Effects of Bean Leaf Age on Pathogenicity by Botrytis fabae

Leaves from field bean plants grown out of doors were inoculated with conidia of B. fabae immediately after detaching from stems. The oldest leaves developed more lesions than youngest ones, although they were not chlorotic. On intact plants at high humidities, established lesions on young leaves increased in size at only half the rate of those on old. but still green leaves. Seven days after inoculation a higher proportion of lesions on old leaves bore conidia than those on young leaves, but leaf age had no significant effect on numbers of conidia per mm² of lesion area. Young leaflets from bean plants grown in a controlled environment or in the field challenged with β. cinerea accumulated more phytoalexins than did old ones.     

The transformation of local lesion counts for statistical analysis

An analysis of the frequency distribution of local lesions, produced by viruses on half-leaves of a number of plants, shows that their standard error increases with increasing mean. Hence analysis of variance and statistical tests of significance should not be applied to lesion numbers unless they are suitably transformed. The transformation into logarithms over-corrects so that the standard error decreases with increasing mean. A satisfactory transformation is y = log₁₀ ( x + c ), where x is the number of lesions and c is a constant. A method is given of assessing c for different experiments. Great accuracy is not needed; in an experiment discussed in detail a satisfactory transformation is obtained with any value for c between 15 and 80.
On individual plants the numbers of lesions formed on half-leaves are distributed more or less normally, whereas their distribution about the common mean for many plants is skew and 'leptokurtic'. The distribution of the transformed numbers is almost normal, both for individual plants and about the common mean for a number of plants.     

LEAF INFECTION OF COTTON BY XANTHOMONAS MALVACEARUM (E.F.SM.) DOWSON

Xanthomonas malvacearum spread more rapidly along vascular tissue than into mesophyll when inoculated to the main veins of susceptible cotton leaves. The extent of spread varied with the concentrations of inocula, tissue age and cotton variety.
Increasing concentrations of inocula accelerated the initial spread of disease.
Bacteria spread more rapidly in young leaves than in old—increasing age greatly decreased disease in the mesophyll. The initial invasion was quicker in young leaves of young plants than in young leaves of old plants.
Three types of behaviour, according to the host's reaction, distinguish Knight's resistance factors: ( a ) where X. malvacearum spread extensively along veins and into mesophyll of plants containing factors B₃ and B₅; ( b ) where it was restricted to the point of inoculation in plants containing B ₄, B₉ and combinations with B _6m; and ( c ) where it spread along veins but not appreciably into mesophyll in varieties containing B ₂ and B ₂ B ₃.
From this and four other different types of tests, factors B ₂ and B ₃ seem to increase mesophyll resistance but only B ₂ gives appreciable vascular resistance. Further, the vascular bundles in varieties with B ₂ seem to be surrounded by an additional 'barrier' which resists X. malvacearum.     

Effect of high external NaCl concentrations on ion transport within the shoot of Lupinus albus. I. Ions in xylem sap

Abstract. Xylem sap was collected from individual leaves of intact transpiring lupin plants exposed to increasing concentrations of NaCl by applying pneumatic pressure to the roots. Concentrations of Na⁺ and Cl⁻ in the xylem sap increased linearly with increases in the external NaCl concentration, averaging about 10% of the external concentration. Concentrations of K⁺ and NO₃⁻, the other major inorganic ions in the sap, were constant at about 2.5 and 1.5 mol m⁻³, respectively. There was no preferential direction of Na ⁺ or Cl⁻ to either young or old leaves: leaves of all ages received xylem sap having similar concentrations of Na⁺ and Cl⁻, and transpiration rates (per unit leaf area) were also similar for all leaves. Plants exposed to 120–160 mol m⁻³ NaCl rapidly developed injury of oldest leaves; when this occurred, the Na⁺ concentration in the leaflet midrib sap had increased to about 40 mol m⁻³ and the total solute concentration to 130 osmol m⁻³. This suggests that uptake of salts from the transpiration stream had fallen behind the rate of delivery to the leaf and that salts were building up in the apoplast.     

Effect of competition and leaf age on visible and infrared reflectance in pine foliage

Abstract. The effect of plant competition on spectral reflectance in the 400–2500 nm wavelength region was determined for 3-month-old and 15-month-old leaves of loblolly pine ( Pinus taeda L.). Strong competition decreased water potentials and Mg concentrations, and increased K in young and old leaves. Also, competition decreased Ca and total chlorophyll in young leaves. As measured with a scanning radiometer, reflectance in young leaves at 551 nm decreased from 20 to 14% as water potentials increased from -2.2 to -0.9 MPa (r²= 0.82). For young and old leaves reflectance at 551 nm decreased from 20 to 10% with increasing total chlorophyll (r²= 0.64). Reflectance decreased slightly with increasing K in young leaves (401 nm, r²= 0.55), and with increasing Mg in old leaves (470 nm, r²= 0.57). Increased visible reflectance under strong competition may have resulted primarily from decreased water potentials. Reflectances were much greater in young versus old leaves in the 750–1300 nm range, and were greater in old rather than young leaves from 1400–2500 nm. Infrared reflectances were not, however, significantly affected by competition.     

Contrasting effects of simazine on the photosynthetic physiology and leaf morphology of two Populus clones

Differential effects of simazine (2-chloro-4,6-bis(ethylamino)- s -triazine) on the physiology of two Populus clones were investigated in a greenhouse study. Additions of 5 mg/pot simazine to young plants had no deleterious morphological or physiological effects on clone NC 5328 ( P. x euramericana cv. I 45/51; Section Aigeiros), but reduced the rate of CO₂ fixation, increased CO₂ compensation concentrations and lowered the specific leaf weight of clone NE 388 ( P. maximowiczü x P. trichocarpa cv. Kingston; section Tacamahaca). Abaxial leaf conductance to water vapor was not affected in NE 388. Deleterious effects of simazine on NE 388 were detected ca 48 h after exposure of plants to simazine and generally became more pronounced thereafter. Visual symptoms of injury were evident at ca 2 weeks after simazine application.
Toxic responses to simazine in clone NE 388 varied in different portions of the crown. Inhibition of photosynthesis and increased CO₂ compensation concentrations were more pronounced in the region of recently matured leaves, but were somewhat less in the region of expanding leaves. Older mature leaves in the lower crown region showed no visual symptoms of injury and the rate of photosynthesis and CO₂ compensation concentrations were largely unaffected.     

Distribution of 14C assimilates in the storage root of sugar beet plants after import from leaves of different age

In the sugar beet plant ( Beta vulgaris L. ssp. altissima ) the vascular bundles of old leaves lead to the center and those of young leaves to the periphery of the storage root. Whether the flux of assimilates follows these anatomical routes was tested by applying ¹⁴CO₂ for 4 h to either an old (10th) or a young (20th) leaf in intact sugar beet plants. Four-month-old plants, which had about 30 leaves, were used in the experiment. The ¹⁴C distribution in the storage root was measured by autoradiography and counting in about 20 cross and longitudinal sections per root.
About 37% of assimilated ¹⁴C from an old leaf and 23% from a young leaf were exported within 24 h. Although some ¹⁴C moved into younger leaves, most was exported into the storage root. During its rapid movement towards the root tip, which took place perferentially in the orthostichon belonging to the [¹⁴C]-treated leaf, the label spread laterally.
The autoradiograms indicate that the distribution of assimilates within the storage root is roughly determined by the course of the vascular bundles extending from the source leaf. The fine distribution, however, seems to be controlled by sucrose gradients between storage cells.     

Sodium partitioning within the shoot of soybean

Uptake and partitioning of Na⁺ and Cl⁻ in plants of soybean ( Glycine max L. Merr. cv. Hodgson) exposed to moderate NaCl concentrations were studied over an 8-day period. Plants showed marked retention of Na⁺ in the stems and low transport to laminae of young leaves. The xylem sap ascending the main axis was progressively depleted in Na⁺. The oldest leaf greatly contributed to Na⁺ depletion of the sap flowing to younger leaves. These results in combination with estimates of phloem recirculation indicated that Na⁺ accumulation in the young leaf was prevented both by depletion of Na⁺ from the xylem stream, and by a high recirculation of Na⁺ via the phloem. However, this protection of young leaves was effective only for very mild salinity treatment.     

Accumulation of a 22-kDa protein and its mRNA in the leaves of Raphanus sativus in response to salt stress or water deficit

The response of 10-day-old seedlings of Raphanus sativus L. cv. Fakir to salt stress (100 m M to 200 m M NaCl) was investigated. Three weeks after initiation of salt treatment, the fresh weight of the shoots of salt-treated plants was half that of untreated plants. The salt stress resulted in the accumulation of Na⁺, preferably in the old leaves. The K⁺ level was reduced by as much as 50% in the old leaves of NaCl-treated plants, whereas this reduction was only 20–25% in the young leaves. Free proline accumulated in all aerial organs, and the highest levels were found in the young leaves. Patterns of total proteins extracted from the leaves of control or salt-treated plants were compared. The most obvious change concerned a 22-kDa, pl 7.5 polypeptide, which accumulated after exposure of the plants to NaCl. The appearance of this polypeptide was also mediated by a rapid drought stress, and sequencing indicated that it is related to the Künitz protease inhibitor family. A cDNA clone corresponding to the radish 22-kDa polypeptide was obtained and sequenced. Northern blot analysis showed that salt stress induces a large accumulation of this mRNA in the leaves of radish.     

sse of photosynthetic parameters for the diagnosis of copper deficiency in Pinus radiata seedlings

Six-month-old water cultures of Pinus radiataI D. Don seedlings showed optimal growth, and the highest CO₂ assimilation and photosystem I-dependent ascorbate/dichlorophenolindophenol → NADP⁺ electron flow, at 3.0 uM Cu²⁺ (excess) in the hydroponic media. In the nine-month-old water cultures, when the early Cu deprivation has been overcome, the optimum for plant growth and CO₂ fixation shifts to 0.3 u M Cu²⁺ (normal); at that time, the 3.0 uM Cu²⁺ water cultures showed toxic symptoms of foliar chlorosis. Under Cu²⁺ deficient levels (0.03 uM) a clear decrease in the photosystem I-linked electron transport and CO₂ assimilation rates, as well as in the whole plant development, could be observed. Both six- and nine-month-old water cultures showed a close relationship between the Cu²⁺ concentration of the media and the foliar Cu content. However, leaf chlorophyll and the Cu content of thylakoid lamellae showed such a correlation only in the Cu²⁺ deficient and Cu²⁺ normal water cultures. The conclusion from these results is that the electron transport rate ascorbate/dicblorophenolindophenol → NADP⁺, and the Cu content of the photosynthetic membranes, can be used to diagnose a Cu deficiency in Pinus radiata plants.     

Inhibition of photosynthesis and export in geranium grown at two CO2 levels and infected with Xanthomonas campestris pv. Pelargonii

The effects of CO₂ enrichment on growth of Xanthomonas campestris pv. pelargonii and the impact of infection on the photosynthesis and export of attached, intact, 'source' leaves of geranium ( Pelargonium x domesticum, 'Scarlet Orbit Improved' ) are reported. Two experiments were performed, one with plants without flower buds, and another with plants which were flowering. Measurements were made on healthy and diseased leaves at the CO₂ levels (35 Pa or 90 Pa) at which the plants were grown. There were no losses of chlorophyll, or any signs of visible chlorosis or necrosis due to infection. Lower numbers of bacteria were found in leaves at high CO₂, suggesting growth at elevated CO₂ created a less favourable condition in the leaf for bacterial growth. Although high CO₂ lowered the bacterial number in infected leaves, reductions in photosynthesis and export were greater than at ambient CO₂. The capacity of infected source leaves to export photoassimilates at rates observed in the controls was reduced in both light and darkness. In summary, the severity of infection on source leaf function by the bacteria was increased, rather than reduced by CO₂ enrichment, underscoring the need for further assessment of plant diseases and bacterial virulence in plants growing under varying CO₂ levels.     

Effect of high external NaCl concentration on ion transport within the shoot of Lupinus albus. II. Ions in phloem sap

Abstract. Phloem sap was collected from petioles of growing and fully expanded leaves of lupins exposed to 0–150 mol m⁻³ [NaCl]_ext, for various periods of time. Sap bled from growing leaves only after the turgor of the shoot was raised by applying pneumatic pressure to the root. Increased pressure was also needed to obtain sap from fully expanded leaves of plants at high [NaCl]_ext. Exposure to NaCl caused a rapid rise in the Na⁺ concentration in phloem sap to high levels. The Na⁺ concentration reached 20 mol m⁻³ within a day of exposure and reached a plateau of about 60 mol m⁻³ in plants at 50–150 mol m⁻³ [NaCl]_ext, after a week. There was a slower, smaller increase in the Cl⁻ concentration. K⁺ concentrations in phloem sap were not affected by [NaCl]_ext. Cl⁻ concentrations in phloem sap collected from growing leaves were similar to those from old leaves while Na⁺ concentrations were somewhat increased, suggesting that there was no reduction in the salt content of the phloem sap while it flowed within the shoot to the apex. Calculations of ion fluxes in xylem and phloem sap indicated that Na⁺ and Cl⁻ fluxes in the phloem from leaves of plants at high NaCl could be equal to those in the xylem. This prediction was borne out by observations that Na⁺ and Cl⁻ concentrations in recently expanded leaves remained constant.     

Effects of cadmium on growth of Helianthus annuus seedlings: physiological aspects

Sunflower seedlings ( Helianthus annuus hybrid Select) were grown in a complete nutrient solution in the absence or presence of Cd²⁺ (10 and 20 μM). Analyses were performed to establish whether there was a differential effect of Cd²⁺ on mature and young leaves. After 7 d the growth parameters as well as the leaf area had decreased in both mature and young leaves. Accumulation of Cd²⁺ in the roots exceeded that in the shoots. Seedlings treated with Cd²⁺ exhibited reduced contents of chlorophyll and CO₂ assimilation rate, with a greater decrease in young leaves. The photochemical efficiency of photosystem II (PSII) was not altered by Cd²⁺ treatment in either mature or young leaves, although during steady-state photosynthesis in young leaves there was a significant alteration in the following parameters: quantum yield of electron transport by PSII (Φ_PSII), photochemical quenching ( q _P), non-photochemical quenching ( q _NP), and excitation capture efficiency of PSII (Φ_exc).     

Production and Pathogenicity to Wheat of Pseudocercosporella herpotrichoides Conidia

Weekly estimates of numbers of Pseudocercosporella herpotrichoides conidia on naturally infected wheat straw, made from February to July 1982, showed there were most conidia (8.1 × 10⁶ per straw) in February and least (1.9 × 10⁴ per straw) at the end of June. The viability of these spores remained high throughout this period, with an average of 85 % germination after 24 h.
After removal of spores produced in the field, straws were incubated at 5, 10, 15, 20 or 25°C and subsequent sporulation assessed after 3 or 5 weeks. The optimum temperature for spore production was 5°C and very few spores were produced at 25°C. There was no difference in viability between spores produced at different temperatures.
Wheat seedlings placed amongst infected straw collected and retained spores on the upper and lower surfaces of all leaf blades and on outer leaf sheaths. Both naturally dispersed spores and spores sprayed on to plants were not removed by subsequent rainfall.
When wheat seedlings were inoculated between the coleoptile and outer leaf sheath with different numbers of P. herpotrichoides spores, lesion development was most rapid in seedlings inoculated with the greatest numbers of spores. However, after incubation for 12 weeks visible lesions were present on all plants inoculated with > c. 10 spores.     

NaCl-induced accumulation of tonoplast and plasma membrane H+-ATPase message in tomato

NaCl-induced changes in the accumulation of message for the 70 kDa subunit of the tonoplast H⁺-ATPase and plasma membrane H⁺-ATPase were studied in hydroponically grown plants of Lycopersicon esculentum Mill. cv. Large Cherry Red. There was increased accumulation of message for the 70 kDa (catalytic) subunit of the tonoplast H⁺-ATPase in expanded leaves of tomato plants 24 h after final NaCl concentrations were attained. This was a tissue-specific response; levels of this message were not elevated in roots or in young, unexpanded leaves. The NaCl-induced accumulation of this message was transient in the expanded leaves and returned to control levels within 7 days. The temporal and spatial patterns of NaCl-induced accumulation of message for the plasma membrane H⁺-ATPase differed from the patterns associated with the 70 kDa subunit of the tonoplast H⁺-ATPase. NaCl-induced accumulation of the plasma membrane H⁺-ATPase message occurred in both roots and expanded leaves. Initially accumulation of the plasma membrane H⁺-ATPase message was greater in root tissue than in expanded leaves, but increased to higher levels in expanded leaves after 7 days. These results suggest that increased expression of the tonoplast H⁺-ATPase is an early response to salinity stress and may be associated with survival mechanisms, rather than with long-term adaptive processes.     

Regulation of the photosynthetic capacity of primary bean leaves by the red:far-red ratio and photosynthetic photon flux density of incident light

The main objective of the present work was to examine the effects of the red:far-red ratio (R:FR) prevailing during leaf development on the photosynthetic capacity of mature leaves. Plants of Phaseolus vulgaris L. cv. Balin de Albenga were grown from time of emergence in a controlled environment room, 25 ± 3°C, 12-h photoperiod, with different light treatments:a) high photosynthetic photon flux density (PPFD) = 800 μmol m⁻¹ s⁻¹+ high R:FR= 1.3;b) low PPFD= 300 μmol m⁻² s⁻¹+ high R:FR= 1.3; c) high PPFD=800 μmol m⁻² s⁻¹+ low R:FR= 0.7; d) low PPFD= 300 μmol m⁻²s⁻¹+ low R:FR=0.7. With an R:FR ratio of 1.3, a decrease in irradiance during leaf growth reduced photosynthesis when measured at moderate to high PPFD; but when measured at low PPFD, leaves expanded under low irradiance actually had photosynthesis rates higher than those of leaves grown in high irradiance. A low R:FR ratio during development reduced the photosynthetic capacity of the leaves. In leaves expanded under R:FR = 0.7 and high irradiance photosynthesis was reduced by 42 to 89%, depending on the PPFD at which measurements were made, whereas for leaves developed at R:FR = 0.7 and low irradiance photosynthesis decreased by 21 to 24%, compared to leaves under R:FR = 1.3 and similar irradiance. The reduced photosynthetic capacity under R:FR = 0.7 and high irradiance. In natural environments, leaves may experience low R:FR conditions temporarily during their development, and this may affect their future photosynthetic capacity in full sunlight.     

Reduced Development of Grey Mould (Botrytis cinerea) in Bean and Tomato Plants by Calcium Nutrition

Fertilization of bean plants grown in perlite with 1 and 3 mM CaCl₂ or Ca(NO₃)₂ reduced severity of grey mould as compared with control plants or plants fertilized with 5 mM of the compounds. Fertilization with Ca(NO₃)₂ reduced severity leaf grey mould and fruit ghost spots of tomato plants grown in perlite by 70 and 45%, respectively. The rate of decrease varied with the position of the fruits on the plants. Leaves from plants treated with calcium or otherwise [KNO₃, (NH₄)₂SO₄] produced less ethylene than leaves of nontreated plants. Rate of growth of B. cinerea was lower on growth medium prepared from washings from leaves of calcium fertilized plants than from leaves from other treatments. The fertilizer combination Ca(H₂PO₄)₂+ CaSO₄ (1 and 3 g/kg soil) applied once to tomato plants grown in soil reduced severity of leaf grey mould by 80 % (significant at P = 0.05) but 1–3 g CaSO₄/kg soil only tended to reduce disease severity (30–40 %, not significant) as compared with the control. The compounds CaCl₂ and Ca(NO₃)₂ increased significantly ( P = 0.05) the growth of B. cinerea on synthetic medium when applied at rates of 1 0–10.0 mM whereas reduction of growth was observed with 0.1 mM of the compounds and of CaSO₄.     

Salt tolerance in the halophyte Suaeda maritima (L.) Dum. The influence of the salinity of the culture solution on leaf starch and phosphate content

Abstract. The starch concentration in mature leaves of the halophyte Suaeda maritima increased from 4.7 to 7.3 mg mg⁻¹ chlorophyll when sodium chloride (680 mol M⁻³) was added to the solution in which the plants were grown. This effect of salinity on the starch: chlorophyll ratio was greater in young than in old leaves. Electron micrographs showed the starch to be in the chloroplasts and this was confirmed by measurements on isolated chloroplasts. Total phosphorus concentration (mg mg⁻¹ chlorophyll) in leaves of all ages from plants of S. maritima decreased on salinization of the growth medium suggesting an inverse relationship between phosphorus and starch concentrations. However, although leaf starch concentration varied with leaf age, phosphorus concentration did not. The cause of starch accumulation in chloroplasts at salinities which are optimal for growth (340 mol m⁻³) remains unclear.     

Water translocation in Kalanchoë daigremontiana during periods of drought

Abstract. Kalanchoë daigremontiana strongly reduced daily water loss within 6 d of drought using CAM to restrict transpiration and net CO₂ uptake to the dark period.
Water translocation from old to young leaves of the plant was an additional mechanism which reduced the negative effects of drought on the water relations of young leaves. Excision of old leaves after 7–9 d of drought resulted in a decrease in the water content of young leaves. This was observed despite a decrease in transpirational water loss from young leaves. Water content in young leaves increased slightly in plants with all their leaves in place.
The dry weight of young leaves clearly increased during the experimental period when old leaves were present, but it remained relatively constant in plants without old leaves. Obviously, in addition to water, solutes were transported from old to young leaves of the plant via the phloem. Xylem tension was higher in young compared to old leaves; thus, water translocation could have occurred via xylem elements.
Since transport of organic matter in the phloem is also linked to water flow, phloem transport additionally may contribute effectively to the balance of the water budget in young leaves.