis and respiration, and leaf pigment concentration. Decreasing the light available to eelgrass seedlings from 72 to 23% resulted in a reduction of lateral shoot formation, lower plant biomass, and longer and wider leaves. Shoot area, growth rate, and pigment concentrations remained similar. A reduction of incident light to 10% decreased survival to 74% and had a negative effect on shoot growth, size, and above- and belowground biomass. Pigment concentrations increased with respect to seedlings raised at medium light. In general, the responses of seedlings to reduced light are similar to those reported for mature Z. marina. Rapid expansion of seedling patches can only occur at irradiance levels greater than 7.9 E m-2 d-1. Morphological changes resulting from exposure to mean daily PAR levels of less than 8 E m-2 d-1 such as thinner leaves and low belowground biomass, have serious implications for decreased seedling survival in the field. KEY WORDS: Eelgrass · Seagrass seedlings · Light · Zostera marina · Shade adaptation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 223. Online publication date: November 28, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.