Higher Specific Leaf Weight Research Articles

Differences in Water Relations and Physiological Characteristics in Leaves of Wheat Associated with Leaf Position on the Plant

The seasonal change in leaf water potential and its components, stomatal resistance, specific leaf weight, photosynthesis rate, the activities of ribulose-1,5-bisphosphate carboxylase and nitrate reductase, and soluble proteins were measured in flag leaves (ninth from base in position), seventh and fifth leaves of wheat Triticum aestivum L. cv Kalyansona. Flag leaves had a lower water and solute potential and lower or equal turgor pressure than seventh and fifth leaves. These differences were found to be independent of environment. The rate of photosynthesis and nitrate reductase activity were always lower in fifth and seventh leaves than in flag leaf. The photosynthetic efficiency in flag leaves appeared to be associated with lower stomatal resistance and higher specific leaf weight. The relations between leaf water potential and relative water content showed a change with leaf position. This change possibly allows flag leaf to maintain its functional efficiency despite its lower water potential.

Photosynthetic responses to light in seedlings of selected Amazonian and Australian rainforest tree species.

Seedlings of the Caesalpinoids Hymenaea courbaril, H. parvifolia and Copaifera venezuelana, emergent trees of Amazonian rainforest canopies, and of the Araucarian conifers Agathis microstachya and A. robusta, important elements in tropical Australian rainforests, were grown at 6% (shade) and 100% full sunlight (sun) in glasshouses. All species produced more leaves in full sunlight than in shade and leaves of sun plants contained more nitrogen and less chlorophyll per unit leaf area, and had a higher specific leaf weight than leaves of shade plants. The photosynthetic response curves as a function of photon flux density for leaves of shade-grown seedlings showed lower compensation points, higher quantum yields and lower respiration rates per unit leaf area than those of sun-grown seedlings. However, except for A. robusta, photosynthetic acclimation between sun and shade was not observed; the light saturated rates of assimilation were not significantly different. Intercellular CO2 partial pressure was similar in leaves of sun and shade-grown plants, and assimilation was limited more by intrinsic mesophyll factors than by stomata. Comparison of assimilation as a function of intercellular CO2 partial pressure in sun- and shade-grown Agathis spp. showed a higher initial slope in leaves of sun plants, which was correlated with higher leaf nitrogen content. Assimilation was reduced at high transpiration rates and substantial photoinhibition was observed when seedlings were transferred from shade to sun. However, after transfer, newly formed leaves in A. robusta showed the same light responses as leaves of sun-grown seedlings. These observations on the limited potential for acclimation to high light in leaves of seedlings of rainforest trees are discussed in relation to regeneration following formation of gaps in the canopy.

Leaf thickness and response of leaf photosynthesis to water stress in soybean varieties

A comparative study of photosynthetic response to soil moisture was conducted with soybean varieties (Harosoy, Norin No. 1 and Hogyoku). When the plants were grown in May before the rainy season under a high radiation level, per unit leaf area the photosynthetic rate of Harosoy leaves was significantly higher throughout the entire range of soil water potentials and leaf water potentials than that of Norin No. 1 leaves. The high photosynthetic rate of Harosoy under non-stress conditionsaand mild water stress was associated with both the high specific leaf weight and the high leaf areal nitrogen content. The photosynthetic response of the Harosoy leaves developed during rainy season under a low radiation level, however, was similar to that of Norin No. 1; no significant difference was observed between these two varieties in the specific leaf weight and in the leaf areal nitrogen content.

Seasonal Trends in Net Photosynthetic Potential, Dark Respiration, and Specific Leaf Weight of Apple Leaves as Affected by Canopy Position1

Abstract Changes in photosynthetic parameters in ‘Stayman’/Malling Merton (MM) 111 apple (Malus domestica Borkh.) trees measuring 5 m wide and 4 m high were studied for an entire growing season. Parameters investigated included penetration of photosynthetically active radiation (PAR), changes in spur leaf net photosynthetic (Pn) potential, dark respiration (Rd) and specific leaf weight (SLW). As measured by changes in PAR penetration, canopy development was generally complete by mid-May. Pn, Rd, and SLW were modified by canopy position. SLW was influenced by the previous light environment as peripheral canopy leaves had higher SLW’s than interior leaves.

VARIATION IN SPECIFIC LEAF WEIGHT AND RuDPCase ACTIVITY IN MUNGBEAN

Specific leaf weight (SLW) and ribulose 1,5-diphosphate carboxylase (RuDPCase) were determined for 20 mungbean (Vigna radiata (L.) Wilczek) varieties. Varietal difference was significant for SLW and RuDPCase at the early reproductive stage. Significant and positive correlations were also found among SLW, RuDPCase, harvest index (HI), and seed yield. Results imply that high seed yield of mungbean could be associated with high photosynthetic rates and efficient partitioning of photosynthate. It was concluded that increasing seed yield in mungbean should be possible by selecting for (1) high SLW, (2) high HI, and (3) an increased RuDPCase activity.

Photosynthesis, Transpiration, and Ribulose Bisphosphate Carboxylase of Selected Crested Wheatgrass Plants1

AbstractInformation on rates of physiological processes is needed to identify genotypes differing in physiological characteristics for use in varietal improvement programs. Apparent photosynthesis (AP), transpiration (E), stomatal conductance (rc), ribulose bisphosphate Carboxylase (RuBPc), specific leaf weight (SLW), and stoma frequency were measured in diploid, tetraploid, and hexaploid crested wheatgrass [Agropyron cristatum (L.) Gaertn.] plants from Iran to determine rates for these physiological processes in this species. Two named varieties of crested wheatgrass, A. desertorum (Fisch. ex Link) Schult. ‘Nordan’ and A. cristatum ‘Ruff’ were also evaluated.Mean AP rates were 22.0, 12.5, and 12.2 mg CO2 dm‐2 hour‐1 and mean E rates were 2.7, 1.4, and 1.6 g H2O dm‐2 hour‐1 for greenhouse‐grown tetraploid, hexaploid, and diploid plants, respectively. Field‐grown (natural water stress) hexaploid plants had higher AP rates (18.1 and 10.4 mg CO2 dm‐2 hour‐1 in 1976 and 1977, respectively) than did tetraploid plants (13.1 and 8.3). Activity of RuBPc averaged 12.1, 6.9, and 11.0 µmoles CO2/(mg protein)‐1 hour‐1 for greenhouse‐grown hexaploids, tetraploids, and diploid plants, respectively, and 8.7, 7.6, and 7.4 for field‐grown plants. The field soil was a Parshall fine sandy loam (Pachic haploborolls). The fact that tetraploid plants had the higher AP rates and dry matter production under non‐water stress growing conditions in the greenhouse may indicate a greater potential for increased growth and yield as compared with the other plants evaluated in this study. Hexaploids had the higher SLW with the tetraploids and diploids having similar and lower SLW. Stomate frequency was greater for the tetraploids as compared with hexaploid plants.In the greenhouse, the tetraploid plants fixed more CO2 per unit of RuBPc than either the diploid or hexaploid plants. Both greenhouse and field hexaploid plants had high RuBPc activity, but with less range in AP rates than greenhouse (nonstressed) and field (stressed) tetraploid plants which indicated that either stomatal response is sluggish in the hexaploids or that these plants are capable of fixing greater amounts of CO2 under waterstress conditions. The latter quality may indicate greater drought tolerance.

Growth analysis in a reduced leaf mutant of common bean (Phaseolus vulgaris L.)

A comparison between the Royal Red bean variety and a reduced leaf mutant on the basis of growth indices is reported. The mutants has lower leaf area index (LAI) and leaf area duration (LAD) (−43.7%), higher specific leaf weight (SLW) (on the mean +33.3%) and accumulates less dry matter (−7.7%) than the normal genotype. When the net assimilation rate (NAR) is considered, the mutant is superior to the normal (+62.3%). It is concluded that the unit area of the mutant leaves accumulates dry matter more efficiently than that of the corresponding normal variety.

Effects of a Phosphate Defoliant on Cotton Leaves: Water Relations and Free Amino Acids1

The phosphate defoliant DEF (S,S,S‐Tributylphosphorothrithioate) was sprayed on presquaring greenhousegrown cotton (Gossypium hirsutum L.) plants. Plant water status and leaf area data were taken at 3‐hour intervals during the 1st day and daily thereafter. Stomatal diffusion resistance was measured during the 1st day only. Leaves were analyzed for total N, soluble N, and distribution of free amino acids. Little change in any of the parameters measured was noted the 1st day. On subsequent days the DEF‐treated leaves had lower leaf water potential recovery values (predawn measurement) and lower specific weights (fresh weight basis). DEFtreated leaves, however, had a higher specific leaf weight on a dry weight basis. Leaf N percent did not change as a result of the DEF treatment. Soluble N increased up to twice that of the controls by the 3rd day. The distribution of free amino acids in DEF treated leaves was altered. The concentrations of all amino acids except aspartic acid, glutamic acid + glutamine, proline and valine were significantly increased in the DEF treated leaves. The exceptions remained stable or tended to decrease. The results indicated that DEF‐treated leaves may be mobilizing the leaf protein prior to abscission, but that transport out of the leaf is impeded. Further experiments are needed to substantiate this notion.

Direct and Correlated Responses to Selection for Specific Leaf Weight in Reed Canarygrass1

Substantial progress was made by one cycle of selection for high and low specific leaf weight (SLW) in the broadbased germplasm source NCRC1 of reed canarygrass (Phalaris arundinacea L.). In a space‐planted test, populations derived from 48 high and 48 low selections from 1,016 plants of NCRC1 averaged respectively 11% higher and 10% lower in SLW than NCRCI. Average estimates of realized heritability were 0.59 for high and 0.55 for low SLW, indicating a relatively large additive component of genetic variance for this trait. Changes in SLW were accompanied by changes in other leaf characteristics and agronomic components of forage yield. Compared with NCRCI, the high SLW population averaged 11% greater in leaf thickness (LT), 9% higher in COx‐exchange rate (CER), 21% higher in dry weight per tiller, 24% lower in tiller number, and 2% higher in dry matter yield per plant. In contrast, the low SLW population avesaged 7% less, 7 and 8% lower, 16% higher, and 2% lower than NCRCI in those traits, respectively. The low SLW population had the smallest phenotypic variance among plants within plots for all traits except tiller number and weight, with differences among populations being significant in five of 12 instances. Specific leaf weight was positively correlated with LT and CER within populations.

Genetics of Vein and Stomatal Characters in Bromus inermis Leyss.1

A half‐diallel involving seven parental clones of smooth bromegrass (Bromus inermis Leyss.) was used to elucidate the genetic variation of 14 characters, including width, vein number, vein frequency, interveinal distance, stomatal length, stomatal frequency, and the product of stomatal length and frequency for both leaf and sheath, Combining ability analyses showed that general combining ability (GCA) and specific combining ability (SCA) mean square values were significant, with the exception of the GCA mean square values for leaf vein frequency and interveinal distance. The preponderance of additive gene effects was evident from the variance components for vein number on both leaf and sheath, and leaf stomatal characters. High narrow‐sense heritabilities were estimated for these characters. Phenotypic and genotypic correlation coefficients indicated no association between leaf dimension and leaf vein frequency and interveinal distance. Plants with large leaf area, wide leaves, or high specific leaf weight tended to have high vein number, large stomatal size and low stomatal frequency. Selection for high vein frequency and narrow interveinal distance may increase forage yield of both the first harvest and the regrowth. Selection for small stomata on leaf and sheath, and high stomatal frequency on sheath, should improve forage yield of the first harvest.

Variation in RuDPCase Activity in Barley1

Seasonal patterns of ribulose 1,5‐diphosphate carboxylase (RuDPCase), EC4.1.1.39, activity from leaves and awns, specific leaf weight, and total above‐ground dry matter accumulation rate were determined for two barley (Hordeum vulgare L.) genotypes. In general, RuDPCase activity was greatest in young, fully expanded leaves and was lower in each subsequent leaf down the culm. for a given leaf, RuDPCase activity also decreased sharply with increasing age. Specific leaf weight (SLW) did not change with leaf age but upper leaves on a culm had greater specific leaf weights than did lower leaves. The RuDPCase activity in the total plant canopy and in the youngest expanded leaf for both varieties was significantly and positively correlated with the rate of aboveground canopy dry matter accumulation.Twelve barley cultivars chosen to sample a relatively broad genetic background were grown in two controlled environments and a greenhouse. Genotypes differed significantly in RuDPCase activity (dm2 leaf) −1 and (g dry wt) −1 and in SLW. Only RuDPCase activity (dm2 leaf) −1 and SLW were significantly affected by environment. There were no significant genotype by environment interactions for RuDPCase activity (dm2 leaf) −1, for activity (g dry wt) −1, or for SLW. Heritability estimates using the components of variance method were 0.67, 0.56, and 0.74 for RuDPCase activity (dm2 leaf) −1, for activity (g dry wt)−1, and for SLW, respectively. The correlation coefficients for SLW vs. RuDPCase activity (dm2 leaf) −1 and vs. activity (g dry wt)−1 were 0.83, and 0.06, respectively. It was concluded that RuDPCase activity of barley leaves might be increased in two ways: 1. by selecting for high RuDPCase activity (g dry wt) −1 and 2. by selecting for high SLW.

Some Effects of Ringing and Deblossoming Branches of Young Apple Trees on Leaf Composition

Bark rings and blossoms were removed from selected branches of Y-shaped Sunset/M.7 apple trees at full bloom to give the 10 possible combinations of ringed and unringed, deblossomed and cropping branches. Comparisons of leaf areas and dry weight per unit leaf area (specific leaf weight) showed that leaves from ringed branches were smaller and that extension shoot leaves from ringed branches had higher specific leaf weight. Fruiting had little influence on area per leaf but gave lower specific leaf weight than deblossoming. Mineral analyses of leaves from extension shoots in late summer were expressed in terms of unit leaf area and showed significant treatment effects. Ringing both branches reduced the content of mineral elements but ringing only one branch showed smaller effects on nitrogen, phosphorus, and potassium. This suggests that these elements are taken up through the xylem whenever the roots are adequately supplied with nutrients from the branches. Calcium content, on the other hand, was appreciably reduced by any ringing, suggesting that at least some of this element is normally transported in the phloem. There was no evidence in this experiment that low mineral nutrient levels in leaves on ringed branches had been limiting to dry matter production.

Changes in Leaf Area and Specific Leaf Weight of Sugarbeet Leaves during the Growing Season1

The purpose of this investigation was to observe the rate of leaf accretion and changes in specific leaf weight (SLW) of sugarbeet leaves initiated during the latter portion of the growing season. Leaves increased in area at a rapid rate during the first 14 days after leaf emergence. Specific leaf weight changed as the leaves expanded in area. Diurnal changes in SLW may be related to changes in temperature incoming radiation, or translocation rates. Leaves initiated late in the growing season were smaller and had a higher SLW than leaves initiated earlier in the growing season.

Inheritance of Leaflet Size and Specific Leaf Weight in Alfalfa1

The combining abilities for leaflet size and specific leaf weight (SLW) were determined at two different stages of growth in a 7 ✕ 7 diallel cross population of alfalfa (Medicago sativa L.). Both characters were heritable since the general combining ability was larger than either the specific combining ability or the reciprocal effects. Greater genetic variance was observed at an early bud stage than at a late bloom stage. Large differences in SLW were obtained only at an early bud stage. Leaflet size and SLW were not correlated. Genotypes that combined larger leaflet size and higher SLW were identified. Thus both traits would respond to selection in a plant breeding program. The correlation of these characters with forage yield was generally poor.

DIFFERENCES IN LEAF PHOTOSYNTHESIS AND LEAF TRANSPIRATION RATES AMONG SIX COMMERCIAL WHEAT VARIETIES OF WEST PAKISTAN

Mexi-Pak, a modern high yielding semi-dwarf whert variety with high response to fertilization showed higher photosynthetic rate and higher transpiration rate per unit leaf area as compared with old Pakistani varieties. High photosynthetic rate was associated with high transpiration rate, high specific leaf weight and high nitrogen content per leaf area. Percentage of leaf nitrogen content to leaf dry matter was also high in Mexi-Pak.