Data are the pooled means of three estimates each over two years **±** standard deviation. 'p-value' denotes the significance of difference between the means by one way ANOVA statistics. a The values followed by different letters differ significantly by Duncan's multiple range test at p=0.05.

**\* Cul**: *Cassia uniflora* Mill.non Spreng ; **Snl**: *Synedrella nodiflora*(L) Gaertn; **Alt**: *Alternanthera tenella* Colla; **Eug**: *Euphorbia geniculata* Orteg.; **Ach**: *Achyranthes aspera* L.; **Bod**: *Boerhaavia erecta* L.; **Bln**: *Blainvillea acmella* L.; **Aca**: *Acalypha ciliata* Forsk.; **Tum:** *Triumfetta rhomboidea* Jacq.; **Cab**: *Cassia absus* L.; **Cfl:** *Cassia obtusifolia* L.; **Bdn**: *Bidens biternata* Lour.; **Raw:** *Rauwolfia tetraphylla* L.; **Opl:** *Oplismenus compositus* P.Beauv.

Table 4. Photosynthetic parameters of invasive and native weeds

Morphophysiological Investigations in Some Dominant Alien Invasive Weeds 33

**h h**

**Raw**

**cd d**

**Opl**

**Protein FAA**

**de**

**Bdn**

**gh gh**

**Cfl**

**bc cd <sup>c</sup> cd cd**

**Cab**

**f**

**Tum**

**gh**

**Aca**

**Weeds**

#Data columns are the pooled means of three replicates over two years with standard deviation as error bars. a Different letters at the data points denote significant difference by Duncan's multiple range test

According to Blum (1996, 1997) and Inderjit and Nilsen (2003), allelopathic action can be explained by investigating the organic compounds in plants, because they may have additive effect or joint action on various biosynthetic pathways of primary and secondary metabolites. The contents of various organic constituents existing in plants may indicate their allelopathic potential, luxuriant growth and aggressive nature. Similar explanations may be applicable for the luxuriant growth and aggressive nature, faster encroachment and dominance of *Cassia* and *Synedrella* at all the four selected sites in Pune University campus, as both the weeds were highly superior in photosynthetic pigments, different photosynthetic parameters and organic constituents like sugar, starch, proteins and free

As it is well documented that invasive and native weeds have stress tolerant abilities and sustenance to withstand harsh ecological conditions due to the presence of osmolytes, antioxidants and ROS scavenging enzymes, an attempt was made for analysis of these

The results recorded in Table 5 on various antioxidants/ osmolytes/ compatible solutes like proline, glycine betaine and phenolics revealed that *Cassia uniflora* was having highest contents. It followed by *Synedrella* and *Alternanthera.* However the results on glycine betaine

The analysis of MDA content (lipid peroxidation) revealed that *Cassia uniflora* had lowest value, which was followed by *Synedrella* and *Alternanthera.* While *Achyranthes* was lowest

The results on MSI showed that the index was highest in *Cassia uniflora* which was followed

The results reported in Table 5 on the relative water content of invasive and native weeds showed that here also *Cassia uniflora* was topmost, succeeded by *Synedrella* and

**bc**

**de**

**Bln**

**fg**

**Bod**

Fig. 3. Protein and free amino acid contentsin the invasive and native weeds

**c**

**c**

**d**

**Eug**

**Ach**

**4.9 ROS scavenging mechanism of invasive and native weeds** 

were not significant and for phenolics all the three weed species were at par.

**ab ab bc b a**

**Alt**

**b b**

**a**

**mg g**

at p<0.05.

amino acids.

parameters.

*Alternanthera*.

amongst the native weeds*.* 

by *Synedrella* and *Alternanthera.* 

**-1**

**Cul**

**Snl**

Photosynthesis is the unique process that governs the plant productivity and biomass production. Hence the increased photosynthetic rate in invasive weeds might be able to increase biomass as the rate of dry matter accumulation rate resulting into higher biomass production. All these factors might be responsible for the higher dominance of selected invasive weeds in the study area. The invasive weeds studied in the present investigation like *Cassia uniflora, Synedrella* and *Alternanthera* had shown higher rate of photosynthesis, stomatal conductance, transpiration and dry matter accumulation rate over other invasive and native weeds, which might be the basic reason for the success of invasion and dominance in the campus of University of Pune (M.S.)

### **4.8 Biochemical nature invasive and native weeds**

The results recorded on organic constituents like total sugars and starch indicated that *Cassia uniflora* had highest contents, which was followed by *Synedrella, Alternanthera* and *Bidens.* The remaining invasive and native weed species were on par for the contents of total sugars and starch, while *Cassia absus, Rauwolfia* and *Oplismenus* were at par but lower than the above mentioned weeds for starch and total sugars (Figure 2).

The invasive weeds like *Cassia uniflora* had shown highest contents of proteins and free amino acids, which was followed by *Synedrella* and *Alternanthera.* While *Bidens, Blainvillea*  and *Euphorbia* were at par. The native weed *Achyranthes* had maximum contents of proteins and free amino acids, followed by *Triumfetta* and *Boerhaavia.* While remaining weed species had comparatively very less contents of proteins and free amino acids (Figure 3).

The dominant invasive and native weeds were having comparatively higher contents of reducing and total sugars, starch, proteins etc. They further explained that the superiority in organic constituents was contributing for the luxuriant growth and allelopathic potential. The chemicals released from damaged roots, root exudates and leaf leachates such as amino acids and carbohydrates may not directly act as allelopathic agents, but they can modify the activities of allelochemicals. The maximum contents of organic constituents like total sugars and starch have also indicated the better photosynthetic efficiency of these weeds over coexisting ones. The contents of primary metabolites like sugars, carbohydrates, amino acids, proteins etc. in plants also have allelopathic potential. The higher contents of all above organic constituents in *Cassia* and *Synedrella* might be responsible for their allelopathic potential.

Fig. 2. Total sugars and starch contents in the invasive and native weeds

Photosynthesis is the unique process that governs the plant productivity and biomass production. Hence the increased photosynthetic rate in invasive weeds might be able to increase biomass as the rate of dry matter accumulation rate resulting into higher biomass production. All these factors might be responsible for the higher dominance of selected invasive weeds in the study area. The invasive weeds studied in the present investigation like *Cassia uniflora, Synedrella* and *Alternanthera* had shown higher rate of photosynthesis, stomatal conductance, transpiration and dry matter accumulation rate over other invasive and native weeds, which might be the basic reason for the success of invasion and

The results recorded on organic constituents like total sugars and starch indicated that *Cassia uniflora* had highest contents, which was followed by *Synedrella, Alternanthera* and *Bidens.* The remaining invasive and native weed species were on par for the contents of total sugars and starch, while *Cassia absus, Rauwolfia* and *Oplismenus* were at par but lower than

The invasive weeds like *Cassia uniflora* had shown highest contents of proteins and free amino acids, which was followed by *Synedrella* and *Alternanthera.* While *Bidens, Blainvillea*  and *Euphorbia* were at par. The native weed *Achyranthes* had maximum contents of proteins and free amino acids, followed by *Triumfetta* and *Boerhaavia.* While remaining weed species

The dominant invasive and native weeds were having comparatively higher contents of reducing and total sugars, starch, proteins etc. They further explained that the superiority in organic constituents was contributing for the luxuriant growth and allelopathic potential. The chemicals released from damaged roots, root exudates and leaf leachates such as amino acids and carbohydrates may not directly act as allelopathic agents, but they can modify the activities of allelochemicals. The maximum contents of organic constituents like total sugars and starch have also indicated the better photosynthetic efficiency of these weeds over coexisting ones. The contents of primary metabolites like sugars, carbohydrates, amino acids, proteins etc. in plants also have allelopathic potential. The higher contents of all above organic constituents in *Cassia* and *Synedrella* might be responsible for their allelopathic

had comparatively very less contents of proteins and free amino acids (Figure 3).

dominance in the campus of University of Pune (M.S.)

**4.8 Biochemical nature invasive and native weeds** 

potential.

**mg g**

**-1**

**Cul**

**Snl**

**Alt**

**<sup>a</sup> ab ab bc bc**

**b bc b**

**Eug**

**Ach**

**Bod**

Fig. 2. Total sugars and starch contents in the invasive and native weeds

**<sup>a</sup> <sup>a</sup>**

the above mentioned weeds for starch and total sugars (Figure 2).

**ef cd**

**f de**

**cd cd**

**Tum**

**cd bc**

**Bln**

**Aca**

**Weeds**

**f**

**Cfl**

**Bdn**

**d**

**bc**

**bc**

**g h**

**Raw**

**e e**

**Opl**

**TS Starch**

**g**

**e**

**Cab**

#Data columns are the pooled means of three replicates over two years with standard deviation as error bars. a Different letters at the data points denote significant difference by Duncan's multiple range test at p<0.05.

Fig. 3. Protein and free amino acid contentsin the invasive and native weeds

According to Blum (1996, 1997) and Inderjit and Nilsen (2003), allelopathic action can be explained by investigating the organic compounds in plants, because they may have additive effect or joint action on various biosynthetic pathways of primary and secondary metabolites. The contents of various organic constituents existing in plants may indicate their allelopathic potential, luxuriant growth and aggressive nature. Similar explanations may be applicable for the luxuriant growth and aggressive nature, faster encroachment and dominance of *Cassia* and *Synedrella* at all the four selected sites in Pune University campus, as both the weeds were highly superior in photosynthetic pigments, different photosynthetic parameters and organic constituents like sugar, starch, proteins and free amino acids.

### **4.9 ROS scavenging mechanism of invasive and native weeds**

As it is well documented that invasive and native weeds have stress tolerant abilities and sustenance to withstand harsh ecological conditions due to the presence of osmolytes, antioxidants and ROS scavenging enzymes, an attempt was made for analysis of these parameters.

The results recorded in Table 5 on various antioxidants/ osmolytes/ compatible solutes like proline, glycine betaine and phenolics revealed that *Cassia uniflora* was having highest contents. It followed by *Synedrella* and *Alternanthera.* However the results on glycine betaine were not significant and for phenolics all the three weed species were at par.

The analysis of MDA content (lipid peroxidation) revealed that *Cassia uniflora* had lowest value, which was followed by *Synedrella* and *Alternanthera.* While *Achyranthes* was lowest amongst the native weeds*.* 

The results on MSI showed that the index was highest in *Cassia uniflora* which was followed by *Synedrella* and *Alternanthera.* 

The results reported in Table 5 on the relative water content of invasive and native weeds showed that here also *Cassia uniflora* was topmost, succeeded by *Synedrella* and *Alternanthera*.

Morphophysiological Investigations in Some Dominant Alien Invasive Weeds 35

The enhancement in various antioxidants was reported by many allelopathy workers like Tambussi et al. (2000), Horling et al. (2003), Guha et al*.* (2004), Yang and Lu (2005) in different types of invasive plants growing in terrestrial and boreal forest communities of North America. The role(s) of different antioxidants and osmolytes existing in the invasive and native weeds of forest and cropland ecosystems are very much important. They have explained that the antioxidants were helpful for these weeds to become dominant over co-

The free radicals are constantly generated under stress conditions which are quenched by an efficient antioxidant network in the plant body. The complex network of such adaptive mechanisms at physiological and molecular levels cause changes in the synthesis and accumulation of various osmolytes, antioxidants and antioxidant enzymes, which provide

Proline is a major organic osmolyte accumulating in a variety of plant species in response to biotic and abiotic stresses, though its actual role in plant osmo-tolerance remains controversial. It is also thought to help in stabilization of sub-cellular structures (e.g. membranes and proteins), and to scavenge free radicals under stress conditions. Proline is known to occur widely in higher plants and normally accumulates in large quantities in

The rapid breakdown of proline upon relief of stress may provide sufficient reducing agents that support mitochondrial oxidative phosphorylation and generation of ATP for recovery from stress and repairing of stress induced damages (Zhu 2002). In response to drought or salinity stress in plants proline also helps for cytoplasmic osmotic adjustment. Accumulation of proline under stress in many plant species has been correlated with stress tolerance, and its concentration has been shown to be generally higher in stress - tolerant than in stress - sensitive plants (Ashraf and Harris 2004, Ashraf and Foolad 2007). Comparatively higher amount of proline accumulation in *Cassia* and *Synedrella* might be functioning as mentioned above providing stress tolerance to these weeds, as a result of which both the weeds were able to survive throughout the year and producing large no. of seeds even under unfavourable stress conditions. These outnumbering seeds of both the invasive weeds when germinate during favourable season, naturally establish the monothickets or pure stands which caused substitution of many natives resulting into loss

Malondialdehyde (MDA) is a product of lipid peroxidation by a thiobarbituric acid reaction. During drought conditions high activities of antioxidant enzymes are associated with lower concentration of MDA, being linked to drought tolerance (Gao et al. 2008). Like proline lowest values of MDA in *Cassia* and *Synedrella* can be linked with drought tolerance and

One of the most common responses in plants to abiotic stresses is overproduction of different types of compatible organic solutes (Serraj and Sinclair 2002), which protect the plants from stress injuries by cellular osmotic adjustment, detoxification of ROS, protection of membrane integrity and stabilization of enzymes/ proteins. The antioxidants also protect cellular components from dehydration injury. These solutes include proline, sucrose, polyols, trehalose and quaternary ammonium compounds (QACs) such as glycine-betaine, alanine-betaine, proline-betaine, choline *O*-sulfate, hydroxyproline-betaine and pipecolate-

stress tolerance to the plants (Bagul et al. 2005, Bhattacharya et al. 2009).

response to environmental stresses (Kavi Kishore et al. 2005).

of phytodiversity of Pune University campus.

betaine (Rhodes and Hanson 1993).

better survival in extremely adverse environmental conditions.

occuring plant species.

