Biology subjects

Barua, D.

Publications and source records attributed to Barua, D..

7 recordsLinked to original sources

bioRxiv2025

It's about time! Leaf minimum conductance determines time to reach critical thresholds for leaf dehydration in a seasonal tropical forest

O_LILeaf minimum conductance (gmin) is important in determining plant responses to drought. However, we do not understand how gmin is related to drought tolerance across species, and how important it is in determining the time to reach critical dehydration levels. C_LIO_LIIn 18 coexisting species from a seasonal tropical forest we quantified gmin to test relationships with early, moderate and severe dehydration thresholds associated with tolerance to turgor loss, breakdown of structural integrity, and disruption of cellular function, respectively. We quantified other functional and hydraulic traits to determine the major axes of trait variation in these species. C_LIO_LIVariation in gmin was the primary determinant of the time to reach critical levels of dehydration, and was unrelated to thresholds for early and severe dehydration. Surprisingly, gmin was negatively related to maximum stomatal conductance, but unrelated to other functional and hydraulic traits. C_LIO_LIThese results highlight the importance of avoiding dehydration via minimizing gmin, and suggest that avoidance, tolerance to early, and severe dehydration represent independent strategies for coping with drought. This would allow coexisting species to balance opportunities for carbon gain with costs of physiological breakdown when faced with varying intensities and durations of drought. C_LI

ecology↗

bioRxiv2023

Cell contacts and pericellular matrix in the Xenopus gastrula chordamesoderm

Convergent extension of the chordamesoderm is the best-examined gastrulation movement in Xenopus. Here we study general features of cell-cell contacts in this tissue by combining depletion of adhesion factors C-cadherin, Syndecan-4, fibronectin, and hyaluronic acid, the analysis of respective contact width spectra and contact angles, and La3+ staining of the pericellular matrix. We provide evidence that like in other gastrula tissues, cell-cell adhesion in the chordamesoderm is largely mediated by different types of pericellular matrix. Specific glycocalyx structures previously identified in Xenopus gastrula tissues are absent in chordamesoderm but other contact types like 10-20 nm wide La3+ stained structures are present instead. Knockdown of any of the adhesion factors reduces the abundance of cell contacts but not the average relative adhesiveness of the remaining ones: a decrease of adhesiveness at low contact widths is compensated by an increase of contact widths and an increase of adhesiveness proportional to width. From the adhesiveness-width relationship, we derive a model of chordamesoderm cell adhesion that involves the interdigitation of distinct pericellular matrix units. Quantitative description of pericellular matrix deployment suggests that reduced contact abundance upon adhesion factor depletion is due to some contact types becoming non-adhesive and others being lost.

cell biology↗

bioRxiv2021

Morph-specific patterns of sex organ positions in species with style length polymorphism

In style length polymorphism, morph-specific sequence of encountering male and female sex organs within a flower by pollinators can cause differences in the need to avoid self-pollination and encourage inter-morph pollination. We asked if this difference can lead to disparity in stigma-anther separation (herkogamy) between morphs and spatial match between sex organs of complementary morphs (reciprocity). Further, we tested if herkogamy, and hence the level of selfing, is fairly constant among individuals of a population. Additionally, we examined the relationship between herkogamy and reciprocity among individuals of a population to understand functional interactions between these two morphological traits. Using data on sex organ heights for >200 heterostylous species from the literature, we observed that the short-styled morph had higher herkogamy as compared to the long-styled morph indicating a higher need to avoid selfing. Reciprocity did not show a consistent difference between the upper and lower sex organs implying a strong influence of local ecological factors. In most populations, allometric relationships suggested that herkogamy and hence the level of selfing remains constant. Finally, we observed that herkogamy and reciprocity can be related among individuals of a population, sometimes indicating a potential trade-off between avoidance of self-pollination and facilitation of inter-morph pollination.

ecology↗

bioRxiv2021

Quantitative estimates of deciduousness in woody species from a seasonally dry tropical forest are related to leaf functional traits and the timing of leaf flush

Leaf phenology based classification of woody species into discrete evergreen and deciduous categories is widely used in ecology, but these categories hide important variation in leaf phenological behaviour. Few studies have examined the continuous nature of deciduousness and our understanding of variation in quantitative estimates of leaf shedding behaviour and the causes and consequences of this is limited. In this study we monitored leaf phenology in 75 woody species from a seasonally dry tropical forest to quantify three quantitative measures of deciduousness, namely: maximum canopy loss, duration of deciduousness, and average canopy loss. Based on proposed drought tolerance and drought avoidance strategies of evergreen and deciduous species, respectively, we tested whether the quantitative measures of deciduousness were related to leaf functional traits. Additionally, to understand the functional consequences of variation in deciduousness we examined relationships with the timing of leaf flushing and senescing. We found wide and continuous variation in quantitative measures of deciduousness in these coexisting species. Variation in deciduousness was related to leaf function traits, and the timing of leaf flushing. Along a continuous axis ranging from evergreen to deciduous species, increasing deciduousness was associated with more acquisitive leaf functional traits, with lower leaf mass per area and leaf dry matter content, and greater leaf nitrogen content. These results indicate that the continuous nature of deciduousness is an important component of resource acquisition strategies in woody species from seasonally dry forests.

ecology↗

bioRxiv2020

Response of whole plant water use to limiting light and water conditions are independent of each other in seedlings of seasonally dry tropical forests

How co-occurring species vary in the utilization of a shared and limited supply of water, especially in the context of other limiting resources like light, is essential for understanding processes that facilitate species coexistence and community assembly. For seedlings in a seasonally dry tropical forest that experience large heterogeny in light and water conditions, how water use, leaf physiology, and subsequently plant growth, is affected by limited water and light availability is still not well understood. In a controlled common garden experiment with four co-existing and commonly occurring dry tropical forest species, we examined how whole plant water uptake, responds to limiting water and light conditions and whether these responses are reflected in leaf physiology, and translated to growth. Water use varied dramatically in seedlings of the four species with a five-fold difference in well-watered plants grown in full sunlight. Species varied in their response to shade, but did not differ in responses to the low water treatment, possibly resulting from the strong selective force imposed by the very low water availability and the long dry period characteristic of these seasonally dry forests. Interestingly, species responses in water use, physiology, and growth in limiting water conditions were independent of light. Thus, species response to both these limiting conditions may evolve independently of each other. Responses in water use were largely congruent with responses in leaf physiology and growth. However, while magnitude of changes in leaf physiology were largely driven by light conditions, changes in whole plant water use and growth were influenced to a greater degree by the water treatment. This highlights the need to measure whole plant water use to better understand plant growth responses in these seasonally dry tropical forests.

ecology↗

bioRxiv2020

Herkogamy but not reciprocity is a better predictor of legitimate pollen transfer and fruit set in Jasminum malabaricum, a self-compatible species with stigma height dimorphism.

Premise Reciprocity and herkogamy, morphological traits that define style length polymorphisms, are thought to be critical in determining legitimate inter-morph pollen transfer in plants with style length polymorphism. However, the consequences of individual-level variation in these traits for pollen transfer and reproductive success have rarely been examined, and the relationship between these two fundamental traits remains unexplored.Methods We quantified individual-level estimates of herkogamy and reciprocity and tested the assumption that higher herkogamy and reciprocity result in higher legitimate pollen transfer and reproductive success in natural populations of Jasminum malabaricum, a species that exhibits stigma-height dimorphism. Additionally, we examined the relationship between herkogamy and reciprocity to understand potential consequences for avoiding self-pollination and encouraging legitimate pollen deposition.Results Surprisingly, reciprocity was not related to pollen load, legitimate pollen fraction or reproductive success. In contrast, herkogamy was positively associated with legitimate pollen fraction and fruit set in the long-styled morph. Interestingly, we observed a negative relationship between herkogamy and reciprocity in the long-styled morph.Conclusions Herkogamy was more important than reciprocity in increasing legitimate pollen transfer and reproductive success in J. malabaricum. Herkogamy might be particularly important in stabilising species with stigma-height dimorphism and other such polymorphic intermediates with low reciprocity, and this may allow the evolution of reciprocal arrangement of sex organs at a later stage in the pathway towards distyly. The negative relationship between herkogamy and reciprocity suggests a trade-off between avoidance of self-pollen deposition and promotion of legitimate pollen deposition.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2020

Increased variation in sex organ positions can increase reciprocity and pollination success in heterostylous plant populations

AimsThe reciprocal position of sexual organs in complementary floral morphs is central to our understanding of heterostyly. Reciprocity indices are used to quantify the spatial match between complementary sex organs, but previous indices fail to appropriately account for variation in sex organ positions among individuals in a population. The objective of this study was to examine how reciprocity and consequently reproductive success change with an increase in intra-population variation in sex organ heights. To this end, we formulated a reciprocity index that incorporates variation in sex organ positions among individuals in a population and asked if estimates of reciprocity can predict reproductive success in naturally occurring heterostylous populations. MethodsWe developed a reciprocity index that assumed pollen transfer success equalled one for a perfectly matched stigma-anther pair, and decreased to zero with increasing mismatch. Reciprocity was quantified as the average pollen transfer success for all pair-wise combinations of complementary sex organs in the population. We examined the relationship between intra-population variation and reciprocity using simulated populations that varied in the distribution of sex organ positions, and with empirical data from natural populations. We compared previously proposed indices using the simulated and natural populations, and for a subset of natural populations we tested the ability of the indices to predict reproductive success. Important FindingsIn both simulated and natural populations we observed that when differences between mean anther and stigma heights of complementary morphs are small, increasing intra-population variation in heights resulted in a monotonous decrease in reciprocity. However, when differences between mean complementary anther and stigma heights are larger, reciprocity increased, reached a peak, and then decreased with increasing variation. Previous indices failed to capture this behaviour and were largely insensitive to variation or differences in mean complementary sex organ heights. Seed set was consistently positively related to reciprocity for our index, and for two of the four previous indices. These results highlight the importance of incorporating intra-population variation in sex organ dimensions in quantifying reciprocity, and challenge the current understanding that increasing variation will always decrease reciprocity in heterostylous populations. These results may help explain why heterostylous systems exhibit, and tolerate high amounts of intra-population variation in sex organ heights.

ecology↗