An analysis of the growth of forced tulips. 1. Changes in plant fresh and dry weights during growth at two temperatures

Changes in the fresh and dry weights of the component parts of plants of tulip cv. ‘Apeldoorn’ were followed in bulbs kept at low and high temperatures (9 and 18°C respectively) from the time of completion of flower differentiation until anthesis.There were marked differences between shoot dry weights at the two temperatures. At 9°C the stem, leaves and flower grew exponentially throughout the whole period, but at 18°C the specific growth rate of the stem and leaves declined throughout the period of the experiment. At 9°C the proportion of total dry weight in shoots and daughter bulbs was higher than at 18°C, and the proportion in the mother bulb was correspondingly smaller.At both temperatures the $\text{fresh weight}\text{dry weight}$ ratios of the mother bulb, shoot and daughter bulbs declined during dry storage, the decline being greater at 9°C. After planting, the ratio for all plant parts increased at 9°C, but scarcely changed at 18°C.These results are discussed in relation to dormancy, to the low-temperature requirement for successful and rapid flowering and to flower quality.     

Yield components and fruit development in ‘Golden Delicious’ apples as affected by the timing of nitrogen supply

The nitrogen (N) supply of ‘Golden Delicious’ was changed in various ways during the growing season by altering the N concentration of nutrient solutions or by urea sprays. The terminal shoot growth increased with the duration of “high” N supply, especially with the early summer application where some degree of correlation with the N values of the leaves was established. Blossom density was decreased only at continuously low N supply, when evaluated on the basis of the previous year's crop level. Fruit set was reduced when N in spur leaves, immediately after bloom, dropped below 2.8–3.0%, which occurred with continuously low N, or with high N supply only in the early summer. Growth of fruits at a definite $\text{fruit}\text{leaf}$ ratio increased with N supply and, with some variation between years, the N supply during the early part of the fruit growth period was the more important. The yellow colouring of the fruit at certain $\text{fruit}\text{leaf}$ ratios was greater at low N levels or when the N supply was low during the later part of the fruit growth period. Other effects on fruit quality and composition were small or experimentally inconsistent when the more N-deficient treatments were excluded. The relative importance of the timing of N supply on the different components of yield and fruit quality is discussed.     

Effects of shoot size,number of continuous-light cycles and solar radiation on flower initiation in the carnation

Carnation plants (Dianthus cary ophyllus L.) cultivar ‘White Sim’, were grown in containers in a glasshouse under short (8 h) days. When the primary shoots had 4, 8 or 12 pairs of visible leaves, the plants were moved to a continuous-light area, lit by tungsten lamps for 5, 10, 15 or 30 days, and then returned to short days. This was repeated with several sets of plants at different times of year to obtain a range of radiation flux densities.The number of continuous-light cycles required to initiate a given proportion of shoots was dependent upon the radiation integral, a generalised linear model gave quantitative relationships between the proportion of responding shoots, the number of cycles of continuous light (CL) and the radiation integral. For shoots with 4 visible leaf pairs the model

$\text{keta;=μ+∝X}{}_1\text{+βX}{}_2$

accounted for 83% of the deviance, where η is the linear predictor, μ, α and β are parameters, X₁ = log_e (number of CLs + 1) and X₂ = log_e mean radiation (calories cm^?2 day^?1). For shoots with 8 visible leaf-pairs, 76% of the deviance was removed.Under low radiation integrals, intra-plant competition resulted in only a small proportion of shoots on a plant initiating flowers; increasing the number of CL cycles only partially mitigated this effect. At low radiation integrals, shoots that failed to initiate flowers in CL were often delayed by this treatment and initiated flowers later than shoots in short days. Both the CL-requirement and the limiting effect of the radiation integral on the proportion of shoots that initiated flowers decreased as shoot size increased.It is concluded that competition for photosynthetic assimilates under low radiation conditions can severely limit flower initiation in the carnation.     

Environmental and chemical control of growth and flowering of Chamelaucium uncinatum Schauer

The main factor affecting floral initiation of Geraldton Wax-Flower (Chamelaucium uncinatum) is the photoperiod, while temperature is the major factor affecting flower development. Four weeks of short days (SD) are generally required for obtaining full flowering. The number of flowers produced per plant increases with increasing the number of SD. Under mild temperatures of $\text{20}\text{14°}\text{C}$ (day/night), plants initiated flowers even in long days (LD). However, fewer flowers were produced and on higher nodes as compared to SD plants. Chlormequat promoted flowering under prevailing summer conditions of high temperatures and LD. Under prevailing autumn conditions favourable for flower initiation, LD treatment or weekly sprays with gibberellic acid (GA) reduced the number of flowers per plant. Combined treatment of LD and GA reduced both the flowering percentage and the number of flowers per plant. Discontinuing the LD or the GA treatments caused a resumption of full flower initiation.     

Physiological effects of pruning in rose plants cv. Grand Gala

The effect of pruning in rose plants (cv. Grand Gala) was studied in different types of leaves, focusing on chlorophyll (Chl) a fluorescence, carbohydrates, ammonium content, nitrate reductase (NR) activity and biomass parameters. Results on pruned plants showed a higher maximum efficiency of photosystem II (PSII) of dark-adapted leaves, a higher actual quantum yield and a higher proportion of PSII reaction centres that are open, but a lower non-photochemical quenching, indicating a lower energy dissipation as heat, compared to non-pruned plants. These results related to Chl a fluorescence, indicate that pruned plants have a higher capacity for better promoting the photosynthetic light reaction than non-pruned plants. The increased nitrate reductase activity in pruned compared with non-pruned plants, can result from a higher photosynthetic activity resulting in a lower NH₄⁺ accumulation in leaves. Pruning promoted a large number of metabolic sinks (flower removal) that may cause depletion of stored carbohydrates flowing from lower plant parts (arched shoots) to the new developing flower shoots. However, although in a lower concentration, carbohydrate contents were sufficient to promote the development of new flower shoots since the yield was similar for pruned and non-pruned plants. However, pruned plants showed higher turgor than non-pruned plants.     

The impact of within-row spacing on the productivity of glasshouse roses grown in two planting systems

Summary

Stem yield and quality of roses for cut flower production were evaluated. The plants were grown in two planting systems as an alternative to the traditional ``vase-shaped'' system. In the trellised system, two cultivars of Rosa hybrida (cvs Gabrielle and Kardinal) were planted in a commercial glasshouse in 3.m sections of bed. Within-row spacing was varied to give 6–16 plants m<sup>–2</sup>. After a three-month establishment phase the basal shoots were bent to an angle of 308 above horizontal and restrained with a trellis wire. Flowering shoots sprouting from axillary buds along a basal shoot were harvested at their lowest node, minimizing branching. Compared with ``vase-shaped'' rose plants at the same density, trellised roses produced 24% more basal shoots, 46% more flowering shoots (cv. Gabrielle) and approximately 46% less blind shoots per plant over five months. Phenotypic variation was greater in cv. Gabrielle than in cv. Kardinal in response to within-row spacing, as indicated by the number of basal shoots formed. Within-row spacing, over the range explored, did not affect the number of flowering shoots per basal shoot. Trellising rose plants increased stem yield and quality, but production over the long-term requires further investigation. The single shoot planting system contained a mixed population of single-stemmed rose plants of Rosa hybrida (cvs Gabrielle and Gerdo). It was grown in a field over a range of within-row spacings to give 20–105 plants m^–2. Over three harvests, increasing the number of plants by 10 plants m^–2 reduced the proportion of flowering shoots by 4.4%. Expressed on a unit area basis, a five-fold increase in plants m^–2 produced a three-fold increase in stem production.     

Effects of flat plastic film covering and tunnel protection on the development of early lettuce

The results of trials with lettuce that was given a temporary cover of polythene sheets of 0.05 mm thickness after being planted in the open in March, indicate that the covering should not be removed until the minimum soil temperature at a depth of 10 cm reaches 4°C. This occurred in 1973 after 14 days when planting on March 7th, and after 7 days when planting on March 19th. The results obtained with perforated polythene were better than with unperforated sheeting.It is possible to advance cropping by 1 week at least. A temporary cover always improves the weight of heads and this is attributed to the increased water content of covered plants and to their larger number of heavier — and therefore probably also larger — leaves. The $\text{length}\text{width}$ ratio of leaves was smaller in plants that were given temporary cover than in those that had not been covered.The differences referred to were considered to be mainly due to the more favourable temperatures under the plastic film and therefore also with improved root development in the first stages of the plant's life.     

Manual and chemical induction of side-shoot formation in apple trees in the nursery

An experiment was set up to find a manual method for side-shoot formation as an alternative to the use of chemicals. On growing buds of 2 apple cultivars — budded August 1976 on M.9 rootstock — which often do not form laterals in the nursery (‘Red Boskoop’ and ‘Benoni’), the following treatments were carried out in the summer of 1977: decapitation (removal of the growing-point plus all young leaves); removal of the young leaves, leaving only the actual growing-point intact; spraying with 0.176% FR $\text{570}\text{3}$ (containing 0.15% May and Baker 25 105). All these treatments were applied at about 55 cm shoot length. In a separate series, the young-leaf removal was repeated at about 65–75 cm shoot length. Untreated trees served as controls.All treatments stimulated side-shoot formation; M&B 25 105 most of all. The manual treatments gave similar results with respect to total shoot number but not to height and orientation of the laterals or the vigour gradient along the stem. From the point of view of suitability of the side shoots (i.e. sufficient height above the soil and a large crotch angle), only the chemical treatment and the once-repeated removal of young leaves proved satisfactory. The latter method may offer an alternative to the use of chemical branching-agents.The results are discussed in relation to studies on apical dominance.     

Apical Dominance and Flower Initiation in the Rose

The initiation of leaves and flowers by selected axillary buds of the glasshouse rose cultivar Sonia (syn. Sweet Promise) has been studied both while their extension growth was inhibited by apical dominance and after the inhibition had been removed at one of two times (“early” or “late”). Leaf initiation occurred during growth inhibition so that leaf primordia accumulated in the axillary buds. Flower initiation began, with both treatment times, only after removing apical dominance. Although the total number of leaf primordia formed before the flower was greater in plants of the “late” treatment, the axillary shoots produced in both treatments had similar numbers of leaves with expanded leaflets. Thus many leaf primordia of the “late” treatment plants became scales. The evidence suggests that flower initiation cannot begin while an axillary bud is subject to apical dominance, and that after its removal another factor results in the production of shoots with a relatively constant number of leaves with expanded leaflets.     

Controlling the growth and development of rose plants after planting

The effects of pinching and lateral bud removal (deshooting) on the development of structural shoots, the number of flowers, and the average flower stem length in young rose plants were examined, using the cultivars ‘Baccara’, ‘Sonia’ and ‘Belinda’. The effect of deshooting on flower yield varied with each cultivar. It did not affect the number of ‘Baccara’ flowers, but increased ‘Sonia’ and ‘Belinda’ flower production by 50% and 75%, respectively. Leaving flowers to bloom out on plants before the start of commercial harvest resulted in a decrease in the length of the flower stems and also reduced the beneficial effect of deshooting on flower yield. Deshooting enhanced structural shoot formation (“bottom breaks”). Pinching flower buds of structural shoots increased the number of ‘Baccara’ flowers in comparison with pruning these shoots to 40–60 cm, as in common practice. Deshooting of the structural shoots of ‘Sonia’ and ‘Belinda’ increased the number of flowers in both cultivars.     

Castanea sativa plantlets proliferated from axillary buds cultivated in vitro

Chestnut plants were proliferated in vitro from axillary buds of juvenile shoots. N6-Benzyl-aminopurine (BAP) at 0.1?0.5 mg l^?1 was optimal for shoot multiplication. The important role played by the macronutrient formula on shoot multiplication, and especially on the rooting-stage, is emphasized. The MS ($\text{1}\text{2}$ NO₃) macronutrients gave the best rooting percentage as well as the highest number of roots per rooted shoot. In these experiments, shoots remained in the 3 mg l^?1 indole-3-butyric acid (IBA) medium for 12 days, after which they were transferred to an auxin-free medium where roots developed fully. Optimum rooting was achieved by immersing the 1 cm basal end of shoots in concentrated IBA solutions (0.5?1 mg ml^?1) for periods ranging from 2 to 15 min.     

Influence of temperature on the growth of Solanum nigrum and Amaranthus hybridus

Experiments were conducted in controlled-environment chambers using base-line growth study conditions to evaluate the response of Solanum nigrum and Amaranthus hybridus, two tropical leafy vegetables, to day/night temperatures of temperatures of $\text{25}\text{25}$ and $\text{35}\text{30°}\text{C}$. Both species had superior stem length, leaf area and dry-matter yields at $\text{30}\text{25°}\text{C}$. The cool temperature of $\text{25}\text{20°}\text{C}$ reduced the growth of most plant parts measured, with leaf production being particularly affected in A. hybridus and stem length in S. nigrum. Both species had rapid mean relative growth rates during the 7–14-day growth period. This growth rate was sustained by S. nigrum during the 14–21-day growth period. The nearest to optimum temperature for both species was $\text{30}\text{25°}\text{C}$, based on the production of leaves and stems, which are the nutritionally important plant parts in these species.     

Some effects of varied magnesium nutrition on the growth and composition of olive plants (cultivar ‘chondrolia chalkidikis’)

Olive plants (Olea europaea cultivar ‘Chondrolia Chalkidikis’) were grown in perlite: sand (1 : 1) cultures irrigated with nutrient solutions widely varying in magnesium (Mg) levels. When calcium (Ca) concentration in solution was 4 mM, maximum fresh weight (Fw) was produced with 0.4–2 mM Mg. Above 2 mM Mg in solution, fresh weight yield declined. The ratio of $\text{Ca}\text{Mg}$ in solution for optimum vegetative growth of olive trees was 2.Ca concentration of leaves and roots fell consistently with increasing Mg concentration in solution from 0.005 to 20 mM. When the concentration of Ca was 0.5 mM, an increase of Mg in solution from 3 to 20 mM did not further reduce Ca content of tissue. Mg concentration of leaves and roots increased, but not in proportion to the increase of Mg in the nutrient solution. An increase of Mg in solution from 2 to 10 mM was followed by a proportional increase of manganese (Mn) content of leaves. Above 10 mM Mg, a plateau in Mn concentration was reached.The zinc (Zn) content of leaves and roots was increased when Mg in solution increased up to 0.2 mM, then was reduced in the range 0.2–2 mM Mg and remained constant between 2 and 20 mM Mg. Other elements like copper (Cu) and iron (Fe) were not affected by increasing Mg concentration in solution.     

Inhibition of flowering of Mexican- and Guatemalan-type avocados under tropical conditions

Avocado trees of a range of cultivars growing in Darwin, northern Australia (average yearly maximum 33°C, minimum 23°C), were observed for flower and shoot development. Terminal buds of the cultivars ‘Fuerte’, ‘Rincon’ and ‘Edranol’ sampled in July were not floral. Buds which did not burst were sampled in September and they contained developing flowers with perianth primordia. Vegetative extension growth resulted from laterals proximal to the inhibited terminal buds.Avocado trees of the cultivars ‘Fuerte’ and ‘Hass’ which had initiated floral buds were transferred to controlled environment chambers with 33°C day, 23°C night ($\text{33}\text{23}$) or 25°C day, 15°C night ($\text{25}\text{15}$) with a 12-h photoperiod and photon flux density of 400 μmol m^?2 s^?1 (400–700 nm). At $\text{33}\text{23}$ the trees had fewer flowers and a shorter flowering period than at $\text{25}\text{15}$. Inhibited floral buds and lateral vegetative extension resulted at $\text{33}\text{23}$, as observed in northern Australia. The unburst buds had developing flowers with perianth and stamen primordia.The controlled environment experiments showed that the abnormal flushing behaviour of Mexican- and Guatemalan-type avocados growing in northern Australia was due to high temperature. Floral development was inhibited at the stage of stamen differentiation.     

Adaptation of the tropical hybrid Euphorbia × lomi Rauh to the exposure to the Mediterranean temperature extremes

Poysean (Euphorbia × lomi Rauh) has been introduced in the Mediterranean countries as an ornamental plant for indoor uses. When used outdoor, few information is available about its ability to withstand the Mediterranean temperature extremes. An experiment in an open stand was performed to evaluate poysean tolerance to the winter and summer temperatures of the thermo Mediterranean climate and its ornamental value for urban greening. Two genotypes of poysean (Nguen Muang, NM; and Soi Budsanin, SB) with similar bracts and flower colours were grown at either 2 or 3 plants per pot during 23 months. Number of flower racemes and leaves per plant and plant height were recorded monthly. Overall ornamental value of each pot was scored by means of a panel test (PT) performed by independent examiners. Score assignment was homogeneous between examiners. On average, NM showed a 36% lower number of flower racemes, but a 30% higher ornamental value than SB. During fall and beginning of the winter, NM showed a higher number of flower racemes per plant than SB. Increasing plant density from 2 to 3 plants per pot did not influence flower racemes and leaves per plant. From March to November of the second year, number of flower racemes in NM was similar to the first year, whereas SB flower production was markedly higher, which can be due to a genotypic difference to Mediterranean temperature tolerance. Correlation between number of flower racemes per pot and ornamental value was higher in SB than NM, which suggest that in NM flower abundance contribute less to the pot ornamental value. The present data suggest that poysean is able to withstand the Mediterranean temperature extremes and still produces flower racemes during winter, which indicate it as a suitable ornamental plant in outdoor applications.     

The effect of temperature on growth and dry matter production of lychee seedlings

In lychee (Litchi chinensis Sonn.), high day/night temperatures ($\text{30}\text{25}$, $\text{25}\text{20}$, $\text{20}\text{15}\text{°}\text{C}$ compared to $\text{15}\text{10}\text{°}\text{C}$) increased stem extension, node and leaf production and plant dry weight in seedling selections of 6 cultivars (‘Bengal’, ‘Haak Yip’, ‘Kwai May’, ‘Gee Kee’, ‘Tai So’ and ‘Wai Chee’). The mean daily base temperature for shoot growth (node production) was estimated by linear correlation to be 11.0°C for the seedlings. High temperatures also increased the proportion of leaf and decreased the proportion of root in the total dry weight. There was a strong effect of cultivar on all aspects of growth, but the responses to temperature were similar.This experiment shows that temperatures in many tropical and warm sub-tropical areas where lychees are grown are too high to induce satisfactory vegetative dormancy prior to floral initiation. The assessment of lychee seedlings for low vigour in a heated glasshouse appears to be a useful technique for the initial screening of adapted genotypes (which flower and fruit under warm conditions) prior to field evaluation.     

Relationships among mineral nutrition,ethylene and post-harvest physiology in apples on six rootstocks

The relationships among several mineral elements of August-sampled leaf October-harvested fruit, maturity and post-harvest quality factors of ‘Starkspur Golden Delicious’ apple trees grown on Seedling, Malling (M) 1, Malling Merton (MM) 106, M 7, Oregon Apple Rootstock (OAR 1) or M 26 in a high-density orchard during 1980–1982 were evaluated. Positive correlations were found between leaf N, K and P and fruit N, K and P, respectively, in most rootstocks. Leaf Ca did not correlate with fruit Ca; thus leaf analysis cannot be recommended for estimates of fruit Ca. Both leaf and fruit N positively correlated with fruit green color and negatively with fruit soluble solids in all rootstocks. Fruit Ca and fruit P were both negatively correlated with fruit soluble solids at harvest and after 6 months of 0°C storage for all rootstocks. The ratio of fruit $\text{N}\text{Ca}$ was positively correlated with internal ethylene in MM 106, M 7 and OAR 1, while fruit $\text{K}\text{Ca}$ ratio was positively correlated with titratable acidity in all rootstocks. Fruit Ca showed negative correlations with bitterpit, storage rot and field internal ethylene, but positive correlation with firmness. Yield was positively correlated with leaf and fruit N, Ca and Cu but slightly negatively correlated with B of those tissues. Higher yield was associated with lower leaf K concentrations. Fruit green color was negatively correlated with soluble solids and titratable acidity. Fruit dry matter was highly positively correlated with soluble solids and titratable acidity in MM 106, OAR 1 and M 26. Soluble solids at harvest were strongly predicted by pre-harvest dry matter.     

Carnation yield patterns: The effects of plant density and planting-date

Carnations, cultivar ‘White Sim’, were planted on 17 January, 12 March, 11 July, 12 September and 7 November, at densities of 12.9, 25.8, 51.7 and 103.3 plants m^?2. For each planting-date, yields within a year from planting were asymptotically related to plant density. The mid-winter plantings gave the highest yields and the July planting the lowest.Yield patterns, derived from a weighted moving average, were affected by both the date and the density of planting. At high density, a major part of the year's yield came from the first flush, accounting for 48% of the total yield in the September planting and 75% in the March planting. At the low density, the first flush was only 26–31% of the year's yield. After the first flush, crop yields were suppressed more at higher densities, especially in the November, January and March plantings. Densities of 25.8 and 51.7 plants m^?2 gave the best continuity of production per unit area, whilst the lowest density gave the best continuity of production per plant.The suppression of flower initiation was related to the amount of light; in November less than 20% of the incident light penetrated the canopy of a high-density September planting. Continuous light did not materially increase the number of shoots per plant that initiated flowers, its greatest effect being to produce earlier initiation.     

Temperature influences nutrient absorption and uptake rates of bananas grown in controlled environments

We explored the influence of temperature on the concentration of nutrients in banana plants, the nutrient uptake rate, apparent root transfer coefficient ($\text{}\text{?}$ga) and the relationship between accumulation of dry matter and nutrient. Young banana plants (Musa (AAA group, Cavendish sub-group) ‘Williams’) were grown at six temperature regimes (17/10–37/30°C) in sunlit growth chambers for 12 weeks.The amount of nutrient absorbed was influenced by the amount of growth made, but the link between the two differed from one element to another. Temperatures less than $\text{29}\text{22°}\text{C}$ reduced the concentration of all elements in the whole plant, except Fe.Temperature influenced the root uptake rate of B 10-fold; K, Na, Ca, Fe and Zn 3–4-fold; and N, P, Mg, Mn, Cu, Cl 1–2-fold. Among the elements the highest recorded rate was 12 mg g^?1 day^?1 for K at $\text{33}\text{26°}\text{C}$. The optimum temperature for nutrient uptake rates differed among the elements. This was accounted for largely by greater growth at those temperatures of organs with high concentration of particular elements.The $\text{}\text{?}$ga (an estimate of efficiency of uptake) of B varied 12-fold among treatments; K, Ca, Mg, Na, Mn, Zn and Cl varied 3–5- fold and N, P, Cu and Fe varied 2–3-fold.The ratio of relative nutrient accumulation rate, R_m, to the relative growth rate, R_w, was most stable across temperatures for N and least stable for B and Na. However, the trend was for $\text{R}{}_{\mathrm{<mtext>m</mtext>}}\text{R}{}_{\mathrm{<mtext>w</mtext>}}$ to increase as temperature rose, indicating an absorption of nutrients greater than might be expected from a change in growth rate as temperature increased, and a decreased efficiency in their utilization for plant growth.