Differences In Leaf Number Research Articles

Cold Atmospheric Plasma (CAP) Treatment of In Vitro Cultivated Plum Plantlets—A Possible Way to Improve Growth and Inactivate Plum Pox Virus (PPV)

Plasma technology, relatively new in the fields of biomedicine, agriculture, and ecology, is the subject of intensive research as a prospective means of decontamination of various microorganisms (bacteria, viruses, and fungi). The objectives of the present study were to follow the effect of cold atmospheric plasma (CAP) treatment on in vitro grown plum plants (Prunus domestica L. ‘Kyustendilska sinya’ cv.) and the possibility of eradicating or inactivating plum pox virus (PPV) causing Sharka disease by CAP. The source tree is naturally co-infected by PPV (both M and D strains). In the experiments, two different plasma sources were used. First, a surface-wave-sustained Argon plasma torch and second, an underwater diaphragm discharge. For the treatments, nodal segments (10 mm in length) from in vitro cultured plum plants with or without one leaf were prepared. Apical shoots from treated plants (PPV-positive and negative clones as well non-treated controls) were cultivated in vitro for four passages. Then they were rooted and acclimatized to ex vitro conditions, and their virus status was observed periodically for more than 3 years after treatment for the appearance of Sharka symptoms. All plants, acclimatized to ex vitro conditions, were tested for PPV by immune capture–reverse transcription–polymerase chain reaction (IC-RT-PCR). As a first step in understanding the plasma treatment of living plants, a plasma treatment variant causing no damage must be established; this has been done in our previous works. Treatment of plants by plasma with parameters that have been carefully selected leads to better development than the non-treated plants. In the treated in vitro plants, no significant differences were found in the number and length of shoots compared to the control plantlets. In ex vitro acclimated plants, greater stem length was reported, but no differences in leaf number were observed. No significant differences in growth were recorded between the control and plants that were treated twice or three times. At this stage, 3 years after ex vitro cultivation in a greenhouse, Sharka symptoms were not registered on treated in vitro negative PPV plants, and the virus was not detected by IC-RT-PCR. Very mild symptoms were showing in CAP-treated PPV-positive plants. Development of typical Sharka symptoms on non-treated controls were observed.

Nitrogen application and differences in leaf number retained after topping affect the tobacco (Nicotiana tabacum) transcriptome and metabolome

BackgroundAgronomic treatments such as the application of nitrogen fertilizer and topping (removal of the inflorescence and top leaves) cause substantial changes in plant metabolism. To explore these changes, we conducted comparative transcriptomic and metabolomic analyses of leaves collected from four positions along the stem on plants exposed to two nitrogen doses and with different numbers of leaves retained after topping in tobacco (Nicotiana tabacum).ResultsWe identified 13,330 unique differentially expressed genes and 32 differentially abundant metabolites. Through RNA-seq and WGCNA analyze, we constructed 2 co-expression networks (green and blue) highly correlation to N application and leaf number retained, predicted a hub gene NtGER3 may play an important role in N metabolism related to amino acid (cysteine) through CK pathway in tobacco leaves, NtARFs may participated in modulating the auxin signal and N in bottom leaves and NtRAP2.12 as key gene involved in N regulation by ethylene pathway. What’s more, our data prove C/N transformation and balance affect the “source – flow - sink” redistribution and remobilization in tobacco during growth and development process.ConclusionsOverall, this comparative transcriptomics study provides novel insight into the complex molecular mechanisms underlying plant responses to different levels of nitrogen application and the number of leaves remaining after topping in plants.

NPK Fertilizers for Elephant Foot Yam (Amorphophallus paeoniifolius (Dennst.) Nicolson) Intercropped with Coffee Trees

<p>ABSTRACT</p><p>Fertilizer application in elephant foot yams (Amorphophallus paeoniifolius (Dennst.) Nicolson) intercropping system is rare in Indonesia, therefore, NPK fertilizers experiment was conducted under the shade of 10-year-old coffee plantation at Leuwikopo Experimental Farm, Bogor, Indonesia, in order to increase the productivity of elephant foot yam intercropped with coffee trees. Prior to planting, 20 ton ha-1 of goat manure was applied. Four NPK combinations, i.e., N, P2O5, K2O at the rate of 0, 0 and 0; 100, 60 and 80; 125, 60 and 100; and 150, 60 and 120 kg ha-1, were applied. Results showed that there were no significant differences in leaf number per plant, petiole size and rachis length among treatments. Application of NPK decreased photosynthetic rates, while increasing rate of N and K2O had no effect on photosynthetic rates. NPK application at the 100 N, 60 P2O5 and 80 K2O kg ha-1 (N100P60K80 treatment) or larger prolonged growth duration regardless of NPK levels, and there was a close relationship between corm yield and growth duration. As a result, corm fresh mass was higher in the 100:60:80 kg ha-1 treatment than in control. In the N125P60K100 and N150P60K120 kg ha-1 treatments, leaves were damaged by heavy rains and winds, counteracting beneficial effect of NPK on growth duration and corm yield. These results suggested the importance of delay of entering dormancy for an increase in productivity of A. paeoniifolius.</p><p>Keywords: NPK fertilizers, photosynthesis, productivity, prolong growth, tuber crop</p>

Effect of different temperature regimes on morphological and flowering characteristics in gladiolus (Gladiolus (Tourn) L.)

Effect of different growth temperature regimes was studied on morphological and flowering characters of two gladiolus cultivars viz. Snow Princess and American Beauty. Both the cultivars were raised in Phytotron using corm size of 3.5–4.0 cm in diameter. Temperatures treatments were maintained 20/18, 26/22 or 30/26 °C (Day/Night) with 14 h light and 60–65 % relative humidity in the growth chambers. Days required for corm sprouting decreased as the temperature levels increased. 30/26 °C temperature was found with lowest days for corm sprouting. Sprouting percentage of corms was 100 % under all the treatments in both the cultivars. There was non-significant difference in leaf number and number of florets per spike under all the temperature. Number of florets was maximum at 20/18 and 26/22 °C temperatures and was nil at 30/26 °C. The taller spike and rachis length was found under treatment T2 (26/22 °C) in cultivar American Beauty. The duration of flowering reduced with the temperature increase. Maximum duration of flowering on spike (5.67 day) was found in control treatment (20/18 °C). With few exceptions, adverse effect of increase in temperature was substantial. However, the effect of highest temperature of 30/26 °C was more adverse and significant for various vegetative and reproductive growth parameters in both the cultivars. Increase in temperature concomitantly decreased flower initiation, hastened sprouting of corms and increased plant height.

Biomass accumulation and partitioning, photosynthesis, and photosynthetic induction in field-grown maize (Zea mays L.) under low- and high-nitrogen conditions

The objectives of this comparative study were to investigate the responses of biomass accumulation and partitioning to nitrogen supply and to examine the effect of low-nitrogen supply on the photosynthetic responses of maize leaves to steady-state and dynamic light. While the difference in leaf number and stem diameter was not statistically significant, there was a significant difference in plant height between the low-nitrogen and high-nitrogen maize plants. During grain-filling period, the ear leaf of the low-nitrogen maize plants possessed lower values of maximum photosynthetic rate, maximum stomatal conductance, maximum transpiration rate, apparent quantum yield, light compensate point, and carboxylation efficiency than did that of the high-nitrogen maize plants. Contrarily, lower values of intercellular CO2 concentration and dark respiration rate were observed in the high-nitrogen maize plants. In addition, a slower response to simulated sunflecks was found in the ear leaf of the low-nitrogen maize plants; however, stomatal limitations did not operate in the ear leaf of the high-nitrogen or low-nitrogen maize plants during the photosynthetic induction. As compared to the high-nitrogen maize plants, the low-nitrogen maize plants accumulated much less plant biomass but allocated a greater proportion of biomass to belowground parts. In conclusion, our results suggested that steady-state photosynthetic capacity is restricted by both biochemical and stomatal limitation and the photosynthetic induction is constrained by biochemical limitation alone in low-nitrogen maize plants, and that maize crops respond to low-nitrogen supply in a manner by which more biomass was allocated preferentially to root tissues.

Seedlings of temperate rainforest conifer and angiosperm trees differ in leaf area display.

The contemporary relegation of conifers mainly to cold or infertile sites has been ascribed to low competitive ability, as a result of the hydraulic inefficiency of tracheids and their seedlings' initial dependence on small foliage areas. Here it is hypothesized that, in temperate rainforests, the larger leaves of angiosperms also reduce self-shading and thus enable display of larger effective foliage areas than the numerous small leaves of conifers. This hypothesis was tested using 3-D modelling of plant architecture and structural equation modelling to compare self-shading and light interception potential of seedlings of six conifers and 12 angiosperm trees from temperate rainforests. The ratio of displayed leaf area to plant mass (LAR(d)) was used to indicate plant light interception potential: LAR(d) is the product of specific leaf area, leaf mass fraction, self-shading and leaf angle. Angiosperm seedlings self-shaded less than conifers, mainly because of differences in leaf number (more than leaf size), and on average their LAR(d) was about twice that of conifers. Although specific leaf area was the most pervasive influence on LAR(d), differences in self-shading also significantly influenced LAR(d) of large seedlings. The ability to deploy foliage in relatively few, large leaves is advantageous in minimizing self-shading and enhancing seedling light interception potential per unit of plant biomass. This study adds significantly to evidence that vegetative traits may be at least as important as reproductive innovations in explaining the success of angiosperms in productive environments where vegetation is structured by light competition.

Plant Growth Is Stimulated by Tea-seed Extract: A New Natural Growth Regulator?

Various plant extracts are being marketed claiming to enhance both crop yield and quality and being environmentally friendly. However, these claims are rarely documented by scientific data. In this study, we investigate the growth regulatory effect of Tea Seed Powder (TSP), a saponin-rich waste product from tea seed (Camellia sp.) oil production. The product was tested in various concentrations on Lemna growth and as a soil and spray application on growth of pot grown beet, mustard, oat, and barley. Finally, two treatments, 0.2 g TSP/L dry soil and weekly sprays with TSP solutions corresponding to 1.5 g TSP/m2, were tested for effects on strawberry yield. The results showed significant growth-enhancing effects on the sterile Lemna of ≈20% above control, demonstrating that the growth increase was a plant physiological response to TSP rather than an indirect effect of TSP affecting pests and diseases or improving nutrient uptake. Soil-treated, pot-grown beet, oat, and barley plants showed significant biomass increases in the range of 27% to 41% above control at concentrations of ≈0.3 g TSP/L dry soil, whereas increases of 14% to 26% were observed in plants sprayed with 0.15 to 1.5 g TSP/m2. Sprayed strawberries had a 38% higher berry yield compared with control plants in 2008, whereas no difference in leaf number and area, number of runners, and inflorescences were detected. In 2009, there were no significant observable differences between sprayed plants and controls. Soil-treated strawberry plants, however, showed a decrease in leaf number in 2008 and in strawberry yield in 2009. The study concludes that TSP has pronounced and direct physiological effects on plants, which can both increase and decrease growth and yield depending on the applied dose. The growth-enhancing effect could be used commercially to improve crop yield; however, because TSP is also known to be very harmful to earthworms, possible environmental effects of the use of TSP in agriculture and horticulture must be considered before use.

Growth and fitness of triazine‐susceptible and triazine‐resistant common waterhemp (Amaranthus tuberculatus var. rudis)

Two greenhouse trials were conducted over a 2 year period (2004 and 2005) to compare the relative growth potential and fitness of triazine‐susceptible (TS) and triazine‐resistant (TR) waterhemp biotypes. Waterhemp plants from each biotype were grown in 6 L pots in the greenhouse in a completely randomized design. There was no difference in leaf number, plant height, plant biomass, time to bud or time to flower between the two biotypes. The TR female waterhemp plants produced 30% less reproductive biomass and 39% less seed than the TS biotype. The fitness penalty associated with triazine resistance was related to reproductive capability, not to vegetative growth.

Growth and development of Lilium longiflorum ‘Nellie White’ during bulb production under controlled environments

Abstract One-year-old scale and stem bulblets of Lilium longiflorum Thunb. ‘Nellie White’ (Easter lily) were grown under constant and variable growth chamber conditions and greenhouse conditions to compare growth and development and bulb production. Eight temperatures regimes were established using the following: six growth chambers set to provide day/night temperature regimes of 30/26, 26/22, 22/18, 18/14, 14/10 and 10/6 °C; a seventh growth chamber (VAR) programmed to begin at 22/18 °C, then decline in three 4–5 week steps to 10/6 °C, and subsequently increase in three 4–5 week steps to 22/18 °C to simulate seasonal field temperatures in the coastal bulb production area of northern California and southern Oregon; and a double layer polyethylene greenhouse (GH) set to begin cooling at 22 °C and heating at 18 °C. Ten percent of the scale bulblets and 35% of the stem bulblets failed to develop shoots (“no-shows”). “No-shows” increased with increasing temperature with a significant number starting at 18/14 °C. The moderately high GH temperature also induced “no-shows”. Maximum basal bulb (the main planted bulb) weight occurred at 26/22 °C for both bulblet types. Scale bulblets not only produced heavier basal bulbs with a larger circumference than stem bulblets, but also produced heavier stem bulbs. Stem bulb formation and production was maximized in the range of 18/14–26/22 °C and in the GH for scale bulblets. Stem bulb production from stem bulblets did not differ from zero. Scale bulblets produced more basal and stem roots than the stem bulblets at the end of the early growth period, but there was no significant difference at the end of the study. Root fresh weight was greatest in the range of 14/10–18/14 °C and declined at higher or lower temperatures. The VAR and GH treatments had similar root weights to those at 18/14 °C. Shoot length was maximized at 22/18 °C for stem bulblets and in the GH and at 22/18 °C for scale bulblets. Stem plus leaf (shoot) fresh weight was not statistically different between bulblet types with the exception of an increased weight for stem bulblets grown at 22/18 °C. Scale bulblets in the GH had greater stem plus leaf weights than scale bulblets in the other temperature regimes. Shoot leaf number was highest in stem bulblets at 22/18 °C and in the GH. In these two temperature treatments, more leaves were produced by stem bulblets than scale bulblets. In all other treatments, there was no significant difference in leaf number. Bulblet type had no effect on number of flowers produced. Flower number was maximum in the range 10/6–22/18 °C, decreased at 26/22 °C and in the GH, and was absent at 30/26 °C. For bulb production, reduced flowering is desired since flowers are generally removed during the outdoor bulb production period. Meristem abortion, which also causes a desirable reduction in flowers, was greater in scale bulblets. It occurred at 26/22 °C and was greater at 30/26 °C. Scale bulbs produced the largest main bulbs, with a maximum yield at 26/22 °C.

Influence of Autoclaved Fungal Materials on Spearmint (Mentha spicata L.) Growth, Morphogenesis, and Secondary Metabolism

The influence of autoclaved fungal materials such as culture filtrate, freeze-dried mycelium (FDM), mycelium suspension, and spore suspension (SS) on the growth, morphogenesis, and carvone production of spearmint (Mentha spicata L.) plants was studied. Fungal materials were either applied as a drench or spray on the plants. Spearmint plants (cv. "294099") drenched with SS (1 x 10(8) spores/ml) of Trichoderma reesei showed no significant differences in leaf numbers, root numbers, or shoot numbers compared with nontreated controls. However, significantly higher fresh weights and carvone levels were observed in plants drenched with T. reesei SS compared with the untreated controls. Fungal materials derived from Aspergillus sp., Fusarium graminearum, F. sporotrichoides, Penicillium sp., P. acculeatum, Rhizopus oryzae, and T. reesei were sprayed on spearmint foliage. F. graminearum, F. sporotrichoides, or R. oryzae elicited no enhanced growth, morphogenesis, or secondary metabolism responses. The best growth and morphogenesis responses were obtained employing Aspergillus sp., Penicillium sp., or T. reesei foliar sprays. For example, spearmint cv. "557807" plants sprayed with 100 mg/l FDM T. reesei isolate NRRL 11460 C30 stimulated higher fresh weights (75%), shoot numbers (39%), leaf numbers (57%), and root numbers (108%) compared with untreated plants. This effect was not dose-dependent because similar growth and morphogenesis responses were obtained by testing 10, 100, or 1000 mg/l FDM concentrations. Carvone levels in fungal-treated foliar-sprayed plants were comparable to nontreated controls. However, total carvone levels per plant were higher in fungal-treated plants because of their increased fresh weight.

Variability in abundance and morphological attributes of Zostera marina L. from the southern coast of Korea

The biomass and morphometric features of subtidal eelgrass (Zostera marina) beds were examined in Kwangyang Bay on the south coast of Korea. Benthic samples were collected from four sites at 2-month intervals, and various environmental parameters were simultaneously monitored. Shoot density increased from 15.7±1.4 (mean±SE) in November 1998 to 65.0±6.0 m-2 in May 1999 and gradually decreased during July–September 1999. Total biomass (shoot and rhizome-root) ranged from 20.2±5.5 in September 1999 to 188.5±19.1 g dry weight m-2 in May 1999. Shoot biomass and density were positively correlated, showing a spring peak on an annual cycle. Significant differences in leaf number per shoot, shoot length, third youngest leaf length, leaf width, leaf surface area index, internode length, root length and root number per node were observed among the sampling times. Shoot length and third youngest leaf length were positively correlated with leaf width, but poorly correlated with the leaf number per shoot. Seasonality of eelgrass beds and morphological traits of Zostera marina at Kwangyang Bay were compared to those in other temperate regions of the northern hemisphere.

Characterization of a type II chlorophyll a/b-binding protein gene (Lhcb2*Pp1) in peach. II. mRNA abundance in developing leaves exposed to sun or shade.

Leaf development of shoots exposed to full sunlight and shoots shaded by the canopy was followed in field-grown, mature peach trees (Prunus persica (L.) Batsch, cv. Loring) during the first half of the 1995 growing season. The architecture and size of shaded shoots and sun-exposed shoots differed significantly. Total number of leaves produced on shaded shoots was significantly less than on sun-exposed shoots throughout the season, and differences in leaf number between light conditions increased as the season progressed. The overall patterns of leaf development along sun-exposed and shaded shoots were qualitatively similar. The expression pattern of the type II chlorophyll a/b-binding protein gene, Lhcb2*Pp1, determined by RNA abundance in leaves at different positions along the shoot, was also similar between the two light conditions. The major difference between sun-exposed and shaded leaves was a lower abundance of Lhcb2*Pp1 RNA in mature, shaded leaves compared with sun-exposed leaves. Although the number of fruit per shoot was significantly lower on shaded shoots than on sun-exposed shoots, the rate of fruit drop was not substantially different during the growing season, indicating that quantitative differences in leaf initiation and growth caused by differences in light exposure did not adversely affect fruit retention. However, based on comparison with a previous study of leaf development in non-fruiting trees, reproductive development slowed the rate of vegetative growth without affecting the overall pattern of leaf development along the shoots.

Desempenho de três cultivares de almeirão sob cultivo protegido

O almeirão (Cichorium intybus L.) é uma Asteraceae muito semelhante à chicória da qual se diferencia por possuir folhas mais alongadas, mais estreitas, recobertas por pelos e com sabor amargo mais pronunciado. Avaliou-se o desempenho das cultivares Folha Larga, Pão-de-Açúcar e Catalonha, em estufa com cobertura plástica, em experimento, de julho a setembro/2001, no Núcleo Experimental de Campinas do IAC. O experimento foi disposto em blocos ao acaso, com parcelas subdivididas para época de avaliação, tendo três repetições. Aos 50; 57; 64 e 71 dias após a semeadura foram avaliadas dez plantas de cada subparcela quanto à altura, número médio de folhas, biomassas de matéria fresca e seca e área foliar. Nessas oportunidades foram também avaliadas as produções de folhas em um metro linear de canteiro. Não houve diferença entre as cultivares quanto ao número médio de folhas por planta porém houve interação entre cultivares e época de avaliação para área foliar, biomassas fresca e seca e produção de folhas. A cultivar Catalonha foi a que apresentou maior altura e maior produtividade, embora as biomassas de matéria fresca e seca tenham sido superiores na Pão-de-Açúcar que também apresentou maior área foliar. Recomenda-se, com base na área foliar, a colheita dessas hortaliças até os 64 dias. Concluiu-se que foi viável a produção de almeirão sob cultivo protegido constituindo-se em mais uma alternativa para esse sistema de produção.

Effect of temperature on development and growth potential of axillary buds in roses

The effect of temperature during axillary bud formation on axillary bud development and subsequent shoot growth was investigated. Growth potential of the axillary buds was studied either in situ, by pruning the parent shoot above the bud, or in isolation, by grafting the bud or by culturing the bud in vitro. Although rate of leaf initiation increased with increasing temperature, the number of leaves and leaf primordia in the bud at the time of release from inhibition decreased slightly with increasing temperature. Time until bud break decreased with increasing temperature, as did the total growth period until harvest. The total number of leaves preceding the flower decreased with increasing temperature, while no difference in leaf number was found between shoots grown from buds in situ and shoots from buds in isolation. Shoot size at harvest (sepals reflexing) decreased slightly with increasing pre-treatment temperature, but effects were larger for isolated buds than for buds attached to the parent shoot. The pith to shoot diameter ratio was not affected by temperature and the number of pith cells in cross section decreased only slightly with increasing temperature.

Effects of Fertilizers, Salinity, and Medium on Growth of Phalaenopsis Orchid

Seedling Phalaenopsis (P. Taisuco Eagle × P. Taisuco Rose) plants with an 8- to 10-cm leaf span were grown in 10-cm pots filled with a medium consisting of 70% fine fir bark and 30% peatmoss (by volume). Plants were given (in N–P2O5–K2O) 10–30–20, 15–10–30, 15–20–25, 20–5–19, 20–10–20, or 20–20–20 fertilizers at the 100 or 200 mg N/liter rate. Pots were leached with water following every two fertigations. After 7 months, leaf span, leaf size, total leaf area, and fresh weight were not affected by fertilizer type. The differences in leaf numbers were small. The higher rate of fertilizer resulted in plants with wider leaf span (32.8 vs. 28.5 cm), more (5.5 vs. 4.8), larger (103 vs. 89 cm2) leaves, and greater total leaf area (355 vs. 275 cm2) than did the lower rate. In another experiment, similar plants with a leaf span of 15 to 18 cm were grown in 10-cm pots with 100% fine fir bark or a mixture of 80% fine fir bark and 20% peatmoss. They were fertigated with water having an EC - 0.05, 0.40, 0.75, 1.10, or 1.40 dS·m–1 containing 1 g·liter–1 20–20–20 fertilizer three times and then drenched with their respective water containing 0.6 g·liter–1 Ca NO3)2·4H2O. After 11 months, water salinity did not affect the date of spiking. Plants receiving water with EC = 1.10 dS·m–1 had more leaves and spikes than other treatments. Plants in the bark/peatmoss mix began spiking earlier, had more leaves (6.7 vs. 5.7), and more inflorescences (1.9 vs. 1.5) than those in 100% bark. There was no salinity x medium interaction in all the parameters recorded.

Reduced Oviposition by Green Lacewings (Neuroptera: Chrysopidae) on Cotton Intercropped with Corn, Beans, or Weeds in Nicaragua

In an experiment in small plots planted in Nicaragua, counts of green lacewing (Neuroptera: Chrysopidae) eggs were made on cotton intercropped with corn, beans, or weeds, and in cotton monocultures. Significantly fewer eggs were found on cotton plants intercropped with corn and weeds than in cotton monocultures, but cotton plants tended to be smaller in intercrops. The lower chrysopid egg numbers in cotton intercropped with corn or weeds were significant when adjusted for differences in leaf number per cotton plant and mean cotton leaf area, but not significantly lower on cotton intercropped with beans. Mechanisms are suggested to explain the reduction in egg numbers in the intercrops, including a decrease in the numbers of prey (aphids) and the presence of other predators (earwigs).

Temperature Effects on Growth and Leaf Production in Three Weed Species

Sicklepod (Cassia obtusifoliaL. ♯6CASOB), hemp sesbania [Sesbania exaltata(Raf.) Cory ♯ SEBEX], and showy crotalaria (Crotalaria spectabilisRoth. ♯ CVTSP) were grown in controlled-environment greenhouses with day/night temperatures of 23/17, 26/20, 29/23, and 32/26 C. Plant height, leaf area, and total dry weight at 53 days after planting increased significantly with temperatures between 23/17 and 29/23 C in sicklepod and showy crotalaria, and between 23/17 and 32/26 C in hemp sesbania. In all species, leaves were produced more rapidly as temperature increased. Axillary branch leaf production was greatest at 29/23 C in sicklepod, and at 29/23 and 26/20 C in showy crotalaria; hemp sesbania showed little axillary branch development. Total dry-matter production in all species was closely correlated with leaf area duration, but not with net assimilation rate. Differences in total main stem leaf area in all species were primarily due to differences in leaf number rather than to differences in leaf size at maturity.

Corn Growth Response to Temperature and Photoperiod. III. Leaf Number1

AbstractThe number of leaves formed on a determinate plant species such as corn (Zea mays L.) is dependent on the time between sowing and tassel initiation and on the rate of leaf production at the apical meristem. Both of these processes, and consequently leaf number, are influenced by environmental variables such as temperature and photoperiod. In a controlled‐environment study of two corn hybrids, grown over a wide range of temperature regimes from 16/6 to 38/33°C day/night, a nonlinear leaf number/temperature response was observed. Leaf number was lowest near 18/18° C and highest in the 16/6 and in the 38/33°C conditions. Because of this nonlinearity, leaf numbers observed under differential day/night temperature regimes were sometimes quite different from those observed under constant day/night temperatures but with identical mean temperatures. A leaf number/temperature response function was estimated for each of the hybrids which could be used to predict leaf number for various temperature regimes with 12‐h photoperiods. The response function was found to be in agreement with results in the literature. Differences in leaf number between the two cultivars were consistent with their maturity ranking. Leaf number increased as photoperiod increased; an average increase of 0.71 leaves per additional hour of photoperiod was found. This increase obtained under high light conditions is greater than that recorded previously for other temperate cultivars grown under long day conditions provided by low intensity day‐length extensions from incandescent lighting. Photoperiod sensitivity was not altered by temperature. The number of unexpanded leaves present at tassel initiation was almost constant under different temperature treatments despite changes in total leaf number. In contrast, this number increased when photoperiod was increased. The main ear node position altered with changes in total leaf number but was almost constant relative to the number of mature leaves present at tassel initiation under all temperature and photoperiod treatments.

RESOURCE ALLOCATION ON DWARF SHOOTS OF BIRCH (BETULA PENDULA): REPRODUCTION AND LEAF GROWTH

SUMMARYA hypothesis that the female catkin and leaves on the same dwarf shoot of birch compete for the same limited resources of the bud during their development has been tested with Betula pendula. In all trees studied the mean length of leaves, both in May and July, was 15 to 20% lower on reproductive dwarf shoots with a female catkin than on non‐reproductive dwarf shoots of the same tree. However, there were no significant differences in leaf number or in bud development. The idea of plants as metapopulations and the cost of reproduction in trees are discussed.

Growth of Lettuce Under Controlled Humidity Levels1

Abstract The influence of atmospheric moisture levels of 85% and 50% relative humidity (RH) (3.5 and 11.6 mb saturation vapor deficit respectively) at 20°C for 16:8 long day (LD) cycle on butterhead lettuce, (Lactuca sativa L. cv. Meikoningen), during a growth period of 4 weeks from seeding, was studied in organic soil and liquid cultures. Significantly faster growth rates were evident on plants developing under 85% RH than under 50% in both soil and liquid culture with the largest increases occurring with plants grown in soil culture. The higher humidity level increased leaf number 15%, leaf size 30%, dry weights 62%, and leaf water contents from 93% to 94%. The differences in leaf number and dry weight equalled about 2 days growth difference at 4 weeks after seeding. The density of stomata was greater on plants grown under 50% RH but the total number of stomata per leaf under the 2 humidity levels was the same. The leaf resistance was significantly higher on plants grown under 50% than under 85% RH. The principle significance of high humidity level during growth of lettuce is the production of larger marketable heads with a higher water content in a slighly reduced period of time.