Rhizome Production Research Articles

Long-term effect of beach replenishment on natural recovery of shallow Posidonia oceanica meadows

The recovery capacity of shallow Posidonia oceanica meadows degraded by beach replenishment eighteen years before was assessed in two impacted meadows and compared with other two undisturbed localities. Inside each locality, we selected randomly three sites separated by 500–1000 m. At site level we study the vitality of P. oceanica meadow assessing the vegetative growth, leaf characteristics, and non-structural carbohydrates of the plants. Additionally, at locality level, silt-clay fraction, organic matter, pH and light intensity incident on the sea bottom were measured to evaluate the environmental conditions. Covering of P. oceanica was significantly lower at the impacted localities while amount of dead “matte” was higher. Leaf production of horizontal rhizomes (14.6 ± 1.11 vs 19.47 ± 1.45 leaves y −1), net total rhizomes recruitment (2.33 ± 0.17 vs 4.3 ± 0.33 branches y −1) and starch concentration (43.625 ± 0.67 vs 54.45 ± 0.74 mg per g of rhizome) at impacted meadows were significantly lower than controls. Leaf features, epiphytes biomass, colonization, elongation and horizontal and vertical rhizome production did not show significant differences. Sediments at impacted localities contained higher silt-clay fraction and higher organic matter load while pH was lower. Light intensity on the sea bottom measured at all localities was over the minimum light requirements estimated for P. oceanica. Our results show that the press impact produced by beach replenishment was enduring in the time slowing natural recovery by 45%. This impact may be related with changes in the sediment features.

Nitrogen cycling dynamics in the carnivorous northern pitcher plant, Sarracenia purpurea

Summary 1In nutrient-poor environments, plants employ many strategies to acquire and recycle scarce nutrients. Predictable relationships among a variety of leaf traits, including leaf nitrogen (N) suggest that how plants obtain, use, store and re-use N is a major component of plant fitness. The northern pitcher plant, Sarracenia purpurea, receives nitrogen from multiple sources: NH4 and NO3 dissolved in precipitation; N mineralized from captured prey; the scant N in saturated peat; and N remobilized from storage. In two greenhouse experiments, we examined N cycling in S. purpurea and consider how these dynamics relate to prior observations that this carnivorous plant has an unusually low photosynthetic rate for its tissue N content. 2In the first experiment we assessed assimilation, translocation, storage and remobilization of 15N supplied to pitchers and roots. In the second experiment, we examined how 15N assimilated by the first pitcher produced at the start of the growing season contributed to the production and maintenance of subsequent pitchers, roots and rhizomes. 3Patterns of N cycling were similar at the individual-leaf and whole-plant level. Pitchers assimilated 55%–69% of available 15N and served as both the largest sink for newly assimilated N (> 90% of the 15N assimilated during 2004) and the largest source of N remobilization the following spring. In contrast, N assimilated by roots was low and accounted for < 2·5% of the overall S. purpurea N budget. Sarracenia purpurea used both stored N and newly-acquired N throughout the growing season. The importance of stored N decreased throughout the growing season as newly assimilated N contributed more to later pitcher production. 4Our detailed mechanistic analysis of nitrogen cycling dynamics of S. purpurea suggests why this plant has a low photosynthetic rate for its tissue N content. Excess nitrogen is stored for future use, and production of new pitchers is primarily aimed at enhancing prey capture rather than increasing photosynthetic tissue.

Response of a Gibberellin-deficient Potato Mutant to Induction and Growth Regulators as a Working Model for Tuber Initiation

To explore further the role endogenous gibberellins play in the formation of the potato tuber, a gibberellin-deficient dwarf of Solanum tuberosum subsp. andigena (PI 281036) and its normal sibling were used in this study. Because gibberellins are known to be elevated and to affect tuber formation negatively when potato plants are grown under long day conditions, test plants were first grown in a growth chamber under conditions that did not favor tuberization (noninducing conditions). The stem apices of dwarfs received weekly applications of a 100-ppm gibberellic acid (GA3) solution to achieve growth similar to that of normal plants. When the requisite height was achieved, five dwarfs and five normal sibs were treated to foliar runoff with a 100-ppm GA3 solution, and a like number of these plants received a control spray of distilled water. These plants were then placed in a growth chamber adjusted to inducing conditions for tuber initiation. An additional five dwarfs and five normal sibs were sprayed with 600 ppm paclobutrazol (PB), a gibberellin inhibitor, and a similar number of plants received a distilled water control spray. This group of plants was returned to the noninducing chamber. After 1 week, plants were removed from their respective growth chambers and divided into two-node apical, medial, and basal leaf-bud cuttings. Basal buds of the cuttings were buried in moist potting mix in a mist chamber with a 16-hour photoperiod. Rhizome and tuberization responses were evaluated after 3 weeks. The experiment was repeated and results combined for statistical treatment. Orthogonal contrasts revealed that apical cuttings from normal donor plants produced rhizomes only under noninducing conditions or when treated with GA3. No rhizomes formed on apical cuttings from normal plants growing under inducing conditions (favoring tuberization) or noninduced plants receiving PB (a gibberellin inhibitor). For apical dwarf tissues, there were no effects of treatments on rhizome production, except for the PB treatment, which resulted in shorter rhizomes. Tuberization was observed in apical tissues of induced and noninduced dwarfs, which lack the ability to synthesize gibberellin, but only in induced cuttings of normal sibs. Noninduced dwarf cuttings tuberized as well as those from normal plants receiving the antigibberellin treatment. Tuber weights from induced apical cuttings of dwarfs and normal sibs were not significantly different. These results support the significant role played by gibberellins in tuber formation.

Effects of light and biomass partitioning on growth, photosynthesis and carbohydrate content of the seagrass Zostera noltii Hornem

Plants of the seagrass Zostera noltii were cultured in the laboratory (mesocosms) for two weeks to assess the effect of above:below-ground (AG/BG) biomass ratios and light on growth, photosynthesis and chemical composition. Experimental plant units (EPUs) with different proportions between AG and BG biomass were obtained from plants of the same size (containing 6 shoots and 5 internodes) by excising 0–5 shoots. The EPUs maintained the proportions in AG/BG biomass ratios during the experiment. While growth rate was unaffected by biomass partitioning at high light, maximum growth at low light was recorded in plants with low AG/BG ratios. The production of shoots and rhizomes showed a compensatory morphological response depending on the initial AG/BG proportions regardless of the light level. While shoot production, estimated as shoot appearance rate, was high at low AG/BG ratios and minimal under high AG/BG values, rhizome production, estimated as internode appearance rate and internode elongation rate, was maximal under high AG/BG proportions and decreased towards lower AG/BG ratios. This rhizomatic response was observed for secondary rhizomes and not for primary ones. In contrast to morphological response, no significant differences were detected in maximum electron transport rates (ETRm) among the different shoots in the plant. However, mean values of ETRm in plants were affected by biomass partitioning and light. EPUs grown in low light increased the sucrose stored in shoots as the AG/BG biomass ratios decreased; however, EPUs grown at high light showed no effect of biomass partitioning on sucrose levels. In conclusion, shoots excision by experimental manipulation caused a compensatory morphological response in plants while photosynthetic performance remained almost unaffected.

Growth and productivity of intertidal Zostera capricorni in New Zealand estuaries

In situ leaf and rhizome growth and productivity rates were determined for intertidal populations of Zostera capricorni in three New Zealand estuaries on four occasions in summer and winter 2000 and 2001. Leaf growth and productivity, leaf plastochrone interval, leaf life‐spans and turnover rates were found to vary depending on site, bed position, season, and year. Absolute leaf growth (2.1±0.8mm leaf‐1 day‐1) and productivity (0.4+0.2 mg shooir‐1 day‐1) were generally lowest, relative growth (0.2±0.6mm leaf‐1 day‐1) and productivity (0.4±0.4 mg shoot‐1 day‐1) highest, and the leaf and shoot plastochrone intervals shorter at the site exposed to greater desiccation stress and photoinhibitory high irradiances. Rhizome growth rates, the production of new branches and shoots, as well as rhizome and shoot plastochrone intervals were also found to vary depending on site, season, and year. The results indicate that Z. capricorni is able to maintain high productivity and growth rates in intertidal estuarine environments which signify a high degree of environmental stress for marine plants.

Weed Control Potential and Crop Safety of Selected Herbicides in Field-grown Cannas

Herbicides were applied pre-emergence (PRE) and early post-directed (EP-DIR) to determine their effects on crop injury and control of palmer amaranth (Amaranthus palmeri) and nutsedge (Cyperus spp.) in field-grown cannas (Canna ×generalis). Results indicate that PRE-applied s-metolachlor + pendimethalin was the most effective treatment for controlling palmer amaranth. All other PRE-applied treatments failed to adequately control palmer amaranth. While moderate and temporary stunting was visible, in general, no herbicides (except trifloxysulfuron) significantly decreased canna rhizome yields. EP-DIR s-metolachlor or s-metolachlor + pendimethalin did not improve nutsedge control unless halosulfuron was included in the tank mixture. Addition of halosulfuron did not increase crop injury or decrease canna yields but did significantly reduce the number of nutsedge tubers found in the canna rhizomes at harvest. Results suggest that all PRE-applied herbicides tested were safe for cannas, but the lack of adequate palmer amaranth and nutsedge control prohibits their use as stand-alone herbicides for canna production in the midsouth. Post-directing applications of halosulfuron significantly improved nutsedge control and reduced tuber infestation and, therefore, should be included in all nutsedge management programs for canna rhizome production.

Modelling the relationship between sexual reproduction and rhizome growth inPosidonia oceanica(L.) Delile

AbstractThe relationship between flowering and growth performance ofPosidonia oceanica(L.) Delile in meadows distributed along the south‐eastern coast of Sicily (Italy) was investigated by means of a statistical model (generalized linear mixed model) combined with the lepidochronological analysis. Over a 28‐year period, 67 floral stalk remains were observed. The highest flowering index was recorded in lepidochronological year 1998 (10.1%) and the Inflorescence Frequency per age showed a clear decrease corresponding to 15‐year‐old shoots. The sexual reproductive event had positive effects on rhizome elongation (cm year−1) and leaf production (no. leaves year−1) in the same flowering year, whilst no effect on the rhizome production (mg year−1) was observed. Rhizome growth variables showed significant negative lagged responses in the two years following flowering. On the whole, we calculated that the effect exerted by flowering, in terms of loss on rhizome elongation and production, was about 27% and 38%, respectively. Although it has been demonstrated that recovery from the stress induced by sexual reproduction is limited to the two years after flowering, the magnitude of the reproductive cost may become quite considerable especially in comparison with the whole lifespan of individual shoots.

Conservation ecology of endangered species Paphiopedilum armeniacum (Orchidaceae)

Paphiopedilum armeniacum is an endangered orchid species, endemic to China. During the period of April 2000 to October 2005, 66 observation sites were selected in Luoshapo of Nushan Mountains in Yunnan, China, to carry out the conservation ecological research on P. armeniacum. A total of 443 genets (1302 ramets in total) of P. armeniacum were sampled, their biological characteristics such as reproductive pattern, phenology, and life cycle were observed, and the ecological habits of the species such as the habitat and the structure of communities were studied. Experiments on ex-situ conservation were conducted, and the cloned ramets were replanted to their original habitat after ex-situ reproduction in Shenzhen, Guangdong, China. The relationships between P. armeniacum and climate, vegetation, other environmental factors in the original habitat, and the biological characteristics of asexual offsprings of P. armeniacum, which were replanted to the original habitat after ex-situ cultivation and reproduction, were investigated. The studies show that P. armeniacum in Luoshapo grows very well in secondary shrub boskets or in tussocks on limestone hills. It has both sexual and asexual reproduction. Asexual reproduction serves to complete the sexual reproduction and to extend the lifetime of genets, while it does not reduce sexual reproduction. There are two modes of asexual reproduction-by tillering or by producing rhizomes. The litter of shrub boskets or tussocks provides P. armeniacum with humus, and the rhizome reproduction of P. armeniacum is an adaptation to the litter-covered condition, i.e. to escape from the unfavorable environment. Blooming rate of ramets is 7.39% ± 1.02%, and fruit set rate from the blooming ramets is 32.23% ± 12.08%. P. armeniacum is able to invade the moderately destroyed forests and those in early restoring but is unable to grow in large dense forests. P. armeniacum also grows very well in artificial spare woods in Shenzhen and can reproduce many cloned ramets, which can normally bloom and yield fruits after being replanted to the original habitat. The results of this study show that P. armeniacum can be conserved by ex-situ conservation and by replanting the ex-situ reproduced ramets to original habitat. On the basis of the analysis of endangered mechanisms of P. armeniacum, it can be concluded that P. armeniacum has strong capability of both asexual and sexual reproductions, and an emergency mechanism consisted of massive production of rhizomes to cope with damage. Because highly effective pollinating insects that facilitate pollination in P. armeniacum are present in the habitat, flowering ramets produce fruits with large quantity of seeds, many of which in turn grow into new genets that can reproduce many cloned ramets. P. armeniacum makes very effective use of its environment and has distinct characteristics of enduring harsh environmental conditions; therefore, rather than its own inherent biological defects, the main threats facing this species are the destruction of its survival space and the wipe-out collecting of the plants as a result of trading. Based on the analysis mentioned above, certain appropriate strategies have been proposed for the conservation of P. armeniacum.

Influence of propagation method a nd indole-3-butyric acid on growth and development of in vitro- and ex vitro-derived lingonberry plants

The effects of two propagation methods and four indole-3-butyric acid (IBA) concentrations were studied in two cultivars of lingonberry (Vaccinium vitis-idaea L.). Cultivars Regal and Erntedank, propagated by conventional softwood cuttings (SC) and adventitious shoot regeneration from excised leaves of micropropagated shoots (LC), were evaluated for growth and morphology. Significant two- and three-way interactions for shoot and rhizome characteristics were observed among the treatments. The LC plants produced shorter and less-vigorous shoots but had more stems, branches, leaves and rhizomes in contrast to conventional cuttings, which rarely produced rhizomes. IBA had an effect on shoot and rhizome morphology, but not on the frequency of rhizome formation. In vitro culture on zeatin-containing nutrient medium apparently induces the juvenile branching characteristics that favored enhanced rhizome production. The advantage of shoot and rhizome production of adventitiously produced LC plants over SC plants varied between the genotypes. Erntedank plants had better shoot growth and rhizome development across propagation methods than did Regal plants. Key words: Vaccinium vitis-idaea, propagation, regeneration, cuttings, indole-3-butyric acid

Genetic divergence among Curcuma longa L. accessions

The genetic divergence among 21 turmeric genotypes was evaluated based on morpho-agronomical traits and on multivariate procedures in order to select divergent top-yielding genotypes. The experiment was carried out from 2001/ 2003 in randomized block design with four replications. Six descriptors describing rhizome production and curcuminoid content were evaluated. From Mahalanobis' distance matrix were applied Tocher's clustering and single linkage clustering and analysis of canonical variables. The relative importance of the descriptors was also evaluated. Multivariate analysis techniques allowed an effective study of genetic divergence and the grouping of the 21 accessions into five clusters. Cucurminoid content and dry weight were the traits that contributed most to genetic divergence and allowed selection of the best accessions for breeding programs to develop high-yield genotypes with high contents of cucurminoids.

An AFLP-based survey of genetic diversity among accessions of sea oats (Uniola paniculata, Poaceae) from the southeastern Atlantic and Gulf coast states of the United States

Uniola paniculata, commonly known as sea oats, is a C4 perennial grass capable of stabilizing sand dunes. It is most abundant along the Gulf of Mexico and southeastern Atlantic coastal regions of the United States. The species exhibits low seed set and low rates of germination and seedling emergence, and so extensive clonal reproduction is achieved through production of rhizomes, which may contribute to a decline in genetic diversity. To date, there has been no systematic assessment of genetic variability and population structure in naturally occurring stands in the USA. This study was conducted to assess the genetic relationship and diversity among nineteen U. paniculata accessions representing eight states: Texas, Louisiana, Mississippi, Alabama, Florida, South Carolina, North Carolina, and Virginia, using amplified fragment length polymorphism (AFLP). Twelve AFLP EcoRI + MseI primer combinations generated a wide range of polymorphisms (42-81%) with a mean of 59%. Overall, the sea oats plants exhibited a low range of genetic similarity. Florida accessions, FL-33 and FL-39, were most genetically diverse and the accessions from both Carolinas and Virginia (NC-1, NC-11, SC-15, and VA-53) harbored less genetic variability. Cluster analysis using the UPGMA approach separated U. paniculata plants into four major clusters which were also confirmed by principal coordinate analysis (PCO). Further examination of the different components of genetic variation by analysis of molecular variance (AMOVA) indicated the largest proportion of variability at the state level (47.8%) followed by the variation due to the differences among the genotypes within an accession (34.4%), and the differences among the accessions within a state (17.8%). The relationship between genetic diversity and geographic source of sea oats populations of the United States as revealed through this comprehensive study will be helpful to resource managers and commercial nurseries in identifying suitable plant materials for restoration of new areas without compromising the adaptation and genetic diversity.

Genotype and Environment Affect Rhizome Growth of Birdsfoot Trefoil

Rhizome production has been transferred from wild germplasm of Lotus corniculatus L. (broadleafed birdsfoot trefoil) into domesticated germplasm to produce ‘ARS‐2620’ and ‘ARS‐2424’ (a L. corniculatus × L. uliginosus hybrid). The objective of this study was to determine if field environments in the United States differing in latitude affect rhizome expression in genotypes of ARS‐2620 and ARS‐2424. Ramets of rhizomatous genotypes of ARS‐2620 and ARS‐2424, and nonrhizomatous ‘Norcen’ were planted at seven locations in late July and August 1999. At five locations in 2000 and 2001, dormant plants were hand‐dug in late autumn or winter. Traits measured were mean crown‐plus‐root mass, crown circumference, and percentage survival for all entries, and rhizome mass for the two rhizomatous entries. Significant (P ≤ 0.001) location × genotype effects were observed for all traits in 2000, but only for percentage survival in 2001. In 2001, the effect of locations was significant for all traits (P ≤ 0.001), but genotype effects were significant (P ≤ 0.001) only for crown circumference and percentage survival. The rhizomatous entries were larger in circumference and had a greater crown‐plus‐root mass than Norcen. Rhizomes appeared to be beneficial to plant survival and plant growth, but rhizomes did not assure performance or survival, as we did not identify a genotype that performed well across locations. High plant mortality and extensive tissue necrosis caused by root and crown‐rot complex reduced overall plant performance and rhizome expression and masked the interpretive value of the data from the five locations. Plants grown in Logan, UT, were notable for their large size and rhizome production relative to the other locations, and as having advantageous, but undefined, environmental conditions beneficial to the performance of rhizomatous birdsfoot trefoil.

Morphological Development of Lingonberry as Affected by In Vitro and Ex Vitro Propagation Methods and Source Propagule

The growth and development of lingonberry (Vaccinium vitis-idaea L.) plants propagated either by conventional softwood cuttings or by in vitro shoot proliferation from nodal explants and by shoot regeneration from excised leaves of micropropagated shoots, were studied in cultivars `Regal', `Splendor', and `Erntedank'. Significant differences were observed between the treatments. After 3 years of growth, the in vitro-derived plants produced more stems, leaves, and rhizomes than the conventional cuttings which rarely produced rhizomes. In vitro culture on nutrient medium apparently induces the juvenile branching characteristics that favor rhizome production. This increase in vegetative growth and rhizome yield of in vitro-derived plants over stem cuttings varied among genotypes.

EFFECT OF PLANTING DEPTH AND DENSITY, LEAF REMOVAL, CYTOKININ AND GIBBERELLIC ACID TREATMENTS ON FLOWERING AND RHIZOME PRODUCTION IN ZANTEDESCHIA AETHIOPICA

Zantedeschia (Fam. Araceae), a genus of 6 or 7 species, are all native to South Africa, They generally grow in wet, marshy land often at the edge of forests. Z. aethiopica is used in Israel for cut flower production, as well as for rhizome propagation. The crop is mainly grown in unheated greenhouses during winter and early spring. Annual production of Z. aethiopica has increased rapidly over the last few years. This paper reports results of a series of studies on the influence of planting depth and density, leaf removal and growth regulator treatments (gibberellic acid (GA) and benzyl adenine (BA)) on flowering and rhizome production. The objective was to define optimum growing procedures for the production of high yields of top quality Z. aethiopica flowers and rhizomes during the December to May winter growing season in Israel. We found that flower yield was high when rhizomes were planted at a depth of 10 cm below the soil surface. Deeper planting (20 cm) yielded highest rhizome weights, whereas planting at 10 cm, yielded the highest number of rhizomes. Changing planting density did not affect the number of flowers produced per plant, but close planting resulted in longer flower stems. Leaf removal increased flower yield. Dipping rhizomes in 350 ppm BA followed by a dip in 350 ppm GA3 increased flower yield five fold over the control. However, a dip with only BA, yielded the same number of flowers, as the combined treatment. Although many malformed or green flowers developed as a result of GA3 treatments, combination treatments with BA or BA alone reduced the extent of this problem.

Recovery of deep Posidonia oceanica meadows degraded by trawling

The recovery capacity of meadows of the Mediterranean seagrass Posidonia oceanica (L.) Delile in an area affected by illegal trawling were assessed after protection by anti-trawling reefs. The differences in vegetative growth between two impacted and two undisturbed localities were tested using growth, shoot balance, aborted branches, and leaf and rhizome production of both plagiotropic and orthotropic rhizomes. The organic matter in sediments, silt clay fraction and light intensity incident on the bottom were also measured in order to evaluate the physical conditions. Environmental and plant variables were measured in three sites placed inside each locality. The vegetative growth was positive in both impacted and control meadows but growth rates were lower in impacted than in control meadows. Average growth, production and shoot balance were greater in plagiotropic rhizomes from undisturbed localities (40.7±1.75 vs. 28.4±1.34 mm/year, 1133±0.06 vs. 708±0.04 mg DW/shoot/year, 1.36±0.08 vs. 0.96±0.06 shoots/year, respectively). Significantly greater values were also found in undisturbed localities for orthotropic rhizomes in terms of shoot balance and rhizome production (0.07±0.01 vs. 0.01±0.003 shoots/shoot/year and 155 vs. 124 mg DW/shoot/year, respectively). Of the physical parameters measured, only light intensity differed significantly between impacted and undisturbed localities. This parameter was 15.5% to 67.6% lower in impacted localities than in undisturbed localities, and this is the factor that causes the retardation of vegetative growth. The results show that recovery of P. oceanica meadows is possible after eliminating the cause of the impact. However, the very low rates of vegetative growth may prolong the time to total recuperation to almost 100 years. Therefore, effective management of P. oceanica meadows should aim to prevent meadow loss.

Carbon resource sharing and rhizome expansion of Phalaris aquatica plants in grazed pastures.

The patterns of carbon (C) resource sharing and new rhizome development in phalaris (Phalaris aquatica L. cv. Australian) were examined in grazed pastures in western Victoria. The seasonal pattern of new rhizome growth was similar under the four grazing systems tested. New rhizome production was infrequent but concentrated in winter. The phalaris plants maintained more than 1600 kg DW ha-1 of non-assimilating material beneath the soil surface (0-5 cm). Gaseous 14C was fed into plants in the field to determine if these below ground structures continued to be supported by the C assimilating tillers. The results indicated that the primary tiller does provide C to support the growth of secondary and tertiary tillers derived from its axillary buds. There was some evidence that C was exported from the fed tiller to non-assimilating plant structures. The old reproductive tiller bases (from which the assimilating tillers originate) received some C support, suggesting that this was maintained because it had deep roots attached. C export to older plant parts declined, which may lead to plant fragmentation.

Population-level effects of clam harvesting on the seagrass Zostera noltii

Seagrass declines have been reported worldwide, mostly as a consequence of anthro- pogenic disturbance. In Ria Formosa lagoon, southern Portugal, the intertidal meadows of Zostera noltii are highly disturbed by clam harvesters. The most common technique used to collect the clams consists of digging and tilling the sediment with a modified knife with a large blade. Here we present both descriptive and experimental evidence of the negative effects of clam harvest on the Z. noltii populations of Ria Formosa. A comparison between disturbed and undisturbed meadows suggests that clam harvesting activities change the species population structure by significantly reducing shoot density and total biomass, particularly during August, when the harvest effort is higher. Exper- imental harvest revealed a short-term impact on shoot density, which rapidly recovered to control levels during the following month. An experimental manipulation of rhizome fragmentation revealed that plant survival is reduced only when fragmented rhizomes are left with 1 intact internode. Shoot production and rhizome elongation and production of fragmented rhizomes having 2 to 5 internodes were not significantly affected, even though growth and production were lower when only 2 intern- odes were left. Experimental shoot damage at different positions along the rhizome had a significant effect on plant survival, rhizome elongation, and production only when the apical shoot was removed. Our results show that clam harvest can adversely affect Z. noltii meadows of Ria Formosa while revealing a low modular integration that allows the species to rapidly recover from physical damage.

Effect of plant density and depth of harvest on the production and quality of licorice (Glycyrrhiza glabra) root harvested over 3 years

Licorice (Glycyrrhiza glabra) root production was investigated in Central Otago, Canterbury, and Waikato regions of New Zealand over 4 years. Increasing plant populations at establishment had a large effect on production. Maximum root and rhizome production was achieved with plant populations above 24 000 plants/ha. Low plant densities favoured rhizome production and high densities favoured root production. Sampling roots and rhizomes to 900 mm showed that the majority of production was in the top 300 mm. Roots harvested from below 300 mm contained less glycyrrhizin than surface roots. Glycyrrhizin concentration increased each year and surpassed the minimum international standard of 4% in the first harvest in the Waikato but not until the third harvest at South Island sites. By the third harvest both Waikato and Canterbury grown licorice contained similar amounts of glycyrrhizin but with 90% of the glycyrrhizin content in roots in the 0–300 mm soil layer in the Waikato and in the 0–600 mm soil layer in Canterbury. These trials show that licorice can be grown in New Zealand with fresh root and rhizome yields of 17–28 t/ha in the second and third years of production and with a glycyrrhizin content above the minimum international standard.

Morpho-chronological variations and primary production in Posidonia sea grass from Western Australia

The occurrence of morpho-chronological variations was demonstrated in three Australian species of phanerogams, Posidonia australis, Posidonia coriacea and Posidonia sinuosa, which are found living around Rottnest Island (Western Australia). Three chronological parameters were identified: the thickness of dead sheaths, the internodal distance and the regular presence of floral stalk remains. The foliar primary production for these three species, as estimated using the lepidochronology method, is very high since values of 1374, 1811 and 678 mg dw shoot−1 y−1 were recorded, respectively. Rhizome production values range from 70·6 and 376·7 mg dw shoot−1 y−1 for Posidonia coriacea and Posidonia australis respectively. The results obtained are very encouraging and confirm that these morpho-chronological variations are particularly well developed for the genus Posidonia.

Época e densidade de plantio na produção de cúrcuma

Com o objetivo de avaliar a produtividade da cúrcuma em função da época e densidade de plantio, este experimento foi instalado no período de outubro de 1994 a julho de 1995, em campo, na Universidade Federal de Lavras, no município de Lavras-MG. Foram avaliados os fatores épocas de plantio (20/out, 20/nov, 20/dez e 20/jan) e espaçamento entre plantas na linha de plantio (0,20; 0,35 e 0,50m), sob delineamento de blocos ao acaso, em parcelas sub-divididas, com três repetições. A produção de rizomas por planta e por área foram influenciados significativamente pela interação dos fatores avaliados. Maiores produtividades por planta (673,13g) e por área (24.678,82kg ha-1) foram obtidas nos plantios de 20 de novembro e espaçamentos entre plantas, respectivamente, de 0,36 e 0,30m.