Shoot Extension Research Articles

Early apple fruit development under photoselective nets

The objective of this 2-year study (2017, 2019) was to evaluate the influence of photoselective nets on apple fruit growth, focusing on the initial fruit growth stages of “Pink Lady”. Trees were subjected to four photoselective nets (Blue, Red, White and Yellow) and a standard black one (serving as Control), resulting in 5 light environments (LE), all shading at 20%. From 20 to 90 DAFB, 32 fruit and extension shoots, for each LE, were measured for a total of 11 times during the season. For each LE, fruit gauges were also installed to monitor fruit daily growth parameters, from 50 to 90 DAFB. At harvest, all fruit from each light environment were weighed and quality parameters were measured on 40 fruit per treatment. For each year, correlations were made to test the influence of LEs on final fruit weight and quality, and the impact that extension shoot growth had on fruit growth. In both years, white and control nets led to the production of fruits with higher weight compared to the other treatments (blue, red and yellow nets). In 2019, LEs did not appear to influence the relationship between shoot and fruit growth, probably due to the higher crop load and the massive pruning carried out the previous year. The higher vegetative outburst in this year might have unbalanced resources towards the shoots, than towards the fruit. Results show how weather and orchard management heavily influenced the trees responses. Yet, the consistent findings of final fruit weight, for both years, indicate that different wavelengths influence fruit and shoot behavior, even at early phenological stages. Hence, growers searching for bigger fruit should refer to white and black nets. Further studies approaching this technology can help improve apple production management and knowledge of the use of photoselective nets.

Cryptochrome 1a of tomato modulates nutritional deficiency responses

The blue light photoreceptor cryptochromes are involved in nutritional response pathways in plants. Evidence shows that cryptochromes mediate the control of genes related to nutrients accumulation in plants. However, nothing is known about the role of cryptochrome 1a (cry1a) in tomato (Solanum lycopersicum L.) nutritional stress responses. Thus, this study aims to evaluate the importance of cry1a photoreceptors in plant responses to nutrient deficiency. To this end, we proposed the use of a tomato mutant carrying a lesion in a gene encoding the blue light photoreceptor cry1a (cry1a) and its wild type (WT; cv. Moneymaker). Both genotypes (20-day-old plants) were grown under treatments consisting of a complete nutrient solution and the individual omission of each nutrient (–N, –P, –K, –Ca, or –S) from a balanced nutrient solution. Subsequently, we measured the growth, pigmentation, oxidative stress, and nutrient accumulation, as well as uptake efficiency, transport efficiency, and use efficiency of nutrients in all treated plants. The cry1a plants had greater shoot extension growth than WT plants in all tested growth conditions, although the shoot biomass accumulation with cry1a was greater than in the WT only under Ca omission. Except in the –N and –Ca conditions, the cry1a plants accumulated less root biomass than WT plants. In addition, leaf pigments (chlorophyll a+b and carotenoids) were reduced in the mutant plants compared to WT plants grown under CS, –P, and –S conditions. Thus, considering that WT plants have the full functions of cry1a photoreceptor, here we showed that cry1a plays an important role in the nutrient deficiency responses in tomato, particularly, mediating growth and development of stressed plants through changes in plant growth and oxidative stress, as well as the nutrient contents and efficiencies of transport use.

Variations in growth and architecture in the range limit of Salix humboldtiana, the willow native to South America

The conditions faced by edge populations of a tree species may affect the architecture of individual trees. The latitudinally broad range of Salix humboldtiana Willd. encompasses tropical to cold-temperate climatic regions, with its southernmost population in central Patagonia. We expected S. humboldtiana trees from the southern-edge population to develop smaller shoots and a lower level of axis differentiation than trees of this species from a more northern population, and we expected edge trees to outperform non-edge trees when growing in a common garden at an intermediate latitude. For juvenile individuals of S. humboldtiana from edge and non-edge natural populations, the trunk diameter, height, branching angle, as well as the length, number of nodes, diameter, leaf area, and specific leaf area of the main branch and the trunk annual shoots were measured. The size and extension rates of shoots developed by trees of both origins in a common garden were also evaluated. In natural populations, the shoot leaf area and the specific leaf area were higher for the edge population than for the non-edge population. In a common garden, the shoot extension period and the length were higher for non-edge plants than for edge plants. The growth-period differences between populations in a common garden may support the hypothesis of stress adaptation in the southernmost S. humboldtiana trees.

Establishment of procedure to evaluate soybean for various temperature regimes at seedling stage

Soybean is a legume crop and it has importance for both of its products, bean and oil. The bean of soybean contains many sorts of minerals and vitamins, while Soy oil contains various dietary minerals and used for various raw use and cooking purposes. But the major constraints of soybean production are linked with its germination and emergence which is mainly affected by soil moisture and temperature conditions. To identify the optimum temperature of soybean plant germination and adaptive variety for Pakistani regions, a seedling stage experiment was conducted in the chickpea laboratory of University of Agriculture Faisalabad, Pakistan. Basic purpose of this experiment was to establish the procedure for soybean cultivation to gain profitable yield and it was carried to focus on growth and development in both shoot and roots of the plant sown in specific temperature. Controlled uniform conditions of two different temperature treatments i.e., 25°C and 30°C were maintained and four local genotypes (NARC, Faisal, Ajmeri and Rawal-1) were used. These genotypes showed improved extensive shoot morphology of the plant, while the root morphology remained unaffected.

An In Vitro–Ex Vitro Micropropagation System for Hemp

Hyperhydricity of shoots initiated in vitro, poor shoot extension, inability of shoot cultures to maintain good growth over an extended time, and unsuccessful ex vitro rooting have limited the development of a commercial scale micropropagation system for hemp (Cannabis sativa). We present a culture initiation method that prevents shoot hyperhydricity using vented-lid vessels with 0.2-µm pores and medium containing agar at 1% (w/v). To optimize shoot multiplication in vitro, a control medium (medium A) and four treatment media (medium B, C, D, and E), with varying inorganic nutrients and vitamins were tested. Control medium A consisted of 1× Murashige and Skoog (MS) with vitamins plus 3% (w/v) sucrose, 0.5 mg·L−1 metatopolin, 0.1 mg·L−1 gibberellic acid, and 0.8% agar (w/v) at pH 5.7. The four treatment media differed from the control medium as follows: medium B, 2.5× MS with vitamins; medium C, 1× MS with vitamins plus added mesos [calcium chloride (anhydrous), magnesium sulfate (anhydrous), and potassium phosphate (monobasic) nutrients]; medium D, 1× MS with vitamins plus added vitamins; and medium E, 1× MS with vitamins plus added mesos and vitamins. Medium C and medium E produced more microcuttings than the control at 6 weeks after the initial subculture with shoot multiplication media and all other treatments at 9 and 12 weeks. Shoots grown on these two media displayed optimal extension and leaf lamina development; however, they exhibited slight chlorosis by 12 weeks after subculture with shoot multiplication media. In a separate experiment, medium E was supplemented with ammonium nitrate at 0, 500, 1000, or 1500 mg·L−1, and cultures grown with 500 mg·L−1 produced the most microcuttings and exhibited the best combination of shoot extension and leaf lamina development. We provide a method of prerooting microshoots in vitro that has resulted in 75% to 100% rooting ex vitro in rockwool. Using 10 recently micropropagated plants, ≈300 retip cuttings (cuttings taken from new shoots from recently micropropagated plants) were harvested over 10 weeks. The average weekly rooting was more than 90%. Retipping can produce nine-times as many plants in a similar amount of floor space as stem cuttings derived from traditional stock mother plants. The micropropagation/retipping method proposed can be a more efficient way to generate clonal liner plants for commercial-scale production.

Studies of three apple pollinizer cultivars on m9 clonal rootstock under high-density plantation in cold dry temperate region of Kinnaur, Himachal Pradesh

A field experiment was carried out at the Vegetable Research Station, Kalpa, to study the performance of three pollinizer cultivars grafted on M9 clonal rootstock under high-density plantations in the cold temperate region of Kinnaur, Himachal Pradesh, situated at an altitude of 27,000 meters. The high-density plantation of apples in Kinnaur district is still in the inception stage and it is important to aware the farmers of the area about pollinizer cultivars improve the production of temperate fruits. Sufficient and judicious incorporation of pollinizer cultivars is indeed an important aspect in the enhancement of productivity, keeping in mind that this trial was carried out to benefit the farming community in the coming years. The experiment evaluates three apple cultivars ‘Gale Gala/M9’, ‘Redlum Gala/M9’, and ‘Auvil Early Fuji/M9’, planted in the year 2016 as a feathered plant at a spacing of 2.5X1.0 meters in Randomized Block Design (RBD). Most of the growth and fruiting characteristics were found to be non-significant and significant results were obtained only in the Number of fruits, Fruit Size, Length and fruit weight. However, Maximum, shoot extension growth (13.86 cm), plant height (219.50 cm), Total Number of flowers Number (1211 / tree), Number of fruit set /tree (64.25), Number of fruits/tree (30.17), Yield (3.79 kg/tree) and Productivity (15.14 MT/Ha) were recorded with Redlum Gala on M9, whereas, trunk diameter (30.50 mm), plant spread N-S (120.83 cm), fruit diameter (81.21 mm), percent fruit set (23.06 ) and Fruit Size (Length, 73.77 mm; Breadth 77.68 mm) were observed in Gale Gala on M9. Further, higher Plant Spread E-W (125.00 cm) and fruit weight (218.23 g/fruit) were observed in Auvil Early Fuji. Studies have shown that all three pollinizer cultivars performed similarly with a non-significant difference, yet Redlum Gala/M9 performed better amongst the cultivars studied and it may be recommended to grow under high-density plantations in cold temperate conditions of Kinnaur, Himachal Pradesh.

Establishment of a Micropropagation Protocol for Elite Accessions of Bael (Aegle marmelos (L.) Corr.), a Tropical Hardwood Species

The limited availability of high-quality planting material hinders the popularization of bael (Aegle marmelos (L.) Corr.) as a profitable cash crop in Sri Lanka. Five elite bael accessions, namely, Beheth Beli, Paragammana, Mawanella, Rambukkana, and Polonnaruwa-Supun, have been identified and used for mass propagation through budding and grafting. However, this process gets hampered by the limitations in large-scale production of planting material. Micropropagation is an alternative technique to produce clonal plants in large-scale; however, no established protocol is available for the field-grown elite bael accessions in Sri Lanka, and hence, the present study was conducted. The best sterilization method was found to be the washing of explants in a 2.5% fungicide solution for two hours. The full MS and ½MS media provided significantly similar performance in shooting, as indicated by the measured parameters. The twig plants did better than leaf explants concerning shoot extension, in which twig explants yield 1.33 cm taller shoots. The 1 mg/l of BAP concentration generated the highest number of shoots (6.20) and the most extended shoots (3.83 cm). The most successful rooting (60% success) was spotted with full MS, 1 mg/ml NAA, and 3% sugar. As previously reported, the successful micropropagation is possible if the explants are harvested from April to June, immediately after the fruiting season of the plant. The established protocol can mass-produce clonal bael plants from the elite accessions.

Bioclimatic distance and performance of apical shoot extension: Disentangling the role of growth rate and duration in ecotypic differentiation

Under the same environmental conditions, southern and northern populations of temperate and boreal ecosystems exhibit different growth performance. However, which growth trait drives this difference is still unresolved. This study aimed to disentangle the effect of duration and rate of growth on shoot extension of five black spruce [Picea mariana (Mill.)] populations originating from a latitudinal gradient in Quebec, Canada, and growing in a common garden at the southern border of the boreal forest to simulate warming conditions. Bud phenology was monitored weekly during the growing seasons 2017–2019, and shoot length was recorded in autumn, representing annual growth of the primary meristem. Populations originating from the colder sites showed a lower annual shoot increment compared to those originating from the warmer sites. Despite similar durations of bud phenology, the period of shoot extension occurred between the beginning of June and the beginning of July and was longer in the provenances originating from the colder sites. The period of shoot extension, on average, was shortened by 0.9 days for each degree Celsius of increase in annual mean temperature of the site of origin. Moreover, the populations originating from warmer sites showed higher growth rates, which increased by 0.1 cm day−1 for each degree Celsius of increase in the annual mean temperature of the site of origin. Our results confirmed ecotypic variation in growth performance among black spruce populations and demonstrated that differences in shoot length are related to both rate and duration of growth. In the context of a warming climate, northern populations may be unable to reach the current growth performance of southern ones because of their adaptations to harsh local conditions and low intrinsic growth rates.

Impact of organic and inorganic fertilizers on tree growth and quantitative traits of Kinnow (Citrus nobilis Lour × Citrus deliciosa Tenor)

The continuous application of huge amount of chemical fertilizers degrades the quality, health and productivity of the soil. In future production scenario, use of chemical fertilizers in combination with organic sources of nutrients may play an important role in improving soil health and also helps to sustain optimum production of good quality and quantity of Kinnow. Based on this, the present investigation was carried out during 201518 at Department of Horticulture, Khalsa College, Amritsar (Punjab), to study the impact of various organic and inorganic fertilizers on vegetative growth, fruit physical parameters and yield traits of Kinnow. Treatments were laid out in randomized block design with various combinations of Azotobacter, Phosphate solubilizing bacteria, Vesicular arbuscular mycorrhiza, Trichoderma, Farmyard manure, Azospirillum, vermicompost and inorganic fertilizers based on recommended dose of fertilizers (RDF). It was observed that maximum vegetative growth of annual shoot extension (39.70 cm), trunk girth (6.42 cm), leaf area (30.17 cm2) and tree spread (N-S -13.83% and E-W-15.43%); physical characters like fruit/plant (619.32); yield (102.98 kg/plant), fruit length (6.86 cm), fruit breadth (7.81 cm), fruit weight (233.06 gm), fruit volume (220.55 cc) and juice content (56.36%) were recorded with combination of RDF + VC + PSB + VAM followed by RDF + Azotobacter + PSB + VAM while lower performance was observed in treatment with RDF (100%) alone. Based on this, it was concluded that both organic and inorganic fertilizers improved the physicochemical properties of soils which ultimately helps to improve the vegetative and quantitative traits of fruit plants due to increase in uptake of various nutrients and photosynthates in plant.

Hydraulic safety margins of co-occurring woody plants in a tropical karst forest experiencing frequent extreme droughts

Hydraulic safety margins (HSM) have been widely studied to assess the hydraulic risks and/or strategies of plant species under drought. However, calculations of HSM tend to vary between studies, leading to conflicting conclusions. In this study, HSM of 16 co-occurring woody species (including evergreen trees, brevi-deciduous trees, and lianas) in a tropical karst forest was investigated. They were expressed as: (1) the difference between minimum leaf water potential and water potential causing 50% loss of leaf hydraulic conductance (HSMleaf), (2) the difference between water potential at stomatal closure and that at 50% loss of branch hydraulic conductivity (HSMstomatal), and (3) the difference between water potential at 50% loss of leaf hydraulic conductance and that at 50% loss of branch hydraulic conductivity (HSMsegmentation). We asked the following questions: were HSMleaf in the normal and extreme dry seasons across plant groups different? Were there correlations between different HSM-calculations? Results showed that, on average, the three plant groups showed similar and positive HSMleaf in the normal dry season, but evergreen trees declined to a more negative value in the extreme dry season while the other two groups remained positive. The massive loss of leaf hydraulic conductance in several evergreen tree species was consistent with their extensive shoot dieback under extreme droughts. Across species, there were no significant relationships between HSMstomatal and HSMleaf. Most species (mainly lianas and brevi-deciduous trees) showed negative HSMsegmentation, which did not support the vulnerability segmentation hypothesis that branches are more resistant to cavitation than leaves. Moreover, more negative HSMsegmentation tended to have lower HSMstomatal and larger HSMleaf in the extreme dry season. This study indicates that karst evergreen trees are more likely to experience leaf hydraulic failure under extreme droughts, and reveals potential correlations between branch and leaf hydraulic safety strategies. Further studies on HSM-demographic rate relationship in the tropical karst forests are recommended.

Weed Management in Apple Cv. Royal Delicious by Using Different Orchard Floor management Practices

ABSTRACT In this study, 19-year-old apple orchard at Arabal, Shalimar, Jammu and Kashmir, India, was selected during 2015 and 2016. Forty-five trees were treated with paddy straw mulch, paddy straw mulch followed by glyphosate @ 2.0 l ha−1, oxyflourfen @ 1.0 l ha−1, oxyflourfen @ 1.0 l ha−1 followed by glyphosate @ 2.0 l ha−1, atrazine @ 3.0 kg ha−1, atrazine @ 3.0 kg ha−1 followed by glyphosate @ 2.0 l ha−1, pendimethalin @ 2.0 l ha−1, pendimethalin @ 2.0 l ha−1 followed by glyphosate @ 2.0 l ha−1, bicolor polythene mulch, cowpea, white clover, clean cultivation, farmer practices, zero weeds and control. Three replications were maintained in a randomized complete block design. Minimum weeds (0.0) and weed control efficiency (100%) were recorded in zero weeds, bicolor polythene mulch and in paddy straw mulch followed by glyphosate. High levels of soil nutrients, large annual shoot extension (49.3 and 50.2 cm) and leaf area (77.83 and 78.57 cm−2) with maximum fruit yield (82.03 and 80.60 kg/tree) were recorded in paddy straw mulch followed by glyphosate during 2015 and 2016, respectively. Paddy straw mulch followed by glyphosate can be used for effective weed control with improved yield and growth characters of apple.

Short Shoot Growth and Reproduction Response to Light Conditions Vary with Order Branching in the Proximal Part of C. atlantica Crown

This study compared the effects of shading in individual branch orders 2 and 3 on the needle survival, growth, and reproduction of five categories of short shoots of the proximal part of wild Atlas cedar (Cedrus atlantica (Endl.) G. Manetti ex Carrière). The sun exposure did not affect the number of short shoots in the two branch orders, whereas light compared to shade only stimulates the unbranched short shoot elongation of the branch order 3. The impact of shade exposure compared to sun on the loss of needles depends on the order of branching; it is weak to order 2 and increases to higher order. This effect in the branch order 3 is achieved by a significant decrease of the fallen leaf number in the unbranched short shoot SSnr and the short shoot SS/T worn by Twigs while in the branch order 2 only short shoot SS (nr + r) loses significantly few needles. In terms of short shoot extension and needle loss, the SS/T of the branch order 3 behaves in the same way as the SS (nr + r) of the branch order 2. The shadow compared to sunlit only decreases significantly the production of pollen strobili of the branch order 2. Close relationships between short shoot extension, leaf life span, and pollen strobili production of axillary products in the proximal part of C. atlantica crown were found.

Influence of prohexadione-calcium and paclobutrazol on growth, yield and mineral content of pear cv. Clapp’s favourite

Present investigation was carried out to study the influence of growth retardants viz., prohexadione-calcium and paclobutrazol on mineral content of pear cv. ‘Clapp’s Favourite’ during the year 2015-2016. The experiment was laid out with thirteen treatments, replicated thrice on 12 year-old-pear tree with uniform vigor and health under uniform cultural practices. The treatment comprised of single and double spray of growth retardants i.e., prohexadione-calcium (100 ppm, 200 ppm and 300 ppm) and paclobutrazol (100 ppm, 200 ppm and 300 ppm). The first spray of these growth retardants was given at complete petal fall stage and second at four weeks after first spray. The orchard soil was moderately deep with good fertility status. Results revealed that both the growth retardants had showed a significant influence on the studied characters. The plants sprayed twice with prohexadione-calcium @ 200 ppm (T9S2) recorded minimum annual shoot extension growth of 16.92 cm and leaf area (22.20 cm2) alongwith increase in fruit yield (51.24 kg). Highest value for calcium (Ca) in leaves and fruits of pear (574.00 mg & 71.24 mg, respectively) was recorded when plants were sprayed twice with prohexadione-calcium at 300 ppm. Results also revealed that application of prohexadione-calcium application at 200 ppm sprayed twice (T9S2) resulted in significant increased in potassium content of the pear leaves and fruits i.e. 98.40 mg and 22.78 mg, respectively. However minimum value for potassium content was recorded in control (T1S0). Double spray of prohexadione-calcium @ 200 ppm was effective in reducing the annual extension growth, leaf area and increasing the fruit yield and calcium and potassium content in leaves and fruit.

The flush development of evergreen recurrent flushing perennials: an experimental overview with insights into the flowering of olive

Recurrent flushing perennials are those that grow by episodic waves of shoot extension under conditions continuously favourable for growth. Here we review the habit for evergreen perennials. The commencement of a new flush appears to depend on the stimulation of buds by plant growth regulators. The determination of a new flush as vegetative or floral most likely occurs during early shoot development. Cool temperatures are usually florally inductive, but other factors such as periods of water stress before flush commencement, and low crop loads may also enhance induction. There is little evidence for the control of the final size of vegetative shoots, and even less for the size of floral shoots. The time between successive flushes is cyclic and temperature dependent. New work with olive is presented and shows that pruning increases the proportions of vegetative shoots to develop from comparable nodes of pruned and non-pruned branches. It also shows that immature vegetative flushes on olive branches in winter inhibit flowering to some extent, a result previously shown for other evergreen recurrent flushing trees.

Effect of organic and inorganic mulches on growth, yield and fruit quality of peach cv Redhaven

The present study was carried out on the effect of mulch materials on growth, yield and fruit quality of peach [Prunus persica (L) Batsch] cv Redhaven at experimental block of Department of Fruit Science, Dr YS Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh during 2019-2020. Various types of mulches like grass mulch, black polyethylene mulch, silver red polyethylene mulch, polyethylene mulch, nylon mulch mat and coir mulch were evaluated in this experiment. The results of the study showed that plant growth, yield and fruit quality of peach were significantly affected by all the mulching treatments as compared to control. The maximum increase in tree height, spread, volume, annual shoot extension growth, fruit set, lowest fruit drop, fruit yield, leaf area, leaf chlorophyll content, fruit size, weight and volume were recorded in the plants under black polyethylene mulch which was statistically at par with nylon mulch mat. The maximum fruit quality parameters like total soluble solids, titratable acidity, reducing and non-reducing sugars were recorded under nylon mulch mat.

Stabilising Urea Amine Nitrogen Increases Potato Tuber Yield by Increasing Chlorophyll Content, Reducing Shoot Growth Rate and Increasing Biomass Partitioning to Roots and Tubers

Much of the nitrogen in crop fertiliser is degraded before acquisition. Technologies that stabilise urea-nitrogen minimise this. Degradation also specifically reduces the amount of ureic amine that many fertilisers initially contain, which is important because this nitrogen form has unique beneficial effects on plants. To investigate mechanisms whereby urea stabilisation increases potato tuber yield, we compare effects of foliar applications of chemically stabilised and non-stabilised urea against industry-standard fertiliser, on the physiology, form and yield of greenhouse-grown Casablanca under identical nitrogen supply. Stabilised urea is tested on Rooster and Shelford yields in Irish and British field trials. Stabilised amine nitrogen (SAN) increases Casablanca leaf relative chlorophyll content and initially reduces shoot growth rate. When harvested shortly after tuber initiation, SAN-treated plants have increased root to shoot weight ratios and we find tight negative correlations between shoot growth rate and root weight: large roots and slow shoot extension occur predominantly in SAN-treated plants. SAN increases ratios between initiation-stage tuber weight and (a) shoot length and (b) shoot growth rate. At a second harvest at mid-bulking, SAN increases high-grade Casablanca tuber yielding. At this later stage, yield correlates positively with shoot weight. In the field, SAN increases Rooster canopy greenness and marketable yields of both Rooster and Shelford. Yield improvements specific to this N form when stabilised are suggested to occur through increased photosynthesis and early-stage increases in root to shoot weight ratio. This phenotype then supports increased bulking-stage shoot growth and shoot-sourced resource for tuber growth. Stabilising urea amine induces high-yielding phenotypes with improved internal nitrogen utilisation efficiencies.

Contrasting phenotypes emerging from stable rules: A model based on self-regulated control loops captures the dynamics of shoot extension in contrasting maize phenotypes.

The dynamics of plant architecture is a central aspect of plant and crop models. Most models assume that whole shoot development is orchestrated by the leaf appearance rate, which follows a thermal time schedule. However, leaf appearance actually results from leaf extension and taking it as an input hampers our ability to understand shoot construction. The objective of the present study was to assess a modelling framework for grasses, in which the emergence of leaves and other organs is explicitly calculated as a result of their extension. The approach builds on a previous model, which uses a set of rules co-ordinating the timing of development within and between phytomers. We first assessed rule validity for four experimental datasets, including different cultivars, planting densities and environments, and accordingly revised the equations driving the extension of the upper leaves and of internodes. We then fitted model parameters for each dataset and evaluated the ability to simulate the measured phenotypes across time. Finally, we carried out a sensitivity analysis to identify the parameters that had the greatest impact and to investigate model behaviour. The modified version of the model simulated correctly the contrasting maize phenotypes. Co-ordination rules accounted for the observations in all studied cultivars. Factors with major impact on model output included extension rates, the time of tassel initiation and initial conditions. A large diversity of phenotypes could be simulated. This work provides direct experimental evidence for co-ordination rules and illustrates the capacity of the model to represent contrasting phenotypes. These rules play an important role in patterning shoot architecture and some of them need to be assessed further, considering contrasting growth conditions. To make the model more predictive, several parameters could be considered in the future as internal variables driven by plant status.

Rapid plant responses following relocation of a constructed floating wetland from a construction site into an urban stormwater retention pond

This study compared plant growth, nutrient partitioning and total nutrient uptake by tall sedge (Carex appressa) plants in large-scale Constructed Floating Wetlands (CFWs). Two CFWs with a total area of 2088 m2 were installed in a 2.6 ha man-made urban lake to treat stormwater runoff during the construction phase of a 45-ha residential development. After 12 months of operation, parts of the CFWs, with a total area of 147 m2, were removed from the urban lake and relocated into a well-established 0.127-ha stormwater retention pond at another site. Biomass and nutrient concentrations of C. appressa shoots above the floating mat and roots below the mat were analysed at both sites 12, 16 and 25 months after initial planting. Plants at the urban lake maintained an extensive root network but there was no increase in total plant biomass at 16 and 25 months after planting. In contrast, the relocated plants in the stormwater pond showed extensive shoot growth but a significant decline in root biomass. C. appressa at the urban lake removed and sequestered 1.00 ± 1.04 g m−2 N, 0.11 ± 0.07 g m−2 P and 1.03 ± 0.81 g m−2 K while plants at the pond removed 11.20 ± 2.29 g m−2 N, 1.37 ± 0.26 g m−2 P and 16.13 ± 2.88 g m−2 K during 12 and 25 months after planting. This study demonstrated that C. appressa adapted rapidly to changes in nutrient availability. The implications are interesting as nutrient levels can be low in constructed lakes during the initial phase of urban developments but can increase rapidly as the development progresses. The study demonstrated multiple benefits of CFWs for stormwater treatment during the early construction stages of an urban development and the potential benefits of relocating and establishing CFWs in existing stormwater retention ponds and lakes.

Responses of mature roadside trees to root severance treatments

Conflicts between trees and infrastructure installation or repair occur frequently in the urban environment and may result in damage to or complete removal of tree roots. We monitored the responses of trees to linear root cutting and examined the effects of the presence of a road within tree root zones. Mature Quercus virginiana Mill trees (n = 31) were exposed to three root pruning treatments (plus a control) consisting of a trench on one side of the tree, offset by a distance as a multiple of trunk diameter (3x, 6x and 12x). Roots were severed manually, and their diameters were measured at the cut point to estimate a total cross-sectional area of severed roots. The total severed root cross-sectional area was subsequently expressed as a ratio of whole trunk cross-sectional areas (termed Ar(BH)), as well as trunk conductive sapwood areas (termed As(BH)) at breast height (1.4 m). The shortest horizontal distance between the tree bases and the edge of a nearby road was also recorded and included in statistical analyses as a continuous variable. Linear root cutting reduced shoot extension and leaf area by as much 146.13 mm (p < 0.01) and 2.92 cm2 (p < 0.001) respectively, one growing season after root severance. Trees nearer the road had significantly reduced trunk diameter growth (p < 0.05), independent of root severance effects, i.e. 12x, 6x and 3x treatments. Pre-dawn leaf water potential was negatively affected for all treatments (p < 0.05) and the symptoms of water stress persisted in the 3x treatment for 440 days. Ar(BH) and As(BH) ratios were regressed against physiological (predawn leaf water potential (Ψ), stomatal conductance (gs), leaf temperature (T) and two chlorophyll fluorescence variables (Fv/Fm and Fv/Fo)) and growth (trunk diameter, shoot extension and leaf area) responses. Ar(BH) was a significant predictor of Ψ, Fv/Fm, Fv/Fo, shoot extension and leaf area responses after one growing season, although model strength varied (R2 = 0.75, 0.14, 0.16, 0.18, 0.24 respectively). To avoid sustained water stress symptoms, linear root cutting on Q. virginiana should not be undertaken closer to trees than six times DBH, equating to ≈ 25% root system loss.

The colors of heath flowering – quantifying spatial patterns of phenology in Calluna life‐cycle phases using high‐resolution drone imagery

AbstractRecent developments in high‐resolution ecosystem mapping using unmanned aerial vehicles (UAV) open up promising perspectives for the monitoring of fine‐scale vegetation patterns and ecological functioning. In this study, we examine the potential of UAV imagery to track the structural composition and related phenological traits of the dwarf shrub Calluna vulgaris on a former military training area. On a European Natura 2000 heathland site, habitat management is shown to be evaluated on the basis of flowering dynamics and reproductive recovery as a proxy of functional changes that are generated after fire destruction. In particular, we utilize true color camera information and digital surface models to determine the spatiotemporal evolution of Calluna life‐cycle phases and flowering phenology 2 years after controlled burning. A stepwise methodological framework is presented that extracts Calluna pixels, spatially separates juvenile and mature life‐cycle phases, differentiates between generative and vegetative shoot extension and finally quantifies proportions of flowers, fruits and vegetative growth in two consecutive peak flowering periods. We show that Calluna life‐cycle phases can be spatially differentiated in pioneer, building and mature phases in UAV imagery. In the juvenile phase, regeneration from germination is low (&lt;10%) and sprouting from the stem base dominates recovery patterns after fire management. The study further reveals that the distribution of flowering and fruiting during peak flowering time is spatially heterogeneous with high variations between years. In the fire unaffected mature phase, proportions of flowers and fruits are reduced indicating a decrease in reproductive capacity of unmanaged Calluna stands. A phenological phase shift is detected from flowering to fruiting that is related to an increase of Calluna growth height. The study shows that the functional patterns of growth and reproduction can be mapped for heathland ecosystems using simple true color drone cameras.