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Tomatoes require higher irradiance, although the incidence of physiological disorders in fruit increases at high temperatures. Near-infrared (800–2500 nm) (NIR) reflective materials are effective tools to suppress rising air temperatures in greenhouses. We examined the physiological and morphological changes in tomato growth and fruit quality when grown in a high tunnel covered with NIR reflective film (NR) and in another covered with polyolefin film (PO; control). There was no relationship between the fruit cracking rate and mean daytime temperature under NR. The fruit temperature at the same truss was lower and the increase in air temperature was slow under NR. Fruit dry matter (DM) content under NR was also significantly decreased. These findings suggest that the reduction in fruit cracking under NR results from a decrease in fruit DM content as a consequence of lower fruit temperature and a decrease in total DM (TDM). Total fruit yield did not differ, whereas TDM was significantly decreased under NR. This was considered to result from a lower transmitted photosynthetic photon flux density (400–700 nm) (PPFD) and LAI, and lower photosynthetic capacity in single leaves because of a decrease in both total nitrogen and chlorophyll content. We conclude that NR film reduces fruit cracking in exchange for a slight reduction in TDM.

Field experiments were carried out in 2014 and 2015 to characterize the associated attributes responsible for dry matter accumulation in high-yielding soybean. We attempted to create a high-yielding environment by introducing narrow-row planting at two planting densities, using a new cultivar 'Hatsusayaka' and a current leading cultivar 'Sachiyutaka' in an upland experimental field. Dry matter accumulation was assessed in terms of light interception and radiation use efficiency (RUE). Growth analysis was performed to evaluate the crop growth rate (CGR) and the contribution of the net assimilation rate (NAR) and mean leaf area index to CGR. Maximum soybean yields of 590 and 658 g m −2 were obtained for Hatsusayaka and Sachiyutaka, respectively, in 2015 at the high planting density, with the corresponding maximum aboveground dry matter equaling 1463 and 1331 g m −2 and maximum LAI equaling 8.5 and 7.6. Although cumulative intercepted solar radiation was lower than in previous studies, early canopy closure at around the beginning of the flowering stage and very high RUE (1.54 and 1.68 g MJ −2 for Hatsusayaka and Sachiyutaka, respectively) contributed to the high dry matter accumulation. In contrast to the high yield in 2015, continuous excess soil moisture in early August 2014 may have inhibited nodule nitrogen fixation and decreased the nitrogen content, resulting in an extremely high specific leaf area and low leaf greenness, which agrees well with the low NAR during the corresponding period.

Summary Hundreds of single species studies have demonstrated the facility of silicon (Si) to alleviate diverse abiotic stresses in plants. Understanding of the mechanisms of Si‐mediated stress alleviation is progressing, and several reviews have brought information together. A quantitative assessment of the alleviative capacity of Si, however, which could elucidate plant Si function more broadly, was lacking. We combined the results of 145 experiments, predominantly on agricultural species, in a meta‐analysis to statistically assess the responses of stressed plants to Si supply across multiple plant families and abiotic stresses. We interrogated our database to determine whether stressed plants increased in dry mass and net assimilation rate, oxidative stress markers were reduced, antioxidant responses were increased and whether element uptake showed consistent changes when supplied with Si. We demonstrated that across plant families and stress types, Si increases dry weight, assimilation rate and chlorophyll biosynthesis and alleviates oxidative damage in stressed plants. In general, results indicated that plant family (as a proxy for accumulator type) and stress type had significant explanatory power for variation in responses. The consistent reduction in oxidative damage was not mirrored by consistent increases in antioxidant production, indicative of the several different stress alleviation mechanisms in which Si is involved. Silicon addition increased K in shoots, decreased As and Cd in roots and Na and Cd in shoots. Silicon addition did not affect Al, Ca or Mn concentration in shoots and roots of stressed plants. Plants had significantly lower concentrations of Si accumulated in shoots but not in roots when stressed. Meta‐analyses showed consistent alleviation by Si of oxidative damage caused by a range of abiotic stresses across diverse species. Our findings indicate that Si is likely to be a useful fertilizer for many crops facing a spectrum of abiotic stresses. Similarities in responses across families provide strong support for a role of Si in the alleviation of abiotic stress in natural systems, where it has barely been explored. We suggest this role may become more important under a changing climate and more experiments using non‐agricultural species are now needed. Lay Summary

Massive plantation establishment programme in the tropics has led to an ever-increasing demand for good quality planting stock of teak (Tectona grandis L.f.). Although drupe size in teak is positively correlated with seedling growth much less is known about the combined effect of drupe size and time of emergence on the performance of the seedlings. The drupes were divided in 3 diameter categories (i.e. 9-12, 12-15 and 15-18 mm) and the number of germinants were weekly counted for four weeks. The resulted seedlings were planted in poly bags containing rooting medium of soil and sand (1:1 ratio). Results of the study indicated that the seedling emergence was largest during second week irrespective of drupe size. Seedlings from 15-18 mm diameter class drupes recorded the highest seedling attributes followed by 12-15 mm and 9-12 mm classes. However, net assimilation rate and relative growth rate were highest in the seedlings obtained from 9-12 mm class drupes. With a few exceptions, first week emergents recorded the highest seedling attributes followed by second, third and fourth week germinants. Cluster analysis of the seedling attributes identified the seedlings belonging to 15-18 mm drupe size and emerging during first week as superior. But, considering the largest number of drupes in 12-15 mm size class, peak germination during second week after sowing, price of planting stock and cost of nursery operation per unit of planting, second week germinants of 12 – 15 mm size drupes can also be recommended for raising seedlings in plantation programmes of teak.

Summary 565 I. LMA in perspective 566 II. LMA in the field 567 III. Inherent differences 568 IV. Relation with anatomy and chemical composition 570 V. Environmental effects 572 VI. Differences in space and time 577 VII. Molecular regulation and physiology 579 VIII. Ecological consequences 580 IX. Conclusions and perspectives 582 Acknowledgements 582 References 582 Appendices 587

Leaf photosynthetic capacity (light-saturated net assimilation rate, A A ) increases from bottom to top of plant canopies as the most prominent acclimation response to the conspicuous within-canopy gradients in light availability. Light-dependent variation in A A through plant canopies is associated with changes in key leaf structural (leaf dry mass per unit leaf area), chemical (nitrogen (N) content per area and dry mass, N partitioning between components of photosynthetic machinery), and physiological (stomatal and mesophyll conductance) traits, whereas the contribution of different traits to within-canopy A A gradients varies across sites, species, and plant functional types. Optimality models maximizing canopy carbon gain for a given total canopy N content predict that A A should be proportionally related to canopy light availability. However, comparison of model expectations with experimental data of within-canopy photosynthetic trait variations in representative plant functional types indicates that such proportionality is not observed in real canopies, and A A vs. canopy light relationships are curvilinear. The factors responsible for deviations from full optimality include stronger stomatal and mesophyll diffusion limitations at higher light, reflecting greater water limitations and more robust foliage in higher light. In addition, limits on efficient packing of photosynthetic machinery within leaf structural scaffolding, high costs of N redistribution among leaves, and limited plasticity of N partitioning among components of photosynthesis machinery constrain A A plasticity. Overall, this review highlights that the variation of A A through plant canopies reflects a complex interplay between adjustments of leaf structure and function to multiple environmental drivers, and that A A plasticity is limited by inherent constraints on and trade-offs between structural, chemical, and physiological traits. I conclude that models trying to simulate photosynthesis gradients in plant canopies should consider co-variations among environmental drivers, and the limitation of functional trait variation by physical constraints and include the key trade-offs between structural, chemical, and physiological leaf characteristics.

To clarify the agronomic and physiological characteristics of high‐yielding ratoon rice varieties, 14 rice varieties representing two types (high yield in ratoon crop [RH] and low yield in ratoon crop [RL]) were used as experimental materials. Compared with RL, the grain/leaf ratio of RH at the full heading stage in the main crop was lower. Also, the leaf area duration, net assimilation rate (NAR), crop growth rate (CGR), dry matter weight, photosynthetic rate of flag leaf, and root oxidation activity from the full heading to maturity stage in the main crop were higher. The leaf area index (LAI) and dry matter weight at maturity in the main crop were higher in RH than RL, whereas the rates of LAI attenuation, dry matter translocation and dry matter translocation efficiency (DMTE) from full heading to maturity, and harvest index (HI) in the main crop were relatively lower. The CGR, NAR, dry matter weight from full heading to maturity, and dry matter weight and root oxidation activity at maturity in the main crop were significantly and positively correlated with the yield of the ratoon crop. The rate of LAI attenuation and DMTE from full heading to maturity, grain/leaf ratio at full heading, and HI in the main crop were significantly and negatively correlated with the yield of the ratoon crop. Rational utilization of these agronomic and physiological characteristics would be helpful to screening and breeding high‐yielding rice varieties for ratoon production. Core Ideas The agronomic and physiological characteristics of high‐yielding ratoon rice are clarified. High‐yielding ratoon rice had low grain/leaf ratio at the full heading stage of the main crop. High‐yielding ratoon rice had strong photosynthetic capacity at the late growth stage of the main crop. High‐yielding ratoon rice had low dry matter translocation efficiency at maturity of the main crop. Leaves and roots were highly physiologically active at the late growth stage of the main crop.

In recent decades, nano-scale zero valent iron is reported to have plant growth enhancement capacity under laboratory conditions, but till date, there is no report to highlight its effect on the growth and yield of field-grown plants. In this study, we have evaluated the potential of nZVI priming on rice yield. A two-year field study has been conducted with different concentrations (10, 20, 40, and 80 mg l−1) of nZVI for seed priming. The efficacy of nanopriming was compared with the hydroprimed control set. Seeds were treated for 72 h and sown in nursery beds and after 30 days seedlings were transplanted in the field. Root anatomy and morphology were studied in 7 days old seedlings where no changes were found. RAPD analysis also confirmed that low doses of nZVI were not genotoxic. Nanoprimed plants also had broader leaves, higher growth, biomass, and tiller number than control plants. Maximum yield was obtained from the 20 mg l−1 nZVI primed set (3.8 fold higher than untreated control) which is achieved primarily because of the increase in fertile tiller numbers (two fold higher than untreated control). Higher values of other agronomic parameters like growth rate, net assimilation rate proved that nZVI priming enhanced photosynthetic efficiency and helped in the proper storage of photo-assimilates. All these attributed to increased accumulation of phytochemicals like starch, soluble sugar, protein, lipid, phenol, riboflavin, thiamine, and ascorbic acid in the grains. The elemental analysis confirmed that nZVI priming also promoted higher accumulations of macro and micronutrients in grains. Thus, nanoprimed seeds showed better crop performance compared to the traditional hydropimed seeds. Hence, nZVI can be considered as ‘pro-fertilizer’ and can be used commercially as a seed treatment agent which is capable of boosting plant growth and yield along with minimum interference to the soil ecosystem.

Costs of plant defense are a key assumption in evolutionary ecology, yet their detection has remained challenging. Here we introduce a novel method for quantifying plant growth using the common milkweed Asclepias syriaca and repeated non‐destructive size measurements to experimentally test for costs of defensive traits. We estimated mechanistic components of plant growth (relative growth rate, net assimilation rate, specific leaf area and leaf‐mass ratio) at two levels of fertilization (high and low), and related them to production of toxic cardenolides and exudation of sticky latex. We found negative genetic correlations between cardenolides and growth (most strongly with net assimilation rate) at both nutrient levels. Additionally, plants varied in their cardenolide response to low nutrients, and genetic families maintaining higher cardenolide production at low nutrient availability suffered proportionally larger reductions in growth. In contrast, the amount of latex was positively correlated with plant growth. Because latex is instantly deployed from a plant‐wide system of pressurized laticifers, larger plants may simply exude proportionally more latex when damaged and thus plant size is likely to mask potential costs of latex synthesis. Unbiased quantification of mechanistic growth processes, coupled with the manipulation of nutrient or stress levels, is thus an effective approach to demonstrate allocation to defense and tradeoffs with growth, especially in long‐lived plant species.

• Growth rates vary widely among plants with different strategies. For crops, evolution under predictable and high-resource environments might favour rapid resource acquisition and growth, but whether this strategy has consistently evolved during domestication and improvement remains unclear. • Here we report a comprehensive study of the evolution of growth rates based on comparisons among wild, landrace, and improved accessions of 19 herbaceous crops grown under common conditions. We also examined the underlying growth components and the influence of crop origin and history on growth evolution. • Domestication and improvement did not affect growth consistently, that is growth rates increased or decreased or remained unchanged in different crops. Crops selected for fruits increased the physiological component of growth (net assimilation rate), whereas leaf and seed crops showed larger domestication effects on morphology (leaf mass ratio and specific leaf area). Moreover, climate and phylogeny contributed to explaining the effects of domestication and changes in growth. • Crop-specific responses to domestication and improvement suggest that selection for high yield has not consistently changed growth rates. The trade-offs between morphophysiological traits and the distinct origins and histories of crops accounted for the variability in growth changes. These findings have far-reaching implications for our understanding of crop performance and adaptation.