Petiole Weight Research Articles

Towards the establishment of “lagundi” (Vitex trifolia s.l.) reference germplasm from the Philippines: An agro-morphological and phytochemical evaluation of native genotypes

An identified reference germplasm is needed to facilitate the stable sourcing of medicinal plants with correct genotype(s). We aimed to evaluate phytochemical and agro-morphological properties of four pre-selected, genetically stable, and native Vitex trifolia s.l. accessions from the Philippines to provide baseline information and present promising and available genetic materials as standards. Yield and yield components of four V. trifolia s.l. accessions from the Philippine Biorepository Network (PBN) were evaluated using a randomized complete block design in one growing season. Quantification of macromolecules of the dried samples were determined through proximate analysis. Phytochemicals were qualitatively screened while antioxidant activity were evaluated for total phenolic content, DPPH radical scavenging activity, and hydrogen peroxide scavenging activity. PBN 2019–138 had the highest dry yield at 128 ± 21.16 g per plant and showed moderate to high antioxidant activity. Its high biomass throughput was attributed to its higher number of leaves per plant, heavier petiole weight, and high fiber content at 25.29%. PBN 2019–332 exhibited the highest antioxidant activity among all assays but with relatively lower fiber content (24.24%) and lower yield at 60.62 ± 17.63 g per plant. The genotypes varied significantly in 17 out of 29 evaluation parameters. Thirteen traits had moderate to high heritability values, indicating the potential for clonal selection of promising types. Using principal component analysis, we identified PBN 2019–138 as the most promising genotype across the four accessions as it had the highest leaf yield per plant and intermediate antioxidant activity. Thus, the accessions presented can be asexually propagated and used as genotypic standards for subsequent RDE activities centered on the medicinal use of V. trifolia s.l. genotypes.

Nano-iron oxide accelerates growth, yield, and quality of Glycine max seed in water deficits.

Drought is one of the most destructive abiotic stresses that impact the growth, physiology, yield, and nutritional quality of seeds of crop plants. In modern agriculture, the use of nanoparticles can be beneficial due to their large surface area and higher potentiality to enter into the plant leaf during foliar application. This study aims to evaluate the effects of foliar spray containing varying doses (0, 100, and 200 ppm) of the nano-iron (Fe3O4) on the growth, physiology, yield, and seed nutritional quality of soybean under drought (40% of field capacity, FC) and well-watered (80% of FC) conditions. Leaf water status, chlorophyll content of leaves, the height of the plant, fresh leaf weight, fresh stem weight, fresh petiole weight, total dry weight, seed yield, and protein and oil content in soybean seeds were found to be suppressed by the applied drought stress. Under both drought (40% of FC) and controlled well-watered (80% of FC) conditions, the foliar application of nano-iron substantially improved the growth, physiology, yield, and quality of soybean seeds. The nanoparticles at 200 ppm increased soybean seed yield by 40.12 and 32.60% in drought and well-watered conditions, respectively, compared to the untreated plants. Furthermore, nano-iron increased the oil content of soybean seeds by 10.14 and 7.87% under drought and well-watered conditions, respectively, compared to the untreated control. Our results indicate that the application of nano-iron improved drought tolerance, yield, and seed quality of soybean, so exogenous foliar sprays of 200 ppm Fe3O4 were more effective than the other treatments in enhancing drought tolerance and can be utilized to reduce losses caused by drought stress in soybean-growing areas.

Screening and evaluation of chilli (Capsicum annuum L.) genotypes for waterlogging tolerance at seedling stage

Waterlogging is an illustrious abiotic stress and the constrictions it enforces on plant roots have negative effects on growth and development. This study was undertaken to investigate waterlogging stress tolerant potential in chilli (Capsicum annum L.) genotypes through evaluating morphological, physiological, biochemical and anatomical parameters. Thirty-five days old seedlings of 10 chilli genotypes were exposed to waterlogging stress maintaining water height 3–5 cm over the soil surface artificially for three days. This duration (36–38 DAE) was termed as waterlogging period, and subsequent withdrawal of waterlogging condition (39–45 DAE) was regarded as a recovery phase. Based on their survival performance, two tolerant genotypes viz., SRC-517 and BARI morich-2 and two susceptible genotypes viz., AHM-206 and RI-1(6) were selected for studying stress tolerance mechanism. Under waterlogging, however, both genotypes (tolerant and susceptible) exhibited reduced root shoot length, dry weight ratio, petiole weight and leaf area, and noticeable reduction regarding these parameters was observed in susceptible genotypes. Moreover, tolerant genotypes displayed a higher recovery than susceptible genotypes after removal of waterlogging stress. Lower reduction of leaf area and photosynthetic pigments as well as higher reduction of relative water content (RWC) were noticed in susceptible genotypes. Higher accumulation of proline and total antioxidant capacity (TAC) during waterlogging condition in tolerant genotypes suggested lower oxidative damage. Although both genotypes lost total soluble sugar (TSS) relative to control at waterlogging stress, better performance was recorded in tolerant genotypes. During the period after the removal of extra water, a similar genotypic response in terms of TSS gain was seen. Undoubtedly, under flooding conditions, the development of aerenchyma cells in tolerant genotypes is a means of tolerance mechanism for long-term survival. Thus, the morpho-physiological and biochemical changes help to understand the tolerance mechanism in chilli under waterlogging stress.

Growth and yield performance of strawberry (Fragaria ananassa) under various doses of vermicompost and NPK fertilizers grown at rooftop of Charfasson area in the southern parts of Bangladesh

A pot experiment was carried out on the rooftop of a building at Charfasson town Bhola to evaluate the growth and yield performance of strawberry (Fragaria ananassa) as influenced by different doses of vermicompost and inorganic fertilizers in the winter season of 2020-2021. Each pot was filled with ten kg soil and arranged in a completely randomized design having seven treatments with three replications. Treatments were T1: Control (-VC), T2: 5 t VC/ha, T3: 10 t VC/ha, T4: 15 t VC/ha, T5: 20 t VC/ha, T6: 25 t VC/ha, and T7: 50% RDF NPK (40 - 15-25 kg/ha). Different agronomic parameters were measured at the intervals of 30, 60, 90, and 120 days after sowing of seeds. All the treatments of vermicompost showed better responses in agronomic parameters than the control treatment. Among them, T5 treatment tends to show significantly (p<0.05) higher plant height (18.5 cm), number of the leaf (54/plant), root length (15.50 cm), first flowering (at 61 days), fruit length (5.75 cm), fruit diameter (13.75 cm), number of fruits (15/plant), the average weight of fruit (14.50 g), the fresh yield of fruits (13.59 t/ha), fresh weight of root (10.41 g/plant), fresh weight of reproductive structure (3.12 g/plant), weight of the dry reproductive structure (3.12 g/plant) and benefit-cost ratio (9.37). T6 treatment showed significantly (p<0.05) higher leaf area (49.00 cm2), fresh weight of petiole (4,61 g/plant), the weight of dry root (2.20 g/plant), weight of dry leaf (5.87 g/plant), weight of dry petiole (1.42 g/plant) and weight of dry biomass (12.48 g/plant). T2, T3 and T4 treatments showed significantly (p<0.05) higher growth than T7 treatment. The overall findings revealed that the application of vermicompost (20 t/ha) in the strawberry plant might be a suitable method in rooftop gardening to achieve its better agronomic and yield parameters in the southern parts of Bangladesh.
 Dhaka Univ. J. Biol. Sci. 30(2): 283-292, 2021 (July)

Screening and Assessment of Selected Chilli (Capsicum annuum L.) Genotypes for Drought Tolerance at Seedling Stage

This study was undertaken to investigate oxidative stress tolerant mechanisms in chilli (Capsicum annuum L.) under drought genotypes through evaluating morphological, physiological, biochemical and stomatal parameters. Twenty genotypes were evaluated for their genetic potential to drought stress tolerant at seedling stage. Thirty days old seedlings were exposed to drought stress induced by stop watering for the following 10 days and rewatering for the following one week as recovery. Based on their survival performance, two tolerant genotypes viz. BD-10906 and BD-109012 and two susceptible genotypes viz. BD-10902 and RT-20 were selected for studying the oxidative stress tolerance mechanism. Drought reduced root and shoot length, dry weight, ratio, petiole weight and leaf area in both tolerant and susceptible genotypes, and a higher reduction was observed in susceptible genotypes. Lower reduction of leaf area and photosynthetic pigments were also found in tolerant genotypes. Moreover, tolerant genotypes showed higher recovery than susceptible genotypes after the removal of stress. A higher reduction of relative water content (RWC) may cause an imbalance between absorbed and transpirated water in susceptible genotypes. Higher accumulation of proline in tolerant genotypes might be helpful to for better osmotic maintenance than that in susceptible genotypes. Tolerant genotypes showed higher antioxidant activity as they showed DPPH radical scavenging percentage than the susceptible genotypes. Moreover, closer stomata in tolerant genotypes than susceptible ones helped to avoid dehydration in tolerant genotypes. Thus, the above morphological, physiological, biochemical and stomatal parameters helped to show better tolerance in chilli under drought stress.

Population ecology in a naturalsyneilesis palmata stand: II. vegetative growth and population structure

Vegetative growth and changes within populations ofSyneilesis palmata (THUNB>) MAX. Usannamul were monitored in two natural stands with different levels of incoming light. This perennial, shade-tolerant herb was measured for its plant size, petiole length, leaf breadth, and leaflet number over 11 years in a moderately shaded (MS) stand and over 7 years in a severely shaded (SS) stand. At the end of each growing season, a shoot primordium developed at the center of the root system. Correlation coefficients were mostly high between pairings of two properties - total weight, petiole length, petiole weight, leaf breadth, leaf blade weight, leaf area, specific leaf area, and leaflet number. Mean annual mortality of this species was higher in SS (22.97%) than in MS (8.85%), but great fluctuations were seen from year by year. Mortality was lowest for medium-sized plants. Regarding petiole length, differences in mean annual growth rates were conspicuous, i.e., 2.6% in MS and 8.4% in SS, while growth rates for leaf breadth were 3.1% in MS and 24.2% in SS. Changes in plant frequency within individual size classes roughly showed a normal distribution curve. However, the mode varied year by year, and such changes were more remarkable in SS than in MS. Under severe shading,S. palmata had a higher growth rate and but also greater mortality than did plants under moderate shade. Therefore, one can conclude that the population structure in SS was unstable over time.

REGRESSION MODELS TO ESTIMATE LEAF SHEET AREA AND BIOMASS OF ORGANS IN YOUNG APPLE TREES

In apple trees, leaf sheet area and shoot biomass are basic variables in growth, source-sink relationships and productivity researches. The aim of this studio was to build empirical mathematical models using multiple linear regression techniques to estimate leaf sheet area (LSA) and shoot biomass in “Agua Nueva II” young apple trees. All linear regression models obtained have high precision (R2 above 0.969). LSA (in square centimeters) was estimated with the model LSA= -3.24140(MWS) + 0.67616(MWS)2 + 1.63287(MWS)(LS/MWS), where MWS stands for maximum wide of leaf and LS for leaf length. The dry weight of leaf sheet (DWLS) was estimated with the model DWLS= 0.02699(LSA) + 0.00021917(LSA)2. The dry weight of petiole (DWP) was estimated as DWP = 0.00384(LSA) - 0.04432(LS/MWS) + 0.02291(LS/MWS). The dry weights (in g) of radical system (DWRS), of stem (DWS), of principal stem (DWPT), of large branches (DWBL), of medium branches (DWBM), and of short branches (DWBS) are a function of fresh branch volume (FV). The formulae of truncated cone was used to calculate FV (in cubic centimeters); for this, it was required proximal (basal) and distal (apical) diameters of branches, and its length. The branch dry weights were estimated with the following models: DWP = 0.66882(FV), DWPT = 0.55902(FV), ln(DWBL) = 0.77462[ln(FV)], DWBM = 0.49349(FV) and DWBS = 0.57297(FV). The model for dry weight of radical system (DWRS) is function of length and distal diameter of trunk: DWRS = 10.80747(LPT)(DDT) + (-01.37171) (DDT)2 The length and diameter variables in leaf, trunk, stem and branches were expressed in centimeters.

Morphological adaptations byGlehnia littoralis to the biomass and heights of peripheral herbaceous plants in coastal sand dunes

To clarify the effects of peripheral herbal plants onGlehnia littoralis growth in coastal sand dunes, the morphology of their aboveground portions was surveyed in five communities:Carex kobomugi, Calystegia soldanella, Ischaemum anthephoroides, Oenothera biennis, andElymus mollis. Correlation coefficients (CC) were generally significant at the 1% level between community properties [total aboveground biomass (B) and height (H) of dominant species per unit area] and those ofG. littoralis [leaf number (Nl), petiole angle (Anp), petiole length (Lp), petiole weight (Wp), Lp/Wp, Lp/weight of leaf blade (Wb), Wp/total weight (Wt), specific leaf area (SLA), stem length (Ls), and Ls/weight of stem (Ws)J The exceptions were among four pairings: B and NI, B and Wt, H and Nl, and H and Wt. Of the two community properties, biomass had the greatest association with leaf properties while H was most closely related to those of the stems. Petiole angle increased along with leaf order, from 0° to 42° for the C.kobomugi community, from 5° to 55° forCalystegia soldanella, from 49° to 74° forI. anthephoroides, from 54° to 80° forO. biennis, and from 75° to 85° forE. mollis. In all communities, the properties of Wp, SLA, and Wb increased up to the third or fourth leaf, but then decreased; the exception was for Lp/Wp, which was the reverse. Leaf order of the largest one moved from first position to third as either B or H increased in a community.

Differential effects of clonal integration on performance in the stoloniferous herb Duchesnea indica, as growing at two sites with different altitude

Clonal integration may be adaptive and enhance the genet performance of clonal plants. Degree of clonal integration may differ between different environments . Here, a container experiment was used to determine how clonal integration affected the performance of the stoloniferous herb Duchesnea indica at two sites with different altitude along the transitional zone between the Qinghai-Tibet plateau and the Sichuan basin of Southwest China. In the experiment, the stolon between partially shaded two ramets experienced severing and intact treatments.We predicted that clonal integration would increase performance of whole clonal fragments and their shaded clonal parts at both sites. In both arctic and alpine environments, clonal plants may form highly integrated plant units (group of ramets).We predicted again that the reduction due to stolon severing in performance of whole clonal fragments and their shaded clonal parts would be greater at the site with high altitude than one with low altitude. The results indicated that the benefit for the shaded clonal parts and whole clonal fragments due to clonal integration was only observed at the site with high altitude. The results suggest that the performance of Duchesnea indica tends to be more responsive to the stolon severing at the site with high altitude than one with low altitude and support the second prediction. In addition, the effects of conditions of the sites and clonal integration on local morphological traits of ramets may be adaptive, five morphological traits of ramet-level (length of petiole, mean stolon internode length, specific petiole weight, specific stolon internode weight and specific leaf area) were investigated. Altogether, the results suggest that clonal integration might help D. indica plants to successfully inhabit the high-altitude habitat of the Qinghai-Tibet plateau of Southwest China, providing new evidences for the notion that clonal integration is an adaptive trait in stressful environments.

Root Pruning Reduces Photosynthesis, Transpiration, Growth, and Fruiting of Container-grown French-American Hybrid Grapevines

`Seyval blanc' and `Vidal blanc' grapevines (Vitis sp.) grown in large containers were root-pruned at different severities and/or stages of development and the effects on growth of both cultivars and fruiting of `Seyval blanc' were determined. As the severity of root pruning increased, stomatal conductance (gs) and transpiration (E) decreased and the number of wilted leaves increased in both cultivars. In both cultivars, root pruning reduced net photosynthesis (Pn) and E for as long as 18 to 20 days, as well as total leaf area and dry weight of leaves and petioles plus tendrils. The reductions were proportional to the degree of root pruning. A similar pattern existed for cane and root tissue of `Vidal blanc'. As the severity of root pruning increased, berry and cluster weight, and titratable acidity (TA) of `Seyval blanc' decreased. There was no effect of root pruning on berries per cluster, soluble solids content (SSC), or pH of the juice. No interaction was significant for any factor between time of root pruning and fruiting measured on `Seyval blanc' vines. Root pruning at bloom reduced leaf area, number of leaves, and dry weight of petioles, trunks, and canes. Root pruning at veraison had no effect on any vegetative or fruit parameters. Fruiting `Seyval blanc' vines had less leaf area and smaller petiole and cane dry weights than did nonfruiting vines.

The role of petioles in light acquisition by Hydrocotyle vulgaris L. in a vertical light gradient.

In natural herbaceous vegetation plants are exposed to a vertical light gradient. In experiments, however, morphogenetic responses of stoloniferous plants to shade have nearly always been tested under homogeneous shade conditions. In this study we simulated a vertical light gradient and found that the response of Hydrocotyle vulgaris in this gradient differed considerably from the responses to homogenous shade. Petioles grew longer while at the same time the specific weight of petioles increased. The elongated petioles raised leaf-blades into better-lit places resulting in higher biomass. Though leaves in the light gradient started their growth under low-light conditions, the size of the leaf-blade was the same as in high light. Internodes were longer than in homogeneous shade conditions but specific weight decreased, probably due to increased allocation to the fast-growing petioles.

Ontogenic change in leaf shape and crown form of a tropical tree,Scaphium macropodum (Sterculiaceae) in Borneo

Crown architecture was analyzed forScaphium macropodum (Sterculiaceae), a common shade-tolerant emergent tree of a tropical rain forest in West Kalimantan, Indonesia. Saplings and poles shorter than 12 m in height had no branches, and gathered their leaves at the ends of the stem. The leaves changed from entire to palmately-parted with increasing tree size. The parted leaves increased the light penetration through the clustered foliage. The size of leaves including the blade and petiole ranged from 22 cm to 147 cm. Because the weight of petiole per blade increased with leaf size, the leaf could not be enlarged infinitely. Taller trees with lateral branches bore small (about 40 cm in length) entire leaves. The light intensity in the forest increased from the ground to about 12 m tall and was nearly constant from 12 m to 18 m. Crown architecture ofS. macropodum adapted to this light environment. The monoaxial trees lower than 12 m could thus increase the amount of light with vertical elongation, and the branched trees higher than 12 m could increase it by means of lateral extension of crown area.

The Influence of Elevated CO 2 and Simulated Seasonal Changes in Temperature on Tissue Turnover in Pasture Turves Dominated by Perennial Ryegrass (Lolium perenne) and White Clover (Trifolium repens)

1. Tissue turnover, leaf morphology and population dynamics of perennial ryegrass and white clover were studied in pasture turves grown at ambient (350 μmol mol −1 ) or double ambient (700 μmol mol −1 ) CO 2 concentrations for 217 days in controlled environment rooms. The turves were subjected sequentially to three day/night temperature regimes; 10/4°C, 16/10°C and 22/16°C and harvested at 3-week intervals. The photoperiod was 12 hours for all of the temperature treatments with a mean photon flux density of 480 μE m −2 s −1 . 2. Ryegrass leaf extension and leaf death rates did not differ between CO 2 treatments and there was no effect of CO 2 on rates of leaf appearance in white clover. Weight per unit length of ryegrass laminae was unaffected by elevated CO 2 but lamina weight per unit area, lamina area and petiole weight per unit length in white clover showed a small positive response, especially at the two higher temperatures. Rates of growth and senescence per ryegrass tiller were therefore similar between CO 2 treatments, but rates of growth per white clover growing point were increased by 4, 23 and 13% at 10/4°C, 16/10°C and 22/16°C, respectively, at elevated CO 2 . Responses to CO 2 could not be attributed to any consistent change in morphological characteristics in either species and exposure to elevated concentrations of CO 2 did not appear to change the relationship between growth and senescence per meristem. 3. Total grass tiller populations were similar at both CO 2 concentrations, but ryegrass tiller densities more than halved in both CO 2 treatments as the temperature was increased. The fall was most severe at 700 μmol mol −1 and at the end of the experiment ryegrass tiller densities in this treatment were only 47% of those found at 350 μmol mol −1 . There was no consistent effect of CO 2 concentration on clover growing point numbers and they increased from 800 m −2 to over 3000 m −2 in both treatments with maximum densities occurring at 22/16°C. 4. The results imply that, in plant communities dominated by ryegrass and white clover, exposure to elevated CO 2 concentrations will alter the species composition in favour of white clover. Responses in above-ground dry matter yield to elevated CO 2 will be a balance between the positive response shown by white clover and the negative response of perennial ryegrass. Temperature will have a major influence on the magnitude of this response since both the response of white clover to CO 2 and the ratio of white clover growing points to ryegrass tillers are temperature-dependent

An Environmentally Controlled Experiment to Monitor the Effect of Aphanomyces Root Rot and Rhizomania on Sugar Beet

An experiment was initiated to determine how sugar beets are affected by Aphanomyces cochlioides and beet necrotic yellow vein virus (BNYVV), the causal agents of Aphanomyces root rot and rhizomania, respectively. The experiment was conducted in a controlled temperature box maintained at 27±2 C. Treatments consisted of soil infested with Aphanomyces, BNYVV, both pathogens combined, and an untreated control. At 8 and 12 wk after planting, leaf and petiole weights and leaf areas were taken. At harvest, tops were removed, and the soil cores were divided into three 15-cm segments and washed. After 8 wk, leaf weights and leaf areas for the control treatment were significantly higher than those for the pathogen treatments [...]

Sodium chloride and soil texture interactions in irrigated field grown sultana grapevines. II. Plant mineral content, growth and physiology

Effects of salinity on the mineral composition, growth and physiology of field-grown sultana grapevines were studied by adding NaCl solution to River Murray water. Five salt treatments, ranging between 0.37 and 3.47 dS m-l, were applied for six seasons. Petiole levels of Cl and Na were better predictors of yield than were lamina levels. There was no evidence of safe threshold salinity levels, so grapevine growers should aim to keep tissue salinity levels as low as possible, certainly below 1.5% and 0.5% for petiole Cl and Na respectively. Yield was affected not only by the salinity of the tissue in the current season, but also by tissue salinity in the preceding seasons. A model was developed which included previous tissue salinity measurements. Salt treatment reduced all growth parameters measured-pruning weight, shoot length, cane number and leaf and petiole weight. Decreases in stomatal conductance and photosynthesis were measured in the field in leaves of salinised vines, but leaf water potential was not affected. These decreases in photosynthetic rate are the probable cause of the severe yield and growth reductions in salinised vines.

THE ELASTIC MODULI AND MECHANICS OF POPULUS TREMULOIDES (SALICACEAE) PETIOLES IN BENDING AND TORSION

Changes attending leaf development in the mechanical behavior and elastic moduli of the petioles of Populus tremuloides Michx. were examined in terms of total leaf weight (Wt), lamina and petiole weight (Wl and Wp), petiolar length (L), and lamina surface area (A). A primary concern was the extent to which two elastic moduli (Young's modulus E and the shear modulus G) of petioles changed over time and were correlated with one another. E and G were measured by means of multiple resonance frequency spectra, and together with the dimensions of cross sections through petioles, these two elastic moduli were used to estimate the stiffness of petioles in simple bending and torsion. Petiolar bending was predicted by means of a model incorporating expressions for both the bending stiffness (El) and torsional rigidity (GJ), where I is the second moment of area and J is the torsional constant. The predictions from these models were compared to observed petiolar bendings due to Wl. Additionally, the frequency of the oscillatory motion of leaves (placed in a wind tunnel with a 1 m sec‐1 ambient wind speed, directed normal to the blade of the leaf) was determined. Results indicate that L, A, Wl, Wp, and Wt were positively correlated with the age of leaves (crudely estimated as a function of leaf plastochron index, LPI); these morphometric parameters were also correlated with the magnitudes of E and G. Also, G was positively and linearly correlated with E, and was, on the average, an order of magnitude less than E. EI and GJ were positively correlated with LPI. The relationships among E, G, EI, C and Wl, Wp, Wt are discussed in terms of leaf allometries.

Evaluation of Propagating Stock and Practices for Annual Rhubarb Production

Yield and quality of seedand vegetatively propagated rhubarb (Rheum rhabarbarum L.) for annual production were evaluated for four seasons. Selection of `Victoria' seedlings based on petiole color was not effective in increasing the proportion of red mature petioles. Yields from seed-propagated annual rhubarb were always higher than yields from single-bud crown divisions and from crown divisions in 1 of 2 years. Petiole color of vegetatively propagated rhubarb was always superior to that of seed-propagated rhubarb. GA applications increased early yield from single-bud divisions, but reduced petiole weight of early and total harvest of `McDonald' rhubarb. Chemical name used: gibberellic acid (GA).

EVALUATION OF PROPAGATING STOCK AND PRACTICES FOR ANNUAL RHUBARB PRODUCTION

Yield and quality of seed- and vegetatively-propagated rhubarb [Rheum rhabarbarum L.) for annual production were evaluated for 4 seasons. Field planting of transplants or crown divisions in late October or early November resulted in harvests beginning in early to late January and continuing until late April. Selection of `Victoria' seedlings based on petiole color was not effective in increasing the proportion of red mature petioles. Yields from seed-propagated annual `Victoria' rhubarb were always higher than yields from `McDonald' single-bud crown divisions and higher than yields from `McDonald' crown-divisions in one of two years. The four-year average yield for `Victoria' seed-propagated rhubarb was 20.4 Mg·ha-1 whereas `McDonald' crown-division-propagated rhubarb had a two-year average yield of 15.8 Mg·ha-1. On the other hand, petiole color of vegetatively-propagated rhubarb was always superior to that of seed-propagated rhubarb. GA applications increased early yield from `McDonald' single-bud divisions, but reduced early and total harvest petiole weight.

Genotypic and non-genetic variation of oxalate and malate content in rhubarb (Rheumspp. L.)

SummaryRheum spp. genotypes represented by full-grown plants maintained their ranking for total oxalate, water-soluble oxalate and malate concentration over a range of environments. The correlation between oxalate content in early seedling v. more adult stages was low, but a negative correlation between early petiole weight and oxalate content in full-grown plants may have a predictive value in breeding programmes. The oxalate concentration of each petiole increased as it aged. As the individual plant grew larger, the petioles accumulated less oxalate but more malate. The negative correlation between the contents of oxalate and malate may be functional, or may reflect biosynthetic relationships.

Long-term effects of an increased CO2 concentration on terrestrial plants in model ecosystems. Morphology and reproduction ofTrifolium repens L.and Lolium perenne L.

Mixtures (ratio 1∶1, 45 seeds·dm−2) of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) were enclosed in environmentally controlled acrylic mini-glasshouses and supplied with additional CO2 from September 1981 until September 1982 (547–600 ppm, control: ∼340 ppm CO2). At growth optimum the single leaf area of white clover was 30% greater and the specific leaf weight 19% higher with additional CO2; with the perennial ryegrass it was 18% resp. 29%. The length growth of the white clover petioles was enhanced by the additional CO2: in the beginning 67% longer leafstalks, at growth optimum no effect and at the end of the experiment 100%. At growth optimum the specific petiole weight was approximately 52% higher. When the growing was terminated the blades of perennial ryegrass were 19% longer at high CO2. The average volume of the flowerheads was about 53% greater and the adult ears 13% longer. The number of flowers per flower head and the number of earlets per ear did not increase significantly. On an average the white clover seeds were 28% heavier and the caryopses were 4% lighter.