The rice OsDIL gene plays a role in drought tolerance at vegetative and reproductive stages

Drought is one of the critical factors limiting reproductive yields of rice and other crops globally. However, little is known about the molecular mechanism underlying reproductive development under drought stress in rice. To explore the potential gene function for improving rice reproductive development under drought, a drought induced gene, Oryza sativa Drought-Induced LTP (OsDIL) encoding a lipid transfer protein, was identified from our microarray data and selected for further study. OsDIL was primarily expressed in the anther and mainly responsive to abiotic stresses, including drought, cold, NaCl, and stress-related plant hormone abscisic acid (ABA). Compared with wild type, the OsDIL-overexpressing transgenic rice plants were more tolerant to drought stress during vegetative development and showed less severe tapetal defects and fewer defective anther sacs when treated with drought at the reproductive stage. The expression levels of the drought-responsive genes RD22, SODA1, bZIP46 and POD, as well as the ABA synthetic gene ZEP1 were up-regulated in the OsDIL-overexpression lines but the ABA degradation gene ABAOX3 was down-regulated. Moreover, overexpression of OsDIL lessened the down-regulation by drought of anther developmental genes (OsC4, CYP704B2 and OsCP1), providing a mechanism supporting pollen fertility under drought. Overexpression of OsDIL significantly enhanced drought resistance in transgenic rice during reproductive development, while showing no phenotypic changes or yield penalty under normal conditions. Therefore, OsDIL is an excellent candidate gene for genetic improvement of crop yield in adaption to unfavorable environments.     

Physiological and biochemical characterization of NERICA‐L‐44: a novel source of heat tolerance at the vegetative and reproductive stages in rice

The predicted increase in the frequency and magnitude of extreme heat spikes under future climate can reduce rice yields significantly. Rice sensitivity to high temperatures during the reproductive stage is well documented while the same during the vegetative stage is more speculative. Hence, to identify and characterize novel heat‐tolerant donors for both the vegetative and reproductive stages, 71 rice accessions, including approximately 75% New Rice for Africa (NERICAs), were phenotyped across field experiments during summer seasons in Delhi, India, and in a controlled environment study at International Rice Research Institute , Philippines. NERICA‐L‐44 (NL‐44) recorded high seedling survival (52%) and superior growth and greater reproductive success exposed to 42.2°C (sd ± 2.3) under field conditions. NL‐44 and the heat‐tolerant check N22 consistently displayed lower membrane damage and higher antioxidant enzymes activity across leaves and spikelets. NL‐44 recorded 50–60% spikelet fertility, while N22 recorded 67–79% under controlled environment temperature of 38°C (sd ±1.17), although both had about 87% fertility under extremely hot field conditions. N22 and NL‐44, exposed to heat stress (38°C), had similar pollen germination percent and number of pollen tubes reaching the ovary. NL‐44 maintained low hydrogen peroxide production and non‐photochemical quenching (NPQ) with high photosynthesis while N22 avoided photosystem II damage through high NPQ under high‐temperature stress. NL‐44 with its reproductive stage resilience to extreme heat stress, better antioxidant scavenging ability in both vegetative tissue and spikelets and superior yield and grain quality is identified as a novel donor for increasing heat tolerance at both the vegetative and reproductive stages in rice.     

Differential proline metabolism in vegetative and reproductive tissues determine drought tolerance in chickpea

Proline is emerging as a critical component of drought tolerance and fine tuning of its metabolism under stress affects the plants sensitivity and response to stress. Thus the study was carried out to analyse the effect of water deficit on the proline content and principal enzymes involved in its synthesis (Δ¹-pyrolline-carboxylate synthetase) and catabolism (proline dehydrogenase) at different developmental stages and in different organs (roots, nodules, leaves, pod wall, and seeds) of two chickpea (Cicer arietinum L.) cultivars differing in drought tolerance (drought tolerant ICC4958 and drought sensitive ILC3279). It was observed that increased Δ¹-pyrolline-carboxylate synthetase activity under moderate stress in roots and nodules of ICC4958 caused an increase in proline content during initiation of reproductive development whereas increased proline dehydrogenase activity in nodules and leaves at this period helped to maintain reducing power and energy supply in tissues and proper seed development as seed biomass increased consistently up to maturity. On the other hand, roots and nodules of ILC3279 responded to stress by increasing proline content after the developmental phase of reproductive organs was over (near maturity) which negatively affected the response of pod wall to stress. Concurrent increase in activities of Δ¹-pyrolline-carboxylate synthetase and proline dehydrogenase in pod wall of ILC3279 aggravated the oxidative stress and affected seed development as seed biomass initially increased rapidly under stress but was unaffected near maturity.     

Age at flowering differentially affects vegetative and reproductive responses of a determinate annual plant to elevated carbon dioxide

Plant population and community dynamics may be altered by increasing atmospheric CO(2) concentrations [[CO(2)]] through intraspecific variation in the responses of vegetative and reproductive growth. Although these responses may be regulated by age at flowering, little is known about the direct effects of age at flowering on growth responses to elevated [CO(2)]. In this study, we examined the interactive effects of elevated [CO(2)] and age at flowering on absolute and relative allocation to vegetative and reproductive growth in the determinate, short-day species Xanthium strumarium L. (common cocklebur). Six cohorts were planted at 5-day intervals in chambers maintained at either 365 or 730 micro mol mol(-1) CO(2), with an 18-h photoperiod and a non-limiting nutrient supply. All plants were simultaneously induced to flower by switching the photoperiod to 12 h for 2 days, then switching back to an 18-h photoperiod for the remainder of the experiment. All plants were harvested 15 days after the onset of flowering. Total plant biomass increased 11-41% with increasing [CO(2)] and 45% from the youngest to the oldest cohort. Vegetative growth responses to elevated [CO(2)] significantly increased with increasing age at flowering, associated with increasing sink relative to source capacity. In contrast, total fruit mass decreased 32% from the youngest to the oldest cohort and was not significantly affected by CO(2) supply. Relative biomass allocation to fruit decreased 47% from the youngest to the oldest cohort, reflecting decreased numbers of fruit, and 6-28% with increasing [CO(2)], reflecting decreased mean mass per mature fruit. Our findings suggest that elevated [CO(2)] may increase vegetative growth in Xanthium without increasing reproductive biomass, and that age at flowering may influence these responses through effects on source:sink balance. Further, changes in the allometric relationship between vegetative and reproductive growth associated with growth in elevated [CO(2)] suggest that long-term population and community-level responses to elevated [CO(2)] may differ substantially from predictions based on vegetative responses.     

Comparative analysis of expressed sequence tags (ESTs) from Triticum monococcum shoot apical meristem at vegetative and reproductive stages

Triticum monococcum has recently drawn the attention of biologists to discover and utilize novel genes and alleles. To explore the molecular features of the genetic network governing floral transition in shoot apical meristem (SAM) of spring growth habit T. monococcum, two expressed sequence tag (EST) libraries containing 3,031 ESTs from vegetative SAM (VS) and 2,647 ESTs from early reproductive SAM (RS) were analyzed. Assembly of ESTs resulted in 2,303 unigenes for VS library (368 contigs and 1,935 singletons) and 1,890 unigenes (337 contigs and 1,553 singletons) for RS library. The 67.05 % of VS unigenes and 66.30 % of RS unigenes showed significant similarity with genes of known, putative and or unknown function, whereas the remaining 32.95 % of the VS unigenes and 33.7 % of RS unigenes displayed no significant match with the public protein database. The 1,064 and 866 unigenes of VS and RS libraries were assigned to functional categories using Pageman ontology tool. Further analysis revealed that the switch from VS to RS caused significant changes in the abundance of unigenes assigned to some functional categories. A total of 37 genes were identified which were significantly differentially expressed between vegetative and reproductive stages of T. monococcum SAM. Investigation of the differentially expressed genes revealed the importance of the genes involved in energy metabolism, ubiquitin/26S proteasome system, polyamines biosynthesis and signaling of reactive oxygen species in SAM differentiation towards floral transition in T. monococcum.     

Phytoremediation efficiency of Brassica juncea cultivars at vegetative and reproductive growth stages under individual and combined treatment of fluoride and aluminium

The objective of this study was to investigate phytoremediation ability of Brassica juncea cultivars for aluminium (Al) and fluoride (F) independently and in combination (Al + F). Out of 8 cultivars which were treated with Al, F, and (Al + F), 4 cultivars (Bio-902, Pusa-Tarak, CS-14, and Laxmi) were selected for further studies on the basis of growth parameters. These cultivars were exposed to soil (pH 5) supplemented with F (0, 25, 50, and 75 mg kg^?1) and Al (0, 50, 100, and 150 mg kg^?1) independently and in combination (Al + F) (0 + 0, 50 + 25, 100 + 50, and 150 + 75 mg kg^?1). We found that the accumulation of F, Al, and (Al + F) was highest in the roots followed by grains, shoots, and leaves. When the plants were treated with Al or F separately, the accumulation of Al or F were less as compared to when treated in combination (Al + F). Conclusively, the results also showed that maximum tolerance index, uptake, and translocation factor for F were highest in CS-14, Al in Bio-902, and (Al+ F) in Pusa-Tarak, and were found to be the lowest in Laxmi.     

A rapid,controlled-environment seedling root screen for wheat correlates well with rooting depths at vegetative,but not reproductive,stages at two field sites

Background and Aims

Root length and depth determine capture of water and nutrients by plants, and are targets for crop improvement. Here we assess a controlled-environment wheat seedling screen to determine speed, repeatability and relatedness to performance of young and adult plants in the field.

Methods

Recombinant inbred lines (RILs) and diverse genotypes were grown in rolled, moist germination paper in growth cabinets, and primary root number and length were measured when leaf 1 or 2 were fully expanded. For comparison, plants were grown in the field and root systems were harvested at the two-leaf stage with either a shovel or a soil core. From about the four-leaf stage, roots were extracted with a steel coring tube only, placed directly over the plant and pushed to the required depth with a hydraulic ram attached to a tractor.

Key Results

In growth cabinets, repeatability was greatest (r = 0·8, P < 0·01) when the paper was maintained moist and seed weight, pathogens and germination times were controlled. Scanned total root length (slow) was strongly correlated (r = 0·7, P < 0·01) with length of the two longest seminal axile roots measured with a ruler (fast), such that 100–200 genotypes were measured per day. Correlation to field-grown roots at two sites at two leaves was positive and significant within the RILs and cultivars (r = 0·6, P = 0·01), and at one of the two sites at the five-leaf stage within the RILs (r = 0·8, P = 0·05). Measurements made in the field with a shovel or extracted soil cores were fast (5 min per core) and had significant positive correlations to scanner measurements after root washing and cleaning (>2 h per core). Field measurements at two- and five-leaf stages did not correlate with root depth at flowering.

Conclusions

The seedling screen was fast, repeatable and reliable for selecting lines with greater total root length in the young vegetative phase in the field. Lack of significant correlation with reproductive stage root system depth at the field sites used in this study reflected factors not captured in the screen such as time, soil properties, climate variation and plant phenology.     

Density-dependent reproductive and vegetative allocation in the aquatic plant Pistia stratiotes (Araceae)

Pistia stratiotes is an aquatic macrophyte that grows in temporary-ponds in the southern Pantanal, Brazil. It reproduces both sexually and asexually and is usually observed forming dense mats on the water surface, a condition favored by the plant's vegetative reproduction coupled with an ability for rapid growth. In this study we examined the effect of densely crowded conditions on the production of reproductive and vegetative structures. In addition, we verified whether there is a trade-off between clonal growth and investment in sexual reproductive structures, and whether there is an allocation pattern with plant size. Individual plant biomass and the number of the rosettes producing sexual reproductive structures and vegetative growth structures both increased with density. Increase in plant size resulted in increased proportional allocation to sexual reproductive structures and vegetative growth structures. Allocation of biomass to reproduction did not occur at the expense of clonal growth. Thus, the density response appears as a increase of rosettes producing sexual reproductive structures and vegetative growth structures. Therefore, long leaves and stolons may be adaptive under densely crowded conditions where competition for light is intense. An important aspect in the study of trade-offs is the size-dependency of the allocation patterns .Usually, larger plants produce more biomass. Therefore, larger plants can allocate more biomass to both vegetative and sexual reproduction than smaller plants and thus show a positive correlation between both traits rather than the expected negative one.     

Studies on heat tolerance at rest and orthostatic heat tolerance in a hot environment

Twelve young male Japanese were exposed to a hot environment in summer, and changes in systolic blood pressure induced by changing the position from recumbent to sitting were observed. Sweating was induced in a climatic chamber at 30 degree C with 70% relative humidity by immersing both legs up to the knees into a water bath of 42 degree C for 90 min after sitting on a chair at rest for 30 min in the chamber. The mean values of rise in rectal temperature, body weight loss and mean sodium concentration in sweat were 0.62 degree C, 0.67 kg and 46 mEq/l, respectively. The mean values of fall in systolic blood pressure associated with changing posture and its recovery time were 13.7 mm Hg and 77.5 sec, respectively. Heat tolerance at rest was assessed by a numerical heat tolerance index involving relative water loss, relative rise in rectal temperature, and relative salt loss. Values of relative water loss, relative rise in rectal temperature, and the numerical heat tolerance index correlated closely to those of fall in systolic blood pressure and its recovery time.     

小麦种质芽期和苗期的耐盐性鉴定评价

【目的】研究不同来源小麦种质资源的耐盐性差异,筛选耐盐性较好的品种（系）,探索不同生育期小麦耐盐性鉴定的适合盐浓度,为小麦耐盐鉴定及耐盐小麦品种选育提供参考。【方法】对来源不同的293份小麦种质,在1.5%NaCl盐溶液下进行盐胁迫处理,调查各种质的芽期相对盐害指数;选择芽期相对耐盐指数小于40%的24份小麦资源,在苗期进行不同盐浓度胁迫鉴定,测量不同处理的根长及苗高相对生长率。【结果】筛选出16份芽期相对盐害指数小于20%的高耐盐种质和42份芽期相对盐害指数20-40%耐盐的小麦种质;苗期鉴定表明1.0% NaCl盐浓度为合适的筛选浓度、根长相对生长率为适合的苗期耐盐性鉴定指标,以此为鉴定技术筛选出了Marmin-Minhardi譎44-Minturki和花树蒲两份芽期及苗期均表现耐盐的优异小麦种质;【结论】来源不同的小麦资源中芽期综合耐盐性大小依次为地方品种>国外引进品种>中间试验品系;Marmin-Minhardi譎44-Minturki和花树蒲两份耐盐小麦种质可作为小麦耐盐育种新种质。     

Abundances of thrips on plants in vegetative and flowering stages are related to plant volatiles

Western flower thrips (WFTs), Frankliniella occidentalis Pergrande, and onion thrips (OTs), Thrips tabaci Lindeman, are two cosmopolitan insect pests of agricultural and horticultural plants. Understanding the occurrence and development of thrips on plants is crucial for identifying suitable plants that can be used for developing a “push-pull” strategy against thrips. In this study, the dynamics of WFTs and OTs on plants (Allium fistulosum L., Medicago sativa L., Luffa cylindrica (L.) Roem., Ocimum basilicum L., and Schizonepeta tenuifolia (Benth.) Briq.) were investigated for two consecutive years (2018–2019). Throughout the survey, the abundances of both thrips species were strongly associated with plant species and plant phenology; both thrips species were present at relatively high densities on M. sativa but very low densities on O. basilicum and S. tenuifolia. Populations of both thrips species greatly increased during plant flowering. A Y-tube olfactory test was used to study the effects of plant volatiles in mediating thrips behaviour and showed that volatiles of M. sativa were attractive to both thrips species whether emitted by the plant in the vegetative or flowering stage, while volatiles of O. basilicum and S. tenuifolia were repellent to thrips. Additionally, because of the presence of a high number of floral chemicals, both thrips species exhibited a greater preference for volatiles emitted by plants in the flowering period over those emitted by plants in the vegetative period. Our observations indicate that plant species and flowering status play an important role in the abundance dynamics of thrips and that the volatiles of flowering plants attract thrips more strongly than volatiles emitted by vegetative plants. These findings can facilitate the screening of attractive/unattractive plants for developing push-pull strategies to control thrips.     

Freezing tolerance of chickpea: biochemical and molecular changes at vegetative stage

The aim of this study was to find a correlation between the freezing tolerance of three chickpea (Cicer arietinum L.) cultivars (?nci, I??k-05, and Sar?-98) and their wild relative C. echinospermum and physiological responses. Chickpea plants (15-d-old) were subjected to cold acclimation (CA) (10 °C for 7 d), freezing (-3 or -5 °C for 2 h), and subsequent rewarming (25 °C for 7 d). In two separate experiments with three replications, we determined growth, water status, photosystem 2 photochemical activity, photosynthetic pigments, H₂O₂, malondialdehyde, and proline content, relative leakage ratio, antioxidant enzyme activities, and gene expressions in cultivars different in freezing tolerance. Freezing temperatures adversely affected all the physiological parameters of all cultivars. Rewarming did not lead to complete recovery. The cultivar ?nci was more tolerant to the freezing temperatures than others.     

Plasticity of reproductive components at different stages of development in the annual plant Thlaspi arvense L.

Summary This study examines the effect of different densities and the removal of all neighbours at different stages of development on all components of reproduction in the inbreeding annual Thlaspi arvense L. A 64-fold increase in density significantly reduced all repooductive components. The number of flower buds per plant was decreased most strongly; the order of decreasing plasticity among the other components was number of capsules per flower, individual seed weight, ovule number per capsule, flowers per flower bud and seeds per ovule. Removing neighbours at all stages of development increased seed yield of plants in comparison to the control without density reduction, but patterns of plasticity depended strongly on time of treatment. The main effect of the removal of neighbours at the vegetative stage was to increase the number of flowers per plant, but the number of ovules per capsule and seed weight increased also, and abortion of capsules decreased. Removing neighbours at the onset of flowering initially failed to affect flower number per plant, instead it resulted in a strong reduction of capsule abortion and an increase in seed weight. However, several weeks after flowering had initially ceased, fresh lateral inflorescences were produced, resulting in a second flush of reproduction. Removing neighbours at the stage of fruit ripening resulted at first only in an increase in seed witht, but later a second reproductive phase occurred. Fresh lateral branches were produced, but the apical meristem was also reactivated. The overall pattern of plasticity among all reproductive components in response to a removal of neighbours was the same as in response to density. The position of a capsule along the inflorescence influenced its number of ovules, the rate of seed abortion and the mean weight of seeds, with the type of effect depending on the developmental stage at which neighbours were removed. Significant negative correlations were found between the mean weight of seeds and the number of seeds in a capsule under all treatments.     

黄瓜萌芽期和苗期耐冷性评价

选用13份黄瓜材料,研究萌芽期和苗期共12个指标与黄瓜耐冷性的关系,对材料进行耐冷性评价.结果表明:17℃下的相对发芽率、相对发芽势、相对胚根长和相对活力指数在13份黄瓜材料中差异显著(P＜0.05),并与黄瓜耐冷性的相关关系显著;苗期4℃处理2d时各材料之间生理差异明显,冷害指数与恢复后成活率的相关性显著,而与总蛋白、电导率、超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性的相关性不显著.通过聚类分析将黄瓜材料耐冷性分为3个等级,通过逐步回归分析建立了两个生育期黄瓜耐冷性方程,可根据置信区间估计值对黄瓜的耐冷性进行较好的评价.     

Effect of Ppd-1 on the expression of flowering-time genes in vegetative and reproductive growth stages of wheat

The photoperiod sensitivity gene Ppd-1 influences the timing of flowering in temperate cereals such as wheat and barley. The effect of Ppd-1 on the expression of flowering-time genes was assessed by examining the expression levels of the vernalization genes VRN1 and VRN3/WFT and of two CONSTANS-like genes, WCO1 and TaHd1, during vegetative and reproductive growth stages. Two near-isogenic lines (NILs) were used: the first carried a photoperiod-insensitive allele of Ppd-1 (Ppd-1a-NIL), the other, a photoperiod-sensitive allele (Ppd-1b-NIL). We found that the expression pattern of VRN1 was similar in Ppd-1a-NIL and Ppd-1b-NIL plants, suggesting that VRN1 is not regulated by Ppd-1. Under long day conditions, VRN3/WFT showed similar expression patterns in Ppd-1a-NIL and Ppd-1b-NIL plants. However, expression differed greatly under short day conditions: VRN3/WFT expression was detected in Ppd-1a-NIL plants at the 5-leaf stage when they transited from vegetative to reproductive growth; very low expression was present in Ppd-1b-NIL throughout all growth stages. Thus, the Ppd-1b allele acts to down-regulate VRN3/WFT under short day conditions. WCO1 showed high levels of expression at the vegetative stage, which decreased during the phase transition and reproductive growth stages in both Ppd-1a-NIL and Ppd-1b-NIL plants under short day conditions. By contrast to WCO1, TaHd1 was up-regulated during the reproductive stage. The level of TaHd1 expression was much higher in Ppd-1a-NIL than the Ppd-1b-NIL plants, suggesting that the Ppd-1b allele down-regulates TaHd1 under short day conditions. The present study indicates that down-regulation of VRN3/WFT together with TaHd1 is the cause of late flowering in the Ppd-1b-NIL plants under short day conditions.     

The mitochondria ofPolytoma papillatum at two different stages of the vegetative cell cycle

Summary The examination of adjacent sections ofPolytoma papillatum cells by the electron microscope enabled us to construct three dimensional models of the chondriomes. These reconstructions show that in two predivision cells the chondriome primarily consists of one large and highly convoluted mitochondrion. One and three small ovoid mitochondria also exist. Examination of two new daughter cells reveales 30 and 47 mitochondria of various shapes and sizes. This indicates that during the growth phase ofPolytoma (vegetative cell cycle) preponderantly one mitochondrion is formed by fusion of those numerous mitochondria found after cell cleavage. Our observations will be compared with results on this subject in other organisms.We are greatly indebted to Prof. Dr. C. G.Arnold (Erlangen) for his support in this work.