Inhibition of sulphur redistribution into new leaves of vegetative soybean by excision of the maturing leaf

When soybean plants are pulsed with [³⁵S]sulphate, label is subsequently redistributed from the roots to the leaves. This confounds studies to measure the redistribution of label from leaves. Accordingly, soybean plants ( Glycine max [L.] Merr. cv. Stephens) were grown in 20 μ M sulphate and a small portion of the root system (donor root) was pulsed with [³⁵S]sulphate for 24 h. After removing the donor root, the plants were transferred into unlabelled solution, either without sulphate (S20→SO) or with 20 μ M sulphate (S20→20) (intact plants). Also at this time, the expanding leaf (L3) was excised from half of the plants in each treatment (excised plants). Immediately after the pulse, only ca 15% of the label occurred in the roots and ca 40% in the expanding leaf, L3, mostly in the soluble fraction. In intact S20→20 plants, ³⁵S-label was exported from the soluble fraction of L3, mostly as sulphate, whilst L4 and L5 imported label. Similar responses occurred in S20→SO plants except that export of label from L3 was more rapid. Excision of L3 from S20→S20 plants inhibited labelling of leaves L4-L6 but not total sulphur, whereas in S20→SO plants, excision of L3 inhibited the import of both total sulphur and ³⁵S-label in leaves L4, L5 and L6. The data suggest that the soluble fraction of almost fully expanded leaves is an important reserve of sulphur for redistribution to growing leaves. The ³⁵S-label in the root system exhibited fluctuations consistent with its proposed role in the recycling of soluble sulphur from the leaves.     

Distribution and redistribution of sulphur taken up from nutrient solution during vegetative growth in barley

Barley plants were grown in a nutrient solution containing 25 μ M sulphate and the roots were pulsed with [³⁵S]sulphate for 48-h periods at 6 different times between the emergence of leaf 5 (L5) and the emergence of leaf 8 (L8). Growth was continued in unlabelled solution until the emergence of L10. Within the shoot system sulphur was directed principally into the leaf undergoing expansion. A large proportion of the ³⁵S-label delivered to young expanding leaves (> 40% of full expansion) did not occur at the time of the pulse, but subsequently during the ensuing chase indicating slow redistribution of sulphur from another site. During the later stages of leaf expansion (40–100%), most of the sulphur entered the leaf during the pulse, suggesting that sulphur was delivered more directly from the nutrient solution. Up to 75% of the sulphur delivered to L3–L6 at the time they approached or attained full expansion (70–100%) was re-exported. At least some of the sulphur exported from fully expanded leaves was redistributed to developing leaves.     

Mobilization of sulphur in soybean cotyledons during germination

Soybean seeds ( Glycine max L. cv , Stephens) contain a large amount of sulphur (ca 40 μ mol seed⁻¹), mostly in the insoluble fraction in the cotyledons. During germination in nutrient solution lacking sulphur the amount of insoluble sulphur decreases to very low levels. This is accompanied by a transitory increase in the pool of soluble sulphur which then declines. All of the sulphur lost from the cotyledons is quantitatively recovered in the seedling. In the short term, the root and the stem are the most important sinks for sulphur from the cotyledons but as growth proceeds the shoot becomes the dominant sink for remobilized sulphur. Within the shoot most of the sulphur is recovered in leaves L1 and L2. The growth of L3 and, to a lesser extent, L2, was retarded due to sulphur insufficiency. The cotyledons of plants treated with 20 μ M sulphate also exhibited mobilization of sulphur from the insoluble fraction except that the maximum rate of loss of sulphur occurred somewhat later. Plants grown with sulphate exhibited a net gain of sulphur and did not exhibit sulphur insufficiency. In these plants, endogenous sulphur from the cotyledons was directed into L1–L3 and this sulphur remained within these leaves for the duration of the experiment. The delivery of exogenous sulphur (supplied as [³⁵S]sulphate via the roots) to the leaves increased with leaf number. In leaves L1–L3, the level of exogenous sulphur in any one leaf declined with time, indicating that this sulphur was remobilized and did not mix with the sulphur derived from the cotyledons. It was concluded that the cotyledons are an important source of sulphur to support early plant growth and development of soybean.     

Sulphur nutrition changes the sources of S in vegetative tissues of wheat during generative growth

During generative growth, developing wheat grains require nitrogen and sulphur to synthesize storage proteins. The hypothesis that the S required for grain growth can be derived from vegetative tissues was examined by growing plants in nutrient culture containing either 50 M S (low-S) or 200 M S (high-S) and terminating the nutrient supply at various times during generative growth. After terminating the nutrient supply, high-S plants redistributed soluble S to developing grains from pools in roots and leaves, whereas low-S plants remobilized insoluble S (protein-S) from the leaves to the grains. A model for the cycling of S within mature leaves during generative growth is presented.     

Phenology of nutritional differences between new and mature leaves and its effect on caterpillar growth

Abstract. 1. We determined the phenology of the shrub Spiraea latifolia Ait. Bork. (Rosaceae), which has indeterminate shoot growth, and the effects of phenological changes in leaf quality on growth rate of the early-spring feeding buckmoth caterpillars, Hemileuca lucina Hy. Edw. (Saturniidae).
2. Leaves, regardless of whether they were newly expanded or several weeks old, were tougher later in the growth season (mid-June) than similarly aged leaves collected earlier; correspondingly, water and nitrogen content for leaves of all ages declined through the larval period. By July, newly expanded leaves had no more nitrogen than mature leaves.
3. Relative growth rate of third instar larvae fed new leaves or a mixture of new and mature leaves in early June was higher than that of those fed mature leaves, and efficiency of conversion of digested food to biomass was higher for larvae fed new leaves than for those fed mature leaves or a mixture.
4. In another experiment, larvae were reared on new leaves through the fourth instar and then fed a diet of new, mature or a combination of new and mature leaves, a regimen that was similar to the phenologies of both plants and caterpillars in the field. There was no difference in time to pupation or pupal weights among these treatments.     

The influence of ancymidol on morphology,anatomy, and chlorophyll levels in developing and mature Helianthus annuus leaves

Ancymidol foliar spray at 132 mg·liter^–1 a.i. modified leaf anatomy of developing Helianthus annuus L. Mammoth Russian leaves, but not of mature leaves. Ancymidol was effective in retarding plant growth when applied at the young seedling or at a more mature stage of growth. Ancymidol increased leaf weight per unit area and chlorophyll content on an area and unit weight basis, regardless of stage of leaf development. Total chlorophyll per leaf was also increased in mature leaves. Thus, darker green foliage due to increased chlorophyll content and modified leaf anatomy responses were determined to be independent effects.Texas Agricultural Experiment Station paper no. 22927.     

Using a biochemical C4 photosynthesis model and combined gas exchange and chlorophyll fluorescence measurements to estimate bundle-sheath conductance of maize leaves differing in age and nitrogen content

Bundle-sheath conductance (g(bs) ) affects CO(2) leakiness, and, therefore, the efficiency of the CO(2) -concentrating mechanism (CCM) in C(4) photosynthesis. Whether and how g(bs) varies with leaf age and nitrogen status is virtually unknown. We used a C(4) -photosynthesis model to estimate g(bs) , based on combined measurements of gas exchange and chlorophyll fluorescence on fully expanded leaves of three different ages of maize (Zea mays L.) plants grown under two contrasting nitrogen levels. Nitrogen was replenished weekly to maintain leaf nitrogen content (LNC) at a similar level across the three leaf ages. The estimated g(bs) values on leaf-area basis ranged from 1.4 to 10.3 mmol m(-2) s(-1) and were affected more by LNC than by leaf age, although g(bs) tended to decrease as leaves became older. When converted to resistance (r(bs) = 1/g(bs)), r(bs) decreased monotonically with LNC. The correlation was presumably associated with nitrogen effects on leaf anatomy such as on wall thickness of bundle-sheath cells. Despite higher g(bs), meaning less efficient CCM, the calculated loss due to photorespiration was still low for high-nitrogen leaves. Under the condition of ambient CO(2) and saturating irradiance, photorespiratory loss accounted for 3-5% of fixed carbon for the high-nitrogen, versus 1-2% for the low-nitrogen, leaves.     

Responses of Vigna radiata to Foliar Application of 28-Homobrassinolide and Kinetin

Effects of 28-homobrassinolide (HBR) and kinetin (KIN) on photosynthesis, nitrogen metabolism, and the seed yield were studied. The leaves of 25-d-old plants of Vigna radiata (L.) Wilczek were sprayed with 0.01, 1.0 or 100 M aqueous solution of KIN, or 0.0001, 0.01 or 1.0 M that of HBR. KIN and especially HBR increased the activities of nitrate reductase and carbonic anhydrase, chlorophyll and total protein contents and net photosynthetic rate in the leaves, and pod number and seed yield, at harvest.     

Influence of soil drying on root development,water relations and leaf growth of Ceratonia siliqua L.

Summary Seedlings of Ceratonia siliqua L., an evergreen sclerophyll species native to the Mediterranean region, were grown in 30-cm deep tubes of John Innes II potting compost in a growth cabinet maintained at 15° C during a 12-h day where PAR was 400 mol m^–2 s^–1. After a period of acclimatisation to the conditions in the cabinet during which plants were watered every day, water was withheld from the soil in some tubes for 24 days. These conditions may be regarded as a simulation of the natural situation. Estimates of leaf and root water potential and solute potential, leaf growth and root development were made at intervals during the soil drying cycle on both watered and unwatered plants. Water potential and solute potential measurements were made both on young expanding and on fully expanded leaves. During the experimental period, root growth of C. siliqua was not much affected by soil drying, and roots in both the watered and the unwatered columns penetrated to the bottom of the soil tubes by the end of the drying treatment. Expanded leaves showed significant limitation in stomatal conductance as soil drying progressed. Leaf water potential of fully expanded leaves of unwatered plants declined substantially. In contrast, water potential of young expanding leaves on unwatered plants declined to only a limited extent and turgor was sustained. As the soil dried, stomatal conductance of young leaves was always higher than that of mature leaves; also, placticity and elasticity of young leaves slowly decreased whereas mature leaves became stiff. Changing leaf cell wall properties may determine different patterns of water use as the leaves age. A mechanism of continuous diffusion of water through the soil towards the tip and pumping towards the young leaves is proposed.     

Morphophysiological Indices of the Source Leaf in Wheat Plants Acclimated to Conditions of Nitrogen Nutrition

Growth, leaf and cell morphology, and the chemical composition of the second leaf were studied in wheat (Triticum aestivumL., cv. Inna) plants grown on the medium containing nitrate, ammonium, or no nitrogen at all. Independent of the nitrogen nutrition, the second leaf of the 21-day-old plants matures and functions as a source of assimilates. Both ammonium nutrition and nitrogen deficiency decreased the fresh weight, area, and cell size in the leaf; however, the conditions of nitrogen nutrition did not affect the dry weight of the leaf. Nitrogen starvation increased and ammonium nutrition decreased the relative content of the cell walls in the dry weight. In the nitrate-fed plants, the leaf content of sucrose increased, and the contents of reduced nitrogen (N_red) and protein were lower than in the ammonium treatment. Reciprocally, the contents of reduced nitrogen and protein were highest in the ammonium treatment, the content of sucrose was lowest, with starch practically absent from the leaf. The nitrogen-starved leaf accumulated a large amount of starch, the N_redcontent was two times lower than in the ammonium-fed plants, and the protein content was similar to that in the nitrate-fed plants. Thus, leaf and cell morphology and the content of N_red, protein, and carbohydrate changes in different ways during wheat acclimation to the condition of nitrogen nutrition. By assessing the cell wall weight, the authors established that, depending on nitrogen nutrition, this cell compartment accepts a variable flow of carbon.     

Diurnal changes in sucrose phosphate synthase activity in leaves

Studies were conducted to identify and compare diurnal changes in sucrose phosphate synthase (EC 2.4.1.14) activity in leaves of different species, and the effect of nitrogen nutrition on the rhythm in soybean [ Glycine max (L). Merr] leaves. In recently expanded corn ( Zea mays L.) leaves, a single peak of enzyme activity was observed at the beginning of the photoperiod. A similar pattern was observed in older corn leaves, but activities (leaf fresh weight basis) were lower. In recently expanded pea ( Pisum sativum L.) and soybean leaves, two peaks of sucrose phosphate synthase activity were observed over a 24-h light:dark period, one at the beginning and one at the end of the photoperiod. A similar pattern was observed in older soybean leaves, but activities were generally lower and the amplitude of the changes was reduced. In a separate experiment, soybean plants were grown in the greenhouse with either 2 or 10 m M nitrate. The high-N plants had higher rates of photosynthesis and translocation, and greater activities of sucrose phosphate synthase in leaf extracts, compared to low-N plants. Over both experiments with soybeans, changes in sucrose phosphate synthase activity during the photoperiod were closely aligned with changes in translocation rate.     

Effects of leaf age,nitrogen nutrition and photon flux density on the distribution of nitrogen among leaves of a vine (Ipomoea tricolor Cav.) grown horizontally to avoid mutual shading of leaves

Effects of leaf age, nitrogen nutrition and photon flux density (PFD) on the distribution of nitrogen among leaves were investigated in a vine, Ipomoea tricolor Cav., which had been grown horizontally so as to avoid mutual shading of leaves. The nitrogen content was highest in newly developed young leaves and decreased with age of leaves in plants grown at low nitrate concentrations and with all leaves exposed to full sunlight. Thus, a distinct gradient of leaf nitrogen content was formed along the gradient of leaf age. However, no gradient of leaf nitrogen content was formed in plants grown at a high nitrate concentration. Effects of PFD on the distribution of nitrogen were examined by shading leaves in a manner that simulated changes in the light gradient of an erect herbaceous canopy (i.e., where old leaves were placed under increasingly darker conditions with growth of the canopy). This canopy-type shading steepened the gradient of leaf nitrogen content in plants grown at a low nitrogen supply, and created a gradient in plants grown at high concentrations of nitrate. The steeper the gradient of PFD, the larger the gradient of leaf nitrogen that was formed. When the gradient of shading was inverted, that is, younger leaves were subjected to increasingly heavier shade, while keeping the oldest leaves exposed to full sunlight, an inverted gradient of leaf nitrogen content was formed at high nitrate concentrations. The gradient of leaf nitrogen content generated either by advance of leaf age at low nitrogen availability, or by canopy-type shading, was comparable to those reported for the canopies of erect herbaceous plants. It is concluded that both leaf age and PFD have potential to cause the non-uniform distribution of leaf nitrogen. It is also shown that the contribution of leaf age increases with the decrease in nitrogen nutrition level.     

Vegetative phase change in Metrosideros: Shoot and root restriction

Plants of Metrosideros excelsa Sol. ex Gaertn. Scarlet Pimpernel, which had undergone reversal of ontogenetic ageing (rejuvenation) following micropropagation, were subjected to shoot and root restriction treatments over 35 weeks to accelerate vegetative phase change. Shoot restriction was imposed by removal of axillary branches, while control plants were allowed to branch. Root restriction, imposed by growing plants in a range of container sizes, was applied in factorial combination with shoot restriction. Image analysis techniques were used to measure changes in leaf dimensional (roundness, area, length, width, length/width ratio and perimeter) and optical (hue, saturation and lightness) properties which change gradually between juvenile and mature forms of Metrosideros excelsa. Leaves of single-stemmed plants became progressively mature with increasing node position, and developed the downy tomentum on the abaxial surface characteristic of mature leaves. In general, leaves on the branched plants did not become progressively mature with increasing node position. The acceleration in vegetative phase change in single-stemmed plants was not due to a greater number of nodes produced along the main axis, nor because of a greater distance from root to shoot apex. Root restriction reduced root growth in branched plants, and increased shoot/root dry weight ratio in both sets of plants. However, it did not affect shoot growth, nor did it accelerate vegetative phase change.     

Hydraulic connections of leaves and fruit to the parent plant in Capsicum frutescens (hot pepper) during fruit ripening

Background and Aims

The hydraulic architecture and water relations of fruits and leaves of Capsicum frutescens were measured before and during the fruiting phase in order to estimate the eventual impact of xylem cavitation and embolism on the hydraulic isolation of fruits and leaves before maturation/abscission.

Methods

Measurements were performed at three different growth stages: (1) actively growing plants with some flowers before anthesis (GS1), (2) plants with about 50 % fully expanded leaves and immature fruits (GS2) and (3) plants with mature fruits and senescing basal leaves (GS3). Leaf conductance to water vapour as well as leaf and fruit water potential were measured. Hydraulic measurements were made using both the high-pressure flow meter (HPFM) and the vacuum chamber (VC) technique.

Key Results

The hydraulic architecture of hot pepper plants during the fruiting phase was clearly addressed to favour water supply to growing fruits. Hydraulic measurements revealed that leaves of GS1 plants as well as leaves and fruit peduncles of GS2 plants were free from significant xylem embolism. Substantial increases in leaf petiole and fruit peduncle resistivity were recorded in GS3 plants irrespective of the hydraulic technique used. The higher fraction of resistivity measured using the VC technique compared with the HPFM technique was apparently due to conduit embolism.

Conclusions

The present study is the first to look at the hydraulics of leaves and fruits during growth and maturation through direct, simultaneous measurements of water status and xylem efficiency of both plant regions at different hours of the day.     

Leaf age and salinity influence water relations of pepper leaves

Plant growth is reduced under saline conditions even when turgor in mature leaves is maintained by osmotic adjustment. The objective of this study was to determine if young leaves from salt-affected plants were also osmotically adjusted. Pepper plants (Capsicum annuum L. cv. California Wonder) were grown in several levels of solution osmotic potential and various components of the plants' water relations were measured to determine if young, rapidly growing leaves could accumulate solutes rapidly enough to maintain turgor for normal cell enlargement. Psychrometric measurements indicated that osmotic adjustment is similar for both young and mature leaves although osmotic potential is slightly lower for young leaves. Total water potential is also lower for young leaves, particularly at dawn for the saline treatments. The result is reduced turgor under saline conditions at dawn for young but not mature leaves. This reduced turgor at dawn, and presumably low night value, is possibly a cause of reduced growth under saline conditions. No differences in leaf turgor occur at midday. Porometer measurements indicated that young leaves at a given salinity level have a higher stomatal conductance than mature leaves, regardless of the time of day. The result of stomatal closure is a linear reduction of transpiration.     

Chemical and mechanical changes during leaf expansion of four woody species of dry Restinga woodland

Young leaves are preferential targets for herbivores, and plants have developed different strategies to protect them. This study aimed to evaluate different leaf attributes of presumed relevance in protection against herbivory in four woody species (Erythroxylum argentinum, Lithrea brasiliensis, Myrciaria cuspidata, and Myrsine umbellata), growing in a dry restinga woodland in southern Brazil. Evaluation of leaf parameters was made through single-point sampling of leaves (leaf mass per area and leaf contents of nitrogen, carbon, and pigments) at three developmental stages and through time-course sampling of expanding leaves (area and strength). Leaves of M. umbellata showed the highest leaf mass per area (LMA), the largest area, and the longest expansion period. On the other extreme, Myrc. cuspidata had the smallest LMA and leaf size, and the shortest expansion period. Similarly to L. brasiliensis, it displayed red young leaves. None of the species showed delayed-greening, which might be related to the high-irradiance growth conditions. Nitrogen contents reduced with leaf maturity and reached the highest values in the young leaves of E. argentinum and Myrc. cuspidata and the lowest in M. umbellata. Each species seems to present a different set of protective attributes during leaf expansion. Myrciaria cuspidata appears to rely mostly on chemical defences to protect its soft leaves, and anthocyanins might play this role at leaf youth, while M. umbellata seems to invest more on mechanical defences, even at early stages of leaf growth, as well as on a low allocation of nitrogen to the leaves. The other species display intermediate characteristics.     

Leaf age and larval performance of the leaf beetle Paropsis atomaria

ABSTRACT.

• 1 Larval performance of the leaf beetle Paropsis atomaria Oliver was determined for larvae raised on both new and mature leaves of Eucalyptus blakelyi Maiden. Larvae were transferred to mature leaves at different ages; control larvae stayed on new leaves through all instars.
• 2 Only larvae reared on new leaves through the third instar survived to pupate on mature leaves; developmental time was prolonged by 20% and pupal weight was reduced by 50% in these larvae compared with larvae reared entirely on new leaves. Almost all larvae died when transferred to mature leaves as first, second or third instars.
• 3 Low survival and slow development on mature leaves was mainly due to failure by larvae to feed. Larvae palpated leaves and could discriminate among leaf ages immediately, without biting into the leaf tissue.
• 4 New leaves had higher concentrations of oil and tannins than old leaves, while there were no significant differences in nitrogen concentrations in the two types of leaves. Mature leaves were more than 3 times tougher than new leaves, in terms of g mm^?2 of penetrometer force.
• 5 In drought years E. blakelyi may not produce sufficient new leaves to supply specialist herbivores with their preferred food resource. We infer that drought years reduce P. atomaria larval performance significantly, and influence the population dynamics of the insect.

     

Effect of salt stress on antioxidant system of plants as related to nitrogen nutrition

In plants of wheat (Triticum aestivum L.) grown in the media with nitrate (NO ₃ ^? plants), ammonium (NH ₄ ⁺ plants), and without nitrogen (N-deficient plants), the response to oxidative stress induced by the addition of 300 mM NaCl to the nutrient solution was investigated. Three-day-long salinization induced chlorophyll degradation and accumulation of malondialdehyde (MDA) in the leaves. These signs of oxidative stress were clearly expressed in NO ₃ ^? and N-deficient plants and weakly manifested in NH ₄ ⁺ plants. In none of the treatments, salinization induced the accumulation of MDA in the roots. Depending on the conditions of N nutrition, salt stress was accompanied by diverse changes in the activity of antioxidant enzymes in the leaves and roots. Resistance of leaves of NH ₄ ⁺ plants to oxidative stress correlated with a considerable increase in the activities of ascorbate peroxidase and glutathione reductase. Thus, wheat plants grown on the NH ₄ ⁺ -containing medium were more resistant to the development of oxidative stress in the leaves than those supplied with nitrate.     

Leaf age effects of elevated CO2-grown white oak leaves on spring-feeding lepidopterans

Folivorous insect responses to elevated CO₂-grown tree species may be complicated by phytochemical changes as leaves age. For example, young expanding leaves in tree species may be less affected by enriched CO₂-alterations in leaf phytochemistry than older mature leaves due to shorter exposure times to elevated CO₂ atmospheres. This, in turn, could result in different effects on early vs. late instar larvae of herbivorous insects. To address this, seedlings of white oak (Quercus alba L.), grown in open-top chambers under ambient and elevated CO₂, were fed to two important early spring feeding herbivores; gypsy moth (Lymantria dispar L.), and forest tent caterpillar (Malacosoma disstria Hübner). Young, expanding leaves were presented to early instar larvae, and older fully expanded or mature leaves to late instar larvae. Young leaves had significantly lower leaf nitrogen content and significantly higher total nonstructural carbohydrate:nitrogen ratio as plant CO₂ concentration rose, while nonstructural carbohydrates and total carbon-based phenolics were unaffected by plant CO₂ treatment. These phytochemical changes contributed to a significant reduction in the growth rate of early instar gypsy moth larvae, while growth rates of forest tent caterpillar were unaffected. The differences in insect responses were attributed to an increase in the nitrogen utilization efficiency (NUE) of early instar forest tent caterpillar larvae feeding on elevated CO₂-grown leaves, while early instar gypsy moth larval NUE remained unchanged among the treatments. Later instar larvae of both insect species experienced larger reductions in foliage quality on elevated CO₂-grown leaves than earlier instars, as the carbohydrate:nitrogen ratio of leaves substantially increased. Despite this, neither insect species exhibited changes in growth or consumption rates between CO₂ treatments in the later instar. An increase in NUE was apparently responsible for offsetting reduced foliar nitrogen for the late instar larvae of both species.     

Complementary Behaviors of Maternal and Offspring <Emphasis Type="Italic">Spodoptera littoralis</Emphasis>: Oviposition Site Selection and Larval Movement Together Maximize Performance

The selection of oviposition and feeding sites within cotton plants by Spodoptera littoralis was investigated in the field in 2 years, 2007 and 2008. The female moths exhibited significant oviposition preference for young leaves (YL), particularly the 3rd and 4th leaves from top. The larvae originating from egg batches deposited on YL fed mostly in situ for about 5 days, after which they gradually moved their feeding site toward fully expanded or mature leaves on the same individual plant or on neighboring plants. Larvae hatching from batches deposited on fully expanded leaves (FE) fed in situ only for about 2 days, after which they moved toward younger leaves, where they fed for about 3 more days. After the fifth day, however, larvae of the two groups dispersed mainly downward and outward from their hatching site until the end of a 12-day observation. Larvae hatching from eggs deposited on mature or pre-senescent leaves (MP) moved mainly horizontally to other plants after a slight upward shift. The YL and FE larvae grew significantly faster than MP larvae, both in the field and in a laboratory experiment. In the laboratory experiment, the larval period was shorter and the pupal weight was higher when the animals were offered young leaves or young and fully expanded leaves, than when the animals were offered mature and pre-senescent leaves during the first 5 days after hatching. Possible causes and advantages of the exhibited oviposition preference, as well as the apparent ability of larvae to correct for small egg misplacements made by the females, are discussed.