Effects of plant density and nutrient levels on fruit polymorphism in Atriplex sagittata

Atriplex sagittata is a heterocarpic species producing three types of fruits which differ in morphology and ecological properties. This study focused on variation in biomass allocation into particular fruit types under different density and fertilization levels. The reduction in total weight under stressful conditions was accompanied by a reduction of reproductive structures in terms of both total fruit production and mean fruit weight. Allocation of biomass to particular fruit types under different density-fertilization treatments showed considerable variation. The non-dormant, bracteolate fruit type (termed C) contributed 80–90% to the total fecundity and its production was not affected by density-fertilization treatments. The production of this fruit type is higher in the upper part of the maternal plant stem. Production of the very dormant ebracteate fruit type (termed A) increased under favourable conditions and was greater on the lower part of the stem, whereas more of the so-called type B fruit (covered by bracteoles and exhibiting dispersal and dormancy characteristics intermediate between types A and C) was produced under suboptimal conditions and was concentrated in the middle part of the plant body. This pattern contradicts to some extent the theory that deeply dormant and less dispersible fruits will be produced under stressful conditions and may be considered a new model for the behaviour of plants with more than two heterocarpic fruits. The type B fruit, intermediate in both morphology and ecological behaviour, provides a continuum between extreme strategies. Received: 8 February 1998 / Accepted: 19 November 1998     

Changes in Kinetic Characteristics of the ABA Binding Protein(s) of the Grapevine Fruit During Its Developmental Process

By using the micro-volume radio-ligand binding essay (MRLB), the changes in the kinetic characteristics of the ABA binding protein (s) of the Kyoho grapevine (V/t/s vinifera × V. labrusca) fruits during the different stages of fruit development have been studied. The changes in the berry volume growth, concentration of sugar, organic acids and ABA in fruit mesocarp have been determined especially for the studies of ABA-binding protein. The dissociation constant (Kd) and ABA-binding maximum volumes (Bronx)were determined by the Scatchard plots for the ABA-binding protein (s) in microsomes of the fruits. They were: Kd =17.5, 50. 0, 6.3, 13.3 nmol/L: Bmax=98.6, 523.0, 41.6, 85. 4 pmol/g protein respectively for the fruit developmental phase Ⅰ , Ⅱ, veraison and phase Ⅲ. The Scatchard plots showed a rectilinear function for all of the developmental phases including veraison, which suggests in the fruit microsomes at the same developmental phase, the existence of either one kind of the same or several different kinds of ABA-binding sites of identical or similar kinetic characteristics and of high affinity. In different developmental stages, however, changes of the protein at the ABA-binding sites might occur. The binding affinity of ABA-binding protein (s) for ABA was showed to be higher at veraison stage than in other developmental phases and this binding affinity increased nearly by 10 times from the phase Ⅱ to veraison, whereas the concentration (Bmax) of the ABA-binding protein (s) decreased to the minimum at veraison. The reason why such low concentration of ABA at veraison is capable to trigger the onset of fruit ripening might be due to the increase of the affinity of ABA-binding protein (s) for ABA at this time. The possible functions of the ABA-binding protein (s) for fruit development during the different developmental stages were discussed, and it is suggested that the protein (s) detected could be the putative receptor (s) or carrier (s) for the action of this plant hormone in grapevine.     

猕猴桃果实成熟进程中木葡聚糖内糖基转移酶mRNA水平的变化

以中华猕猴桃（ActinidiachinensisPlanch．）果实为试材,木葡聚糖内糖基转移酶（XET）cDNA为探针,研究果实成熟进程中XETmRNA的变化规律,探讨XET在果实后熟软化过程的作用。结果表明,20℃下外源乙烯处理可促进XETmRNA的积累,且这种效应因乙烯处理时间的加长而加强,进而加速了果实软化;0℃处理可抑制XETmRNA的增加,延缓果实软化,但当果实转入20℃后熟时,果实硬度迅速下降,而XETmRNA水平变化不明显。认为XET可能只是一种诱导酶,由它引起的细胞壁解聚并非是猕猴桃果实后熟软化的关键因子。     

高氧对果蔬采后生理影响研究进展

高氧（21%-100%O2）贮藏是近几年发展起来的果蔬采后处理技术之一.概述了高氧对果蔬采后生理如呼吸作用、乙烯合成、组织褐变、活性氧代谢及抗氧化能力、风味等方面的影响,还介绍了高氧对病原微生物生长和采后果蔬腐烂控制的作用.     

果实类型多样性的形成机制和进化

果实是被子植物特有的繁殖器官,果实的类型影响种子传播的模式、有效性和距离。果实类型的多样性在一定程度上造成了不同植物类群在生态上的差异,并对被子植物的进化速度和分化模式产生重要影响。本文对果实类型多样性形成中起关键作用的通路及其进化机制进行了综述,讨论了影响果实类型进化的各种因素,介绍了有关果实类型进化方向和模式的研究进展,为研究被子植物果实多样性的形成和演化提供新的思路。     

A phenological hypothesis on the thermophilous distribution of Pistacia lentiscus L.

In this study we present evidences of the importance of the phenological pattern on the distribution limits of the dioecious Pistacia lentiscus L. This species, though displaying a thermophilous distribution, has been proved to resist low freezing temperatures during winter. We try to explain this apparent paradox by studying the effects of an extreme cold event that occurred in December 2001 on a natural population of P. lentiscus in the NE of the Iberian Peninsula. In previous phenological studies conduced over 4 years, no spring branch damage was noticeable among population individuals. Female individuals of this species present a prolonged phenophase development which extends until early winter with the conclusion of fruit set. Therefore, we hypothesize that female plants would be more affected than male ones in terms of the following: (1) vegetative and reproductive organs survival; and (2) next-year vegetative growth and fruit production. To test this hypothesis, we selected 225 adult individuals (113 females and 112 males) in April 2002, and estimated their crown volume, percentage of frozen branches and reproductive buds, and the amount of 2001 fruits frozen. In June 2002 we evaluated, in the same individuals, the percentage of vegetative buds flushed into shoots and of reproductive buds producing infrutescences. Branch mortality was significantly higher in female plants and females with increased frost-damage displayed a higher amount of frozen fruits. The loss of reproductive buds caused a decrease in 2002 fruit production, while 2002 vegetative growth was unaffected by the degree of frost damage. These results verify most of the predictions of our hypothesis. Moreover, they suggest that the limited distribution of P. lentiscus in the cold areas of Mediterranean climate could be more determined by the long extent of the phenological activity of the crown than by its frost tolerance during winter.     

Analysis of Growth and Water Relations of Tomato Fruits in Relation to Air Vapor Pressure Deficit and Plant Fruit Load

The influence of air vapor pressure deficit (VPD) and plant fruit load on the expansion and water relations of young tomato fruits grown in a glasshouse were evaluated under summer Mediterranean conditions. The contributions of phloem, xylem and transpiration fluxes to the fruit volume increase were estimated at an hourly scale from the growth curves of intact, heat-girdled and detached fruits, measured using displacement transducers. High VPD conditions reduced the xylem influx and increased the fruit transpiration, but hardly affected the phloem influx. Net water accumulation and growth rate were reduced, and a xylem efflux even occurred during the warmest and driest hours of the day. Changes in xylem flux could be explained by variations in the gradient of water potential between stem and fruit, due to changes in stem water potential. Misting reduced air VPD and alleviated the reduction in fruit volume increase through an increase in xylem influx and a decrease in fruit transpiration. Under low fruit load, the competition for assimilates being likely reduced, the phloem flux to fruits increased, similarly to the xylem and transpiration fluxes, without any changes in the fruit water potential. However, different diurnal dynamics among treatments assume variable contributions of turgor and osmotic pressure in F3 and F6 fruits, and hypothetical short-term variations in the water potential gradient between stem and fruit, preventing xylem efflux in F3 fruits.     

The Auxins IAA and 4-Cl-IAA Differentially Modify Gibberellin Action via Ethylene Response in Developing Pea Fruit

This study explores the unique growth-regulatory roles of two naturally occurring auxins, indole-3-acetic acid (IAA) and 4-chloroindole-3-acetic acid (4-Cl-IAA), and their interactions with gibberellin (GA) during early pea (Pisum sativum L.) fruit development. We have previously shown that 4-Cl-IAA can replace the seed requirement in pea pericarp growth (length and fresh weight), whereas IAA had no effect or was inhibitory. When applied simultaneously, gibberellin (GA₃ or GA₁) and 4-Cl-IAA had a synergistic effect on pericarp growth. In the present study, we found that simultaneous application of IAA and GA₃ to deseeded pericarps inhibited GA₃-stimulated growth. The inhibitory effect of IAA on GA-stimulated growth was mimicked by treatment with ethephon (ethylene releasing agent), and the inhibitory effects of IAA and ethylene on GA-mediated growth were reversed by silver thiosulfate (STS), an ethylene action inhibitor. Although pretreatment with STS could retard senescence of IAA-treated pericarps, STS pretreatment did not lead to IAA-induced pericarp growth. Although 4-Cl-IAA stimulated growth whereas IAA was ineffective, both auxins induced similar levels of ethylene evolution. However, only 4-Cl-IAA-stimulated growth was insensitive to the effects of ethylene. Gibberellin treatment did not influence the amount of ethylene released from pericarps in the presence or absence of either auxin. We propose a growth regulatory role for 4-Cl-IAA through induction of GA biosynthesis and inhibition of ethylene action. Additionally, ethylene (IAA-induced or IAA-independent) may inhibit GA responses under physiological conditions that limit fruit growth.