Effect of cultural methods on leaf spot (<Emphasis Type="Italic">Mycosphaerella fragariae</Emphasis>) and gray mold (<Emphasis Type="Italic">Botrytis cinerea</Emphasis>) damage in strawberries

Damage of leaf spot, caused by Mycosphaerella fragariae and gray mold also called Botrytis fruit rot, caused by Botrytis cinerea, average fruit weight and yield were evaluated with regard to cultural methods over 2years. Leaf spot damage decreased significantly by around 90% due to leaf sanitation (removal of dead and leaf spot infected leaves in early spring) and by 50% due to plantation in a one-row-system instead of a two-row-system. When all leaves including the healthy green ones were removed in early spring, average fruit weight decreased significantly by 10%. Fruit sanitation – the third treatment – did not influence any of the measured parameters. Neither leaf sanitation nor fruit sanitation (removal of damaged fruits during harvest) reduced B. cinerea damage significant. Only the combination of a one-row-system, leaf sanitation and fruit sanitation almost halved (not significantly) B. cinerea damage in the first crop year compared to a two-row-system without leaf and fruit sanitation. B. cinerea damage correlated significantly and positively with the biomass of plants by R²= 0.47. According to this study and the cited literature it is suggested for humid Central European conditions to apply a one-row-system combined with leaf sanitation in early spring and fruit sanitation during harvest if fruit density is high, to reduce the risk of damages in larger dimension caused by M. fragariae and B. cinerea.     

Grapevine leaf gas exchange, plant growth, yield, fruit quality and carbohydrate reserves influenced by the grape leafhopper,Empoasca vitis

The impact of the grape leafhopper,Empoasca vitis, on leaf gas exchange, plant growth, yield, fruit quality and carbohydrate reserves of the grapevines,Vitis vinifera L., was studied. Gas exchange was measured on the discolored (red) and the green parts of infested main leaves and on leaves from uninfested vines. Photosynthesis and mesophyll conductance were severely reduced on main leaves showing leafhopper feeding symptoms. The stomatal conductance of the red leaf section of infested main leaves was lower than on undamaged control leaves. Additionally, the red leaf section of infested main leaves showed lower transpiration rates when compared to the green parts of the same leaves and to undamaged control leaves. Gas exchange processes of lateral leaves were not affected by leafhopper feeding. Leafhopperload on main leaves was correlated to visual damage symptoms. At 71.8 leafhopper-days per leaf up to 40% of the main leaf area of the infested plants was discolored from the borders towards the center. Lateral leaves showed no feeding symptoms. Shoot diameter, pruning weight and carbohydrate reserves in the wood were not affected by leafhoppers. Lateral leaf area growth was significantly stimulated on plants infested by leafhoppers. No decrease in yield and fruit quality with leafhopper-loads up to 71.8 leafhopper-days per leaf were observed.     

Quantification of N2-fixation and survival of inoculated diazotrophs associated with roots of Kallar grass

White clover plants were grown for 97 days under two temperature regimes (20/15°C and 8/5°C day/night temperatures) and were supplied with either small amounts (a total of 80 mg N pot^–1) of ammonium (NH ₄ ⁺ ) or nitrate (NO ₃ ^– ) nitrogen, or received no mineral N and relied on N₂ fixation. Greatest growth and total leaf area of clover plants occurred in N₂ fixing and NO ₃ ^– -fed plants grown at 20/15°C and poorest growth occurred in NH ₄ ⁺ -fed plants grown at 8/5°C. Nodule mass per plant was greater at 8/5°C due to increased nodule numbers rather than increased dry weight per nodule. This compensated to some extent for the reduced N₂-fixing activity per unit dry weight of nodule tissue found at the low growth temperature up to 116 d after sowing, but thereafter both activity per nodule dry weight and activity per plant were greater at the low temperature. Highest nitrate reductase activity (NRA) per g fresh weight and total activity per leaf, petiole or root occurred in NO ₃ ^– -fed plants at 8/5°C. Low growth temperature resulted in a greater partitioning of total plant NRA to the roots of NO ₃ ^– -fed plants. The results are considered in relation to the use of N fertiliser in the spring under field conditions.     

CO2 alters water use,carbon gain,and yield for the dominant species in a natural grassland

Global atmospheric CO₂ is increasing at a rate of 1.5–2 ppm per year and is predicted to double by the end of the next century. Understanding how terrestrial ecosystems will respond in this changing environment is an important goal of current research. Here we present results from a field study of elevated CO₂ in a California annual grassland. Elevated CO₂ led to lower leaf-level stomatal conductance and transpiration (approximately 50%) and higher mid-day leaf water potentials (30–35%) in the most abundant species of the grassland, Avena barbata Brot. Higher CO₂ concentrations also resulted in greater midday photosynthetic rates (70% on average). The effects of CO₂ on stomatal conductance and leaf water potential decreased towards the end of the growing season, when Avena began to show signs of senescence. Water-use efficiency was approximately doubled in elevated CO₂, as estimated by instantaneous gas-exchange measurements and seasonal carbon isotope discrimination. Increases in CO₂ and photosynthesis resulted in more seeds per plant (30%) and taller and heavier plants (27% and 41%, respectively). Elevated CO₂ also reduced seed N concentrations (9%).     

Increases in cell elongation,plastid compartment size and phytoene synthase activity underlie the phenotype of the<Emphasis Type="Italic"> high pigment-1</Emphasis> mutant of tomato

A characteristic trait of the high pigment-1 ( hp-1) mutant phenotype of tomato ( Lycopersicon esculentum Mill.) is increased pigmentation resulting in darker green leaves and a deeper red fruit. In order to determine the basis for changes in pigmentation in this mutant, cellular and plastid development was analysed during leaf and fruit development, as well as the expression of carotenogenic genes and phytoene synthase enzyme activity. The hp-1 mutation dramatically increases the periclinal elongation of leaf palisade mesophyll cells, which results in increased leaf thickness. In addition, in both palisade and spongy mesophyll cells, the total plan area of chloroplasts per cell is increased compared to the wild type. These two perturbations in leaf development are the primary cause of the darker green hp-1 leaf. In the hp-1 tomato fruit, the total chromoplast area per cell in the pericarp cells of the ripe fruit is also increased. In addition, although expression of phytoene synthase and desaturase is not changed in hp-1 compared to the wild type, the activity of phytoene synthase in ripe fruit is 1.9-fold higher, indicating translational or post-translational control of carotenoid gene expression. The increased plastid compartment size in leaf and fruit cells of hp-1 is novel and provides evidence that the normally tightly controlled relationship between cell expansion and the replication and expansion of plastids can be perturbed and thus could be targeted by genetic manipulation.     

Sex-specific physiology and source-sink relations in the dioecious plant Silene latifolia

Differences in reproductive demands between the sexes of dioecious plants could cause divergence in physiology between the sexes. We found that the reproductive effort of female Silene latifolia plants increased to more than twice that of male plants or female plants that were prevented from setting fruit by lack of pollination after 4 weeks of flowering. Whole-plant source/sink ratios of pollinated females were significantly lower than those of males or unpollinated females because of investment in fruit. We hypothesized that these differences in source/sink ratio between the sexes and within females, depending on pollination, would lead to differences in leaf photosynthetic rates. Within females, we found that photosynthetic capacity was consistent with measurement of whole-plant source/sink ratio. Females that were setting fruit had 30% higher light-saturated photosynthetic rates by 28 days after flowering than females that were not setting fruit. Males, however, had consistently higher photosynthetic rates than females from 10 days after flowering onwards. Males also had approximately twice the dark respiration rates of fruiting females. We found that female reproductive structures are longer-lived and contribute more carbon to their own support than male reproductive structures. Despite the higher rates of leaf dark respiration and lower calyx photosynthetic rates, males fix more carbon than do females. We conclude that females have a sink-regulated mechanism of photosynthesis that allows them to respond to variations in fruit set. This mechanism is not, however, sufficient to explain why male S. latifolia plants have higher rates of photosynthesis, higher source/sink ratios, and lower reproductive allocation, but fail to grow larger than female plants.     

Short-term damage-induced increases in tobacco alkaloids protect plants

Summary Leaf damage significantly increases the alkaloid content in undamaged leaves on damaged field-grown wild tobacco plants. Although field-grown pot-bound plants fail to exhibit the same damage-induced increase in alkaloid content, the ability to respond to leaf damage is restored 6 days after removing plants from their pots. Freshly hatched Manduca sexta larvae reared individually in the laboratory on the high-alkaloid foliage of damaged plants released from their pots gain less weight and eat less (57.2% and 45.7% of controls, respectively) than larvae fed low-alkaloid foliage from undamaged released plants. Moreover, larvae grow equally well on the foliage of damaged and undamaged pot-bound plants. The higher chlorophyll contents characteristic of damaged released plants did not negate the effects of the increased alkaloid contents on larval growth. Undamaged leaves from undamaged field-grown plants stem-fed nicotine solutions had elevated leaf nicotine and nornicotine contents. Larvae reared on these artificially induced leaves gain only 38.5% of the weight gained by larvae reared on low-alkaloid foliage. These results demonstrate that damage-induced increases in leaf alkaloids protect induced foliage from attack and are sufficient to explain the decreased growth of caterpillars on the foliage of damaged plants.     

The influence of nitrogen concentration and ammonium/nitrate ratio on N-uptake,mineral composition and yield of citrus

In short-term water culture experiments with different ¹⁵N labeled ammonium or nitrate concentrations, citrus seedlings absorbed NH₄ ⁺ at a higher rate than NO₃ ^–. Maximum NO₃ ^– uptake by the whole plant occurred at 120 mg L^–1 NO₃ ^–-N, whereas NH₄ ⁺ absorption was saturated at 240 mg L^–1 NH₄ ⁺-N. ¹⁵NH₄ ⁺ accumulated in roots and to a lesser degree in both leaves and stems. However, ¹⁵NO₃ ^– was mostly partitioned between leaves and roots.Adding increasing amounts of unlabeled NH₄ ⁺ (15–60 mg L^–1 N) to nutrient solutions containing 120 mg L^–1 N as ¹⁵N labeled nitrate reduced ¹⁵NO₃ ^– uptake. Maximum inhibition of ¹⁵NO₃ ^– uptake was about 55% at 2.14 mM NH₄ ⁺ (30 mg L^–1 NH₄ ⁺-N) and it did not increase any further at higher NH₄ ⁺ proportions.In a long-term experiment, the effects of concentration and source of added N (NO₃ ^– or NH₄ ⁺) on nutrient concentrations in leaves from plants grown in sand were evaluated. Leaf concentration of N, P, Mg, Fe and Cu were increased by NH₄ ⁺ versus NO₃ ^– nutrition, whereas the reverse was true for Ca, K, Zn and Mn.The effects of different NO₃ ^–-N:NH₄ ⁺-N ratios (100:0, 75:25, 50:50, 25:75 and 0:100) at 120 mg L^–1 total N on leaf nutrient concentrations, fruit yield and fruit characteristics were investigated in another long-term experiment with plants grown in sand cultures. Nitrogen concentrations in leaves were highest when plants were provided with either NO₃ ^– or NH₄ ⁺ as a sole source of N. Lowest N concentration in leaves was found with a 75:25 NO₃ ^–-N/NH₄ ⁺-N ratio. With increasing proportions of NH₄ ⁺ in the N supply, leaf nutrients such as P, Mg, Fe and Cu increased, whereas Ca, K, Mn and Zn decreased. Yield in number of fruits per tree was increased significantly by supplying all N as NH₄ ⁺, although fruit weight was reduced. The number of fruits per tree was lowest with the 75:25 NO₃ ^–-N:NH₄ ⁺-N ratio, but in this treatment fruits reached their highest weight. Rind thickness, juice acidity, and colour index of fruits decreased with increasing NH₄ ⁺ in the N supply, whereas the % pulp and maturity index increased. Percent of juice in fruits and total soluble solids were only slightly affected by NO₃ ^–:NH₄ ⁺ ratio.     

Effect of seaweed concentrate on the establishment and yield of greenhouse tomato plants

Seaweed concentrate prepared fromEcklonia maxima (Osbeck) Papenfuss, when applied as a soil drench, significantly improved the growth of tomato seedlings. Application as a foliar spray had no effect on young plants. In a second experiment SWC-treated plants exhibited early fruit ripening and a total fruit fresh weight increase of 17%. The number of harvested fruit were improved by about 10%. In this instance foliar applied SWC was more beneficial than SWC applied to the soil. The significance of these findings is discussed.author for correspondence     

Effect of soil cadmium application and pH on growth and cadmium accumulation in roots, leaves and fruit of strawberry plants (Fragaria × ananassa Duch.)

Three strawberry (Fragaria × ananassa Duch.) cultivars Rainier, Totem and Selva were grown under greenhouse conditions in a Parkhill sandy loam soil with a background DTPA-extractable Cd concentration of 0.18 mg kg^-1 and a pH of 5.1. Experimental treatments included combinations of 4 Cd applications (0, 15, 30 and 60 mg Cd kg^-1 soil) applied as CdSO₄ and 2 soil pH values 5.1 and 6.8. Both the application of Cd and pH of the soil significantly affected plant growth, yield and Cd accumulation in plant tissue anf fruit. Although roots accumulated the highest concentrations of Cd of all plant parts investigated, increased soil Cd application reduced leaf weight more than root weight. In general, yield of strawberries was decreased by an increase in amount of soil-applied Cd, however the yield response varied among cultivars. At 60 mg Cd kg^-1 soil, yield of Rainier cultivar was reduced to 17.6% of control plants. Over 90% of total Cd taken up by plants grown in Cd-treated soil accumulated in roots, regardless of the Cd level in the soil. Root Cd concentrations ranged from 2.6 mg kg^-1 (control plants) to 505.7 mg kg^-1 (Totem plants grown in soil at highest Cd and a soil pH 5.1) and were directly related to soil Cd concentrations. Cd translocation from roots to leaves and fruit was very limited, resulting in a maximum Cd concentration in root leaf tissue of 10.2 mg kg^-1. Accumulation of Cd in fruit was found to correlate well with leaf Cd, although even at the highest amount of applied Cd, fruit Cd concentration did not exceed 700 g kg^-1 of fresh weight.Contribution no. 951     

Effects of temperature and CO2 enrichment on kinetic properties of NADP+-malate dehydrogenase in two ecotypes of Barnyard grass (Echinochloa crus-galli (L.) Beauv.) from contrasting climates

Summary The apparent energy of activation (E _a), Michaelis-Menten constant (K _mfor oxaloacetate), V _max/K _mratios and specific activities of NADP⁺-malate dehydrogenase (NADP⁺-MDH; EC 1.1.1.82) were analyzed in plants of Barnyard grass from Québec (QUE) and Mississippi (MISS) acclimated to two thermoperiods 28/22°C, 21/15°C, and grown under two CO₂ concentrations, 350 l l^-1 and 675 l l^-1. E _avalues of NADP⁺-MDH extracted from QUE plants were significantly lower than those of MISS plants. K _mvalues and V _max/K _mratios of the enzyme from both ecotypes were similar over the range of 10–30°C but reduced V _max/K _mratios were found for the enzyme of QUE plants at 30 and 40°C assays. MISS plants had higher enzyme activities when measured on a chlorophyll basis but this trend was reversed when activities were expressed per fresh weight leaf or per leaf surface area. Activities were significantly higher in plants of both populations acclimated to 22/28°C. CO₂ enrichment did not modify appreciably the catalytic properties of NADP⁺-MDH and did not have a compensatory effect upon catalysis or enzyme activity under cool acclimatory conditions. NADP⁺-MDH activities were always in excess of the amount required to support observed rates of CO₂ assimilation and these two parameters were significantly correlated. The enhanced photosynthetic performance of QUE plants under cold temperature conditions, as compared to that of MISS plants, cannot be attributed to kinetic differences of NADP⁺-malate dehydrogenase among these ecotypes.     

Response ofZea mays andLycopersicon esculentum to the ethylene precursors,L-methionine and L-ethionine applied to soil

Glasshouse experiments were conducted to evaluate the influence of L-methionine (L-MET) and L-ethionine (L-ETH) added to soil on the growth of corn (Zea mays L.) and tomato (Lycopersicon esculentum), respectively. The application of L-MET and L-ETH stimulated C₂H₄ production in soil by 299- and 313-fold, respectively, over an unamended control. An L-MET treatment of 1.85 mg kg⁻¹ soil was the most effective in increasing shoot height, shoot fresh weight, internodal distance, and stem diameter in two corn cultivars, Kandy Korn and Miracle, while shoot and root dry weights, leaf width, uppermost leaf collar base distance and resistance to stem breaking were increased in the case of Kandy Korn only. A significant epinastic response was observed in the second and third leaves of tomato plants when soil was treated with L-ETH. An L-ETH treatment of 0.2 mg kg⁻¹ soil resulted in the maximum fresh fruit yield, while 0.02 and 2.0 mg kg⁻¹ gave the most fruit and greater average weight of fresh fruit, respectively. Concentrations ranging from 0.002 to 2.0 mg L-ETH kg⁻¹ soil initiated early fruit formation. Early fruit ripening was observed with an application rate of 20 mg L-ETH kg⁻¹ soil. The mechanism of action of these chemicals could either be attributed to i) substrate-dependent C₂H₄ production in soil by the indigenous microflora, ii) uptake directly by plant roots followed by metabolism within the tissues, and/or iii) a change in the balance of rhizosphere microflora affecting plant growth.     

Effect of irradiance during growth of Glycine max on photosynthetic capacity and percent activation of ribulose 1,5-bisphosphate carboxylase

The initial (in vivo) and total (activity present after preincubation with CO₂ and Mg²⁺) activities of ribulose bisphosphate carboxylase were both assayed in extracts of leaves of soybean (Glycine max) plants which had been grown under 4 different irradiance levels. The total carboxylase activity per unit leaf area decreased with decreased irradiance during growth but was not different on a dry weight basis. The initial activity as a percentage of the total activity was unchanged (approximately 95%) except in leaves of plants grown at the lowest irradiance (74%). When the plants grown at the lowest irradiance were exposed to high irradiance, the initial activity was increased to 93% of the total. Light saturated rates of photosynthesis per unit leaf area were lower and saturated at lower irradiance for plants grown at lower irradiances. Initial carboxylase activity was correlated closely (r²=0.84) with leaf photosynthesis rate on a dry weight basis.     

Polygalacturonase expression during leaf abscission of normal and transgenic tomato plants

Polygalacturonase (PG, EC 3.2.1.15), an enzyme commonly found in ripening fruit, has also been shown to be associated with abscission. A zone-specific rise in PG activity accompanies the abscission of both leaves and flowers of tomato (Lycopersicon esculentum Mill.) plants. Studies of transgenic plants expressing an antisense RNA for fruit PG indicate that although the enzyme activity in transgenic fruit is < 1 % of that in untransformed fruit, the PG activity in the leaf abscission zone increases during separation to a similar value to that in untransformed plants. The timing and rate of leaf abscission in transgenic plants are unaffected by the introduction of the antisense gene. A polyclonal antibody raised against tomato fruit PG does not recognise the leaf abscission protein. Furthermore a complementary DNA (cDNA) clone (pTOM6), which has been demonstrated to code for fruit PG, does not hybridise to mRNA isolated from the abscission-zone region of tomato leaves. These results indicate that the PG protein in abscission zones of tomato is different from that in the fruit, and that the gene coding for this protein may also be different.Abbreviation PG polygalacturonase The authors of this paper are grateful to David Jackson of the John Innes Institute, Norwich, UK for his assistance with the in-situ hybridisation work. This research was supported by an Agricultural and Food Research Council Post-Doctoral award to J.E.T., and by a grant to D.G. from the Science and Engineering Research Council Biotechnology Directorate in association with ICI seeds. The work was carried out under Ministry of Agriculture, Food and Fisheries licences.     

Effects of vapour pressure deficit on growth of temperate and tropical evergreen rainforest trees of Australia

Little is known about the effect of vapour pressure deficit (VPD) on the growth of trees. Rainforest trees of eastern Australia provide an opportunity to investigate responses to VPD in species that occur in high precipitation areas but have contrasting dry seasons—summer in the temperate south and winter in the tropical north. Growth responses to VPD were measured in eight species of Australian rainforest trees from different latitudes to investigate possible differences in their response to atmospheric drought. Previous work on these species found that the tropical species have large reductions in gas exchange with increasing VPD whereas the temperate species were mainly unresponsive to increasing VPD. Plants were grown in glasshouses for a year under either low VPD or ambient conditions of a temperate climate. All species had non-significant increases in growth rates (1–9%) of plants grown under low VPD compared with plants grown under ambient VPD. In addition, growing the species under low VPD had no effect on allocation of biomass (leaf area ratio, leaf weight ratio and root/shoot ratio). Therefore, the high sensitivity of gas exchange to increasing VPD found in the tropical rainforest trees did not have a significant, long-term effect on growth under high VPD.     

巨尾桉叶片挥发物对三种植物种子萌发及幼苗生长的化感效应

为探讨人工巨尾桉林叶片挥发物对周边农作物的化感作用,采用不同质量新鲜巨尾桉叶片及由新鲜叶片提取的桉叶油对玉米、辣椒、西红柿等三种植物种子进行处理,观测其种子萌发和幼苗生长状况。结果表明:(1)在三种被测植物中,桉树叶片挥发物对玉米种子萌发影响最小,对辣椒影响最大;(2)当叶片用量小于200g时,桉树叶片挥发物对三种植物种子萌发影响不明显,当叶片用量达400g时,能完全抑制辣椒、西红柿种子萌发,并能极显著降低玉米种子萌发(P0.01);(3)玉米幼苗芽生长随叶片用量的增加呈现先促进后抑制现象,对芽高、鲜重、干重的促进和抑制均达到显著(P0.05)或极显著水平(P0.01);(4)当叶片用量小于或等于100g时,桉树叶片挥发物对辣椒、西红柿幼苗生长影响不明显,当用量达到200g时则能极显著抑制辣椒、西红柿幼苗生长;(5)桉叶油对三种测试植物的抑制效果与叶片自然挥发物相似,且效果更显著。     

Involvement of endogenous gibberellins in the regulation of increased tomato shoot growth in solarized soil

Environmental factors often affect plant growth bymodifying the levels of endogenous gibberellins (GAs).In this study, the involvement of GAs in theregulation of enhanced shoot growth in tomato (Lycopersicon esculentum Mill.) plants grown in soiltreated by solarization (a soil disinfestation method)was investigated. Seedlings at the cotyledonary stagewere transplanted into either solarized or untreatedcontrol soil. Plants in both soils grew free of anydisease symptoms. As soon as four days after planting,seedlings in solarized soil had a higher dry weightcompared to the control. Throughout most of theexperimental period of 18 days, leaf weight ratio washigher in the solarized vs. the control soil. Treatingshoot tips of control plants with 0.1 mg^.L^-1GA₃ resulted in enhanced leaf and stem growth,thus reaching values similar to those of plants grownin solarized soil. The opposite effect was obtained bytreating plants grown in solarized soil with1 mg^.L^-1 uniconazole, a GA biosynthesisinhibitor. Quantitative GC-MS analyses revealed thatGA₁ content in one and two-weeks old transplantsgrown in various solarized soils was up to 1.8 fold,and that GA₃ content in two-weeks old plants wasup to five fold the values in the control. Theseincreases were linearly correlated with the increasein leaf dry weight. It was concluded that theincreased quantities of GA₁, and eventuallyGA₃, play a role in the increased growth oftomato shoots in solarized soil as early as seven daysafter transplanting.deceased     

Growth under UV-B radiation increases tolerance to high-light stress in pea and bean plants

Pea (Pisum sativum L.) and bean (Phaseolus vulgaris L.) plants were exposed to enhanced levels of UV-B radiation in a growth chamber. Leaf discs of UV-B treated and control plants were exposed to high-light (HL) stress (PAR: 1200 mol m^–2 s^–1) to study whether pre-treatment with UV-B affected the photoprotective mechanisms of the plants against photoinhibition. At regular time intervals leaf discs were taken to perform chlorophyll a fluorescence and oxygen evolution measurements to assess damage to the photosystems. Also, after 1 h of HL treatment the concentration of xanthophyll cycle pigments was determined. A significantly slower decline of maximum quantum efficiency of PSII (F _v/F _m), together with a slower decline of oxygen evolution during HL stress was observed in leaf discs of UV-B treated plants compared to controls in both plant species. This indicated an increased tolerance to HL stress in UV-B treated plants. The total pool of xanthophyll cycle pigments was increased in UV-B treated pea plants compared to controls, but in bean no significant differences were found between treatments. However, in bean plants thiol concentrations were significantly enhanced by UV-B treatment, and UV-absorbing compounds increased in both species, indicating a higher antioxidant capacity. An increased leaf thickness, together with increases in antioxidant capacity could have contributed to the higher protection against photoinhibition in UV-B treated plants.     

Rootless Aquatic Plant Aldrovanda Vesiculosa: Physiological Polarity, Mineral Nutrition, and Importance of Carnivory

Various ecophysiological investigations are presented in Aldrovanda vesiculosa, a rootless aquatic carnivorous plant. A distinct polarity of N, P, and Ca tissue content per dry mass (DM) unit was found along Aldrovanda shoots. Due to effective re-utilization, relatively small proportions of N (10 – 13 %) and P (33 – 43 %) are probably lost with senescent leaf whorls, while there is complete loss of all Ca, K, and Mg. The total content of starch and free sugars was 26 – 47 % DM along adult shoots, with the maximum in the 7^th – 10^th whorls. About 30 % of the total maximum sugar content was probably lost with dead whorls. The plant was found to take up 5 – 7 times more NH₄ ⁺ to NO₃ ^– from a mineral medium. Under nearly-natural conditions in an outdoor cultivation container, catching of prey led to significantly more rapid growth than in unfed plants. DM of the fed controls was 48 % higher than in the unfed plants. The controls produced 0.69 branches per plant, while the unfed plants did not produced any. However, the N and P content per DM unit increased by 6 – 25 % in the apices and the first 6 whorls in the unfed variant, as compared to the fed controls. It may be suggested that carnivory is very important for Aldrovanda.